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$PostgreSQL: pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.198 2007/12/11 19:57:32 tgl Exp $
PostgreSQL documentation
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<refentry id="APP-PSQL">
  <refmeta>
    <refentrytitle id="app-psql-title"><application>psql</application></refentrytitle>
    <manvolnum>1</manvolnum>
    <refmiscinfo>Application</refmiscinfo>
  </refmeta>

  <refnamediv>
    <refname><application>psql</application></refname>
    <refpurpose>
      <productname>PostgreSQL</productname> interactive terminal
    </refpurpose>
  </refnamediv>

 <indexterm zone="app-psql">
  <primary>psql</primary>
 </indexterm>

 <refsynopsisdiv>
  <cmdsynopsis>
   <command>psql</command>
   <arg rep="repeat"><replaceable class="parameter">option</replaceable></arg>
   <arg><replaceable class="parameter">dbname</replaceable>
   <arg><replaceable class="parameter">username</replaceable></arg></arg>
  </cmdsynopsis>
 </refsynopsisdiv>

 <refsect1>
  <title>Description</title>

    <para>
     <application>psql</application> is a terminal-based front-end to
     <productname>PostgreSQL</productname>. It enables you to type in
     queries interactively, issue them to
     <productname>PostgreSQL</productname>, and see the query results.
     Alternatively, input can be from a file. In addition, it provides a
     number of meta-commands and various shell-like features to
     facilitate writing scripts and automating a wide variety of tasks.
    </para>
 </refsect1>

 <refsect1 id="R1-APP-PSQL-3">
  <title>Options</title>

  <variablelist>
    <varlistentry>
      <term><option>-a</></term>
      <term><option>--echo-all</></term>
      <listitem>
      <para>
      Print all input lines to standard output as they are read. This is more
      useful for script processing rather than interactive mode. This is
      equivalent to setting the variable <varname>ECHO</varname> to
      <literal>all</literal>.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-A</></term>
      <term><option>--no-align</></term>
      <listitem>
      <para>
      Switches to unaligned output mode. (The default output mode is
      otherwise aligned.)
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-c <replaceable class="parameter">command</replaceable></></term>
      <term><option>--command <replaceable class="parameter">command</replaceable></></term>
      <listitem>
      <para>
      Specifies that <application>psql</application> is to execute one
      command string, <replaceable class="parameter">command</replaceable>,
      and then exit. This is useful in shell scripts.
      </para>
      <para>
      <replaceable class="parameter">command</replaceable> must be either
      a command string that is completely parsable by the server (i.e.,
      it contains no <application>psql</application> specific features),
      or a single backslash command. Thus you cannot mix
      <acronym>SQL</acronym> and <application>psql</application>
      meta-commands with this option. To achieve that, you could
      pipe the string into <application>psql</application>, like
      this: <literal>echo '\x \\ SELECT * FROM foo;' | psql</literal>.
      (<literal>\\</> is the separator meta-command.)
      </para>
      <para>
       If the command string contains multiple SQL commands, they are
       processed in a single transaction, unless there are explicit
       <command>BEGIN</>/<command>COMMIT</> commands included in the
       string to divide it into multiple transactions.  This is
       different from the behavior when the same string is fed to
       <application>psql</application>'s standard input.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-d <replaceable class="parameter">dbname</replaceable></></term>
      <term><option>--dbname <replaceable class="parameter">dbname</replaceable></></term>
      <listitem>
      <para>
       Specifies the name of the database to connect to. This is
       equivalent to specifying <replaceable
       class="parameter">dbname</replaceable> as the first non-option
       argument on the command line.
      </para>
      <para>
       If this parameter contains an <symbol>=</symbol> sign, it is treated as a
       <parameter>conninfo</parameter> string. See <xref linkend="libpq-connect"> for more information.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-e</></term>
      <term><option>--echo-queries</></term>
      <listitem>
      <para>
      Copy all SQL commands sent to the server to standard output as well.
      This is equivalent
      to setting the variable <varname>ECHO</varname> to
      <literal>queries</literal>.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-E</></term>
      <term><option>--echo-hidden</></term>
      <listitem>
      <para>
      Echo the actual queries generated by <command>\d</command> and other backslash
      commands. You can use this to study <application>psql</application>'s
      internal operations. This is equivalent to
      setting the variable <varname>ECHO_HIDDEN</varname> from within
      <application>psql</application>.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-f <replaceable class="parameter">filename</replaceable></></term>
      <term><option>--file <replaceable class="parameter">filename</replaceable></></term>
      <listitem>
      <para>
      Use the file <replaceable class="parameter">filename</replaceable>
      as the source of commands instead of reading commands interactively.
      After the file is processed, <application>psql</application>
      terminates. This is in many ways equivalent to the internal
      command <command>\i</command>.
      </para>

      <para>
       If <replaceable>filename</replaceable> is <literal>-</literal>
       (hyphen), then standard input is read.
      </para>

      <para>
      Using this option is subtly different from writing <literal>psql
      &lt; <replaceable
      class="parameter">filename</replaceable></literal>. In general,
      both will do what you expect, but using <literal>-f</literal>
      enables some nice features such as error messages with line
      numbers. There is also a slight chance that using this option will
      reduce the start-up overhead. On the other hand, the variant using
      the shell's input redirection is (in theory) guaranteed to yield
      exactly the same output that you would have gotten had you entered
      everything by hand.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-F <replaceable class="parameter">separator</replaceable></></term>
      <term><option>--field-separator <replaceable class="parameter">separator</replaceable></></term>
      <listitem>
      <para>
      Use <replaceable class="parameter">separator</replaceable> as the
      field separator for unaligned output. This is equivalent to
      <command>\pset fieldsep</command> or <command>\f</command>.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-h <replaceable class="parameter">hostname</replaceable></></term>
      <term><option>--host <replaceable class="parameter">hostname</replaceable></></term>
      <listitem>
      <para>
      Specifies the host name of the machine on which the
      server is running. If the value begins
      with a slash, it is used as the directory for the Unix-domain
      socket.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-H</></term>
      <term><option>--html</></term>
      <listitem>
      <para>
      Turn on <acronym>HTML</acronym> tabular output. This is
      equivalent to <literal>\pset format html</literal> or the
      <command>\H</command> command.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-l</></term>
      <term><option>--list</></term>
      <listitem>
      <para>
      List all available databases, then exit. Other non-connection
      options are ignored. This is similar to the internal command
      <command>\list</command>.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-L <replaceable class="parameter">filename</replaceable></></term>
      <term><option>--log-file <replaceable class="parameter">filename</replaceable></></term>
      <listitem>
      <para>
       Write all query output into file <replaceable
       class="parameter">filename</replaceable>, in addition to the
       normal output destination.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-o <replaceable class="parameter">filename</replaceable></></term>
      <term><option>--output <replaceable class="parameter">filename</replaceable></></term>
      <listitem>
      <para>
      Put all query output into file <replaceable
      class="parameter">filename</replaceable>. This is equivalent to
      the command <command>\o</command>.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-p <replaceable class="parameter">port</replaceable></></term>
      <term><option>--port <replaceable class="parameter">port</replaceable></></term>
      <listitem>
      <para>
      Specifies the TCP port or the local Unix-domain
      socket file extension on which the server is listening for
      connections. Defaults to the value of the <envar>PGPORT</envar>
      environment variable or, if not set, to the port specified at
      compile time, usually 5432.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-P <replaceable class="parameter">assignment</replaceable></></term>
      <term><option>--pset <replaceable class="parameter">assignment</replaceable></></term>
      <listitem>
      <para>
      Allows you to specify printing options in the style of
      <command>\pset</command> on the command line. Note that here you
      have to separate name and value with an equal sign instead of a
      space. Thus to set the output format to LaTeX, you could write
      <literal>-P format=latex</literal>.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-q</></term>
      <term><option>--quiet</></term>
      <listitem>
      <para>
      Specifies that <application>psql</application> should do its work
      quietly. By default, it prints welcome messages and various
      informational output. If this option is used, none of this
      happens. This is useful with the <option>-c</option> option.
      Within <application>psql</application> you can also set the
      <varname>QUIET</varname> variable to achieve the same effect.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-R <replaceable class="parameter">separator</replaceable></></term>
      <term><option>--record-separator <replaceable class="parameter">separator</replaceable></></term>
      <listitem>
      <para>
      Use <replaceable class="parameter">separator</replaceable> as the
      record separator for unaligned output. This is equivalent to the
      <command>\pset recordsep</command> command.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-s</></term>
      <term><option>--single-step</></term>
      <listitem>
      <para>
      Run in single-step mode. That means the user is prompted before
      each command is sent to the server, with the option to cancel
      execution as well. Use this to debug scripts.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-S</></term>
      <term><option>--single-line</></term>
      <listitem>
      <para>
      Runs in single-line mode where a newline terminates an SQL command, as a
      semicolon does.
      </para>

      <note>
      <para>
      This mode is provided for those who insist on it, but you are not
      necessarily encouraged to use it. In particular, if you mix
      <acronym>SQL</acronym> and meta-commands on a line the order of
      execution might not always be clear to the inexperienced user.
      </para>
      </note>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-t</></term>
      <term><option>--tuples-only</></term>
      <listitem>
      <para>
      Turn off printing of column names and result row count footers,
      etc. This is equivalent to the <command>\t</command> command.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-T <replaceable class="parameter">table_options</replaceable></></term>
      <term><option>--table-attr <replaceable class="parameter">table_options</replaceable></></term>
      <listitem>
      <para>
      Allows you to specify options to be placed within the
      <acronym>HTML</acronym> <sgmltag>table</sgmltag> tag. See
      <command>\pset</command> for details.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-U <replaceable class="parameter">username</replaceable></></term>
      <term><option>--username <replaceable class="parameter">username</replaceable></></term>
      <listitem>
      <para>
      Connect to the database as the user <replaceable
      class="parameter">username</replaceable> instead of the default.
      (You must have permission to do so, of course.)
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-v <replaceable class="parameter">assignment</replaceable></></term>
      <term><option>--set <replaceable class="parameter">assignment</replaceable></></term>
      <term><option>--variable <replaceable class="parameter">assignment</replaceable></></term>
      <listitem>
      <para>
      Perform a variable assignment, like the <command>\set</command>
      internal command. Note that you must separate name and value, if
      any, by an equal sign on the command line. To unset a variable,
      leave off the equal sign. To just set a variable without a value,
      use the equal sign but leave off the value. These assignments are
      done during a very early stage of start-up, so variables reserved
      for internal purposes might get overwritten later.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-V</></term>
      <term><option>--version</></term>
      <listitem>
      <para>
      Print the <application>psql</application> version and exit.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-W</></term>
      <term><option>--password</></term>
      <listitem>
      <para>
       Force <application>psql</application> to prompt for a
       password before connecting to a database.  
      </para>

      <para>
       This option is never essential, since <application>psql</application>
       will automatically prompt for a password if the server demands
       password authentication.  However, <application>psql</application>
       will waste a connection attempt finding out that the server wants a
       password.  In some cases it is worth typing <option>-W</> to avoid
       the extra connection attempt.
      </para>

      <para>
       Note that this option will remain set for the entire session,
       and so it affects uses of the meta-command
       <command>\connect</command> as well as the initial connection attempt.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-x</></term>
      <term><option>--expanded</></term>
      <listitem>
      <para>
      Turn on the expanded table formatting mode. This is equivalent to the
      <command>\x</command> command.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-X,</></term>
      <term><option>--no-psqlrc</></term>
      <listitem>
      <para>
      Do not read the start-up file (neither the system-wide
      <filename>psqlrc</filename> file nor the user's
      <filename>~/.psqlrc</filename> file).
      </para>
      </listitem>
    </varlistentry>

     <varlistentry>
      <term><option>-1</option></term>
      <term><option>--single-transaction</option></term>
      <listitem>
       <para>
        When <application>psql</application> executes a script with the
        <option>-f</> option, adding this option wraps
        <command>BEGIN</>/<command>COMMIT</> around the script to execute it
        as a single transaction.  This ensures that either all the commands
        complete successfully, or no changes are applied.  
       </para>

       <para>
        If the script itself uses <command>BEGIN</>, <command>COMMIT</>,
        or <command>ROLLBACK</>, this option will not have the desired
        effects.
        Also, if the script contains any command that cannot be executed
        inside a transaction block, specifying this option will cause that
        command (and hence the whole transaction) to fail.
       </para>
      </listitem>
     </varlistentry>

    <varlistentry>
      <term><option>-?</></term>
      <term><option>--help</></term>
      <listitem>
      <para>
      Show help about <application>psql</application> command line
      arguments, and exit.
      </para>
      </listitem>
    </varlistentry>
  </variablelist>
 </refsect1>


 <refsect1>
  <title>Exit Status</title>

  <para>
   <application>psql</application> returns 0 to the shell if it
   finished normally, 1 if a fatal error of its own (out of memory,
   file not found) occurs, 2 if the connection to the server went bad
   and the session was not interactive, and 3 if an error occurred in a
   script and the variable <varname>ON_ERROR_STOP</varname> was set.
  </para>
 </refsect1>


 <refsect1>
  <title>Usage</title>

  <refsect2 id="R2-APP-PSQL-connecting">
    <title>Connecting To A Database</title>

    <para>
    <application>psql</application> is a regular
    <productname>PostgreSQL</productname> client application. In order
    to connect to a database you need to know the name of your target
    database, the host name and port number of the server and what user
    name you want to connect as. <application>psql</application> can be
    told about those parameters via command line options, namely
    <option>-d</option>, <option>-h</option>, <option>-p</option>, and
    <option>-U</option> respectively. If an argument is found that does
    not belong to any option it will be interpreted as the database name
    (or the user name, if the database name is already given). Not all
    these options are required; there are useful defaults. If you omit the host
    name, <application>psql</> will connect via a Unix-domain socket
    to a server on the local host, or via TCP/IP to <literal>localhost</> on
    machines that don't have Unix-domain sockets. The default port number is
    determined at compile time.
    Since the database server uses the same default, you will not have
    to specify the port in most cases. The default user name is your
    Unix user name, as is the default database name. Note that you cannot
    just connect to any database under any user name. Your database
    administrator should have informed you about your access rights.
    </para>

    <para>
    When the defaults aren't quite right, you can save yourself
    some typing by setting the environment variables
    <envar>PGDATABASE</envar>, <envar>PGHOST</envar>,
    <envar>PGPORT</envar> and/or <envar>PGUSER</envar> to appropriate
    values. (For additional environment variables, see <xref
    linkend="libpq-envars">.) It is also convenient to have a
    <filename>~/.pgpass</> file to avoid regularly having to type in
    passwords. See <xref linkend="libpq-pgpass"> for more information.
    </para>

    <para>
     An alternative way to specify connection parameters is in a
     <parameter>conninfo</parameter> string, which is used instead of a 
     database name. This mechanism give you very wide control over the 
     connection. For example:
<programlisting>
$ <userinput>psql "service=myservice sslmode=require"</userinput>
</programlisting>
     This way you can also use LDAP for connection parameter lookup as
     described in <xref linkend="libpq-ldap">.
     See <xref linkend="libpq-connect"> for more information on all the
     available connection options.
    </para>

    <para>
    If the connection could not be made for any reason (e.g., insufficient
    privileges, server is not running on the targeted host, etc.),
    <application>psql</application> will return an error and terminate.
    </para>
  </refsect2>

  <refsect2 id="R2-APP-PSQL-4">
    <title>Entering SQL Commands</title>

    <para>
    In normal operation, <application>psql</application> provides a
    prompt with the name of the database to which
    <application>psql</application> is currently connected, followed by
    the string <literal>=&gt;</literal>. For example:
<programlisting>
$ <userinput>psql testdb</userinput>
Welcome to psql &version;, the PostgreSQL interactive terminal.

Type:  \copyright for distribution terms
       \h for help with SQL commands
       \? for help with psql commands
       \g or terminate with semicolon to execute query
       \q to quit

testdb=&gt;
</programlisting>
    </para>

    <para>
    At the prompt, the user can type in <acronym>SQL</acronym> commands.
    Ordinarily, input lines are sent to the server when a
    command-terminating semicolon is reached. An end of line does not
    terminate a command.  Thus commands can be spread over several lines for
    clarity. If the command was sent and executed without error, the results
    of the command are displayed on the screen.
    </para>

    <para>
    Whenever a command is executed, <application>psql</application> also polls
    for asynchronous notification events generated by
    <xref linkend="SQL-LISTEN" endterm="SQL-LISTEN-title"> and
    <xref linkend="SQL-NOTIFY" endterm="SQL-NOTIFY-title">.
    </para>
  </refsect2>

  <refsect2>
    <title>Meta-Commands</title>

    <para>
    Anything you enter in <application>psql</application> that begins
    with an unquoted backslash is a <application>psql</application>
    meta-command that is processed by <application>psql</application>
    itself. These commands help make
    <application>psql</application> more useful for administration or
    scripting. Meta-commands are more commonly called slash or backslash
    commands.
    </para>

    <para>
    The format of a <application>psql</application> command is the backslash,
    followed immediately by a command verb, then any arguments. The arguments
    are separated from the command verb and each other by any number of
    whitespace characters.
    </para>

    <para>
    To include whitespace into an argument you can quote it with a
    single quote. To include a single quote into such an argument,
    use two single quotes. Anything contained in single quotes is
    furthermore subject to C-like substitutions for
    <literal>\n</literal> (new line), <literal>\t</literal> (tab),
    <literal>\</literal><replaceable>digits</replaceable> (octal), and
    <literal>\x</literal><replaceable>digits</replaceable> (hexadecimal).
    </para>

    <para>
    If an unquoted argument begins with a colon (<literal>:</literal>),
    it is taken as a <application>psql</> variable and the value of the
    variable is used as the argument instead.
    </para>

    <para>
    Arguments that are enclosed in backquotes (<literal>`</literal>)
    are taken as a command line that is passed to the shell. The
    output of the command (with any trailing newline removed) is taken
    as the argument value. The above escape sequences also apply in
    backquotes.
    </para>

    <para>
    Some commands take an <acronym>SQL</acronym> identifier (such as a
    table name) as argument. These arguments follow the syntax rules
    of <acronym>SQL</acronym>: Unquoted letters are forced to
    lowercase, while double quotes (<literal>"</>) protect letters
    from case conversion and allow incorporation of whitespace into
    the identifier.  Within double quotes, paired double quotes reduce
    to a single double quote in the resulting name.  For example,
    <literal>FOO"BAR"BAZ</> is interpreted as <literal>fooBARbaz</>,
    and <literal>"A weird"" name"</> becomes <literal>A weird"
    name</>.
    </para>

    <para>
    Parsing for arguments stops when another unquoted backslash occurs.
    This is taken as the beginning of a new meta-command. The special
    sequence <literal>\\</literal> (two backslashes) marks the end of
    arguments and continues parsing <acronym>SQL</acronym> commands, if
    any. That way <acronym>SQL</acronym> and
    <application>psql</application> commands can be freely mixed on a
    line. But in any case, the arguments of a meta-command cannot
    continue beyond the end of the line.
    </para>

    <para>
    The following meta-commands are defined:

    <variablelist>
      <varlistentry>
        <term><literal>\a</literal></term>
        <listitem>
        <para>
        If the current table output format is unaligned, it is switched to aligned.
        If it is not unaligned, it is set to unaligned. This command is
        kept for backwards compatibility. See <command>\pset</command> for a
        more general solution.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
       <term><literal>\cd [ <replaceable>directory</replaceable> ]</literal></term>
       <listitem>
        <para>
         Changes the current working directory to
         <replaceable>directory</replaceable>. Without argument, changes
         to the current user's home directory.
        </para>

        <tip>
         <para>
          To print your current working directory, use <literal>\!pwd</literal>.
         </para>
        </tip>
       </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\C [ <replaceable class="parameter">title</replaceable> ]</literal></term>
        <listitem>
        <para>
        Sets the title of any tables being printed as the result of a
        query or unset any such title. This command is equivalent to
        <literal>\pset title <replaceable
        class="parameter">title</replaceable></literal>. (The name of
        this command derives from <quote>caption</quote>, as it was
        previously only used to set the caption in an
        <acronym>HTML</acronym> table.)
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\connect</literal> (or <literal>\c</literal>) <literal>[ <replaceable class="parameter">dbname</replaceable> [ <replaceable class="parameter">username</replaceable> ] [ <replaceable class="parameter">host</replaceable> ] [ <replaceable class="parameter">port</replaceable> ] ]</literal></term>
        <listitem>
        <para>
        Establishes a new connection to a <productname>PostgreSQL</>
        server. If the new connection is successfully made, the
        previous connection is closed. If any of <replaceable
        class="parameter">dbname</replaceable>, <replaceable
        class="parameter">username</replaceable>, <replaceable
        class="parameter">host</replaceable> or <replaceable
        class="parameter">port</replaceable> are omitted or specified
        as <literal>-</literal>, the value of that parameter from the
        previous connection is used. If there is no previous
        connection, the <application>libpq</application> default for
        the parameter's value is used.
        </para>

        <para>
        If the connection attempt failed (wrong user name, access
        denied, etc.), the previous connection will only be kept if
        <application>psql</application> is in interactive mode. When
        executing a non-interactive script, processing will
        immediately stop with an error. This distinction was chosen as
        a user convenience against typos on the one hand, and a safety
        mechanism that scripts are not accidentally acting on the
        wrong database on the other hand.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\copy { <replaceable class="parameter">table</replaceable> [ ( <replaceable class="parameter">column_list</replaceable> ) ] | ( <replaceable class="parameter">query</replaceable> ) }
        { <literal>from</literal> | <literal>to</literal> }
        { <replaceable class="parameter">filename</replaceable> | stdin | stdout | pstdin | pstdout }
        [ with ]
            [ binary ]
            [ oids ]
            [ delimiter [ as ] '<replaceable class="parameter">character</replaceable>' ]
            [ null [ as ] '<replaceable class="parameter">string</replaceable>' ]
            [ csv
              [ header ]
              [ quote [ as ] '<replaceable class="parameter">character</replaceable>' ]
              [ escape [ as ] '<replaceable class="parameter">character</replaceable>' ]
              [ force quote <replaceable class="parameter">column_list</replaceable> ]
              [ force not null <replaceable class="parameter">column_list</replaceable> ] ]</literal>
        </term>

        <listitem>
        <para>
        Performs a frontend (client) copy. This is an operation that
        runs an <acronym>SQL</acronym> <xref linkend="SQL-COPY"
        endterm="SQL-COPY-title"> command, but instead of the server
        reading or writing the specified file,
        <application>psql</application> reads or writes the file and
        routes the data between the server and the local file system.
        This means that file accessibility and privileges are those of
        the local user, not the server, and no SQL superuser
        privileges are required.
        </para>

        <para>
        The syntax of the command is similar to that of the
        <acronym>SQL</acronym> <xref linkend="sql-copy"
        endterm="sql-copy-title"> command.  Note that, because of this,
        special parsing rules apply to the <command>\copy</command>
        command. In particular, the variable substitution rules and
        backslash escapes do not apply.
        </para>

        <para>
        <literal>\copy ... from stdin | to stdout</literal>
        reads/writes based on the command input and output respectively.
        All rows are read from the same source that issued the command,
        continuing until <literal>\.</literal> is read or the stream
        reaches <acronym>EOF</>. Output is sent to the same place as
        command output. To read/write from
        <application>psql</application>'s standard input or output, use
        <literal>pstdin</> or <literal>pstdout</>. This option is useful
        for populating tables in-line within a SQL script file.
        </para>

        <tip>
        <para>
        This operation is not as efficient as the <acronym>SQL</acronym>
        <command>COPY</command> command because all data must pass
        through the client/server connection. For large
        amounts of data the <acronym>SQL</acronym> command might be preferable.
        </para>
        </tip>

        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\copyright</literal></term>
        <listitem>
        <para>
        Shows the copyright and distribution terms of
        <productname>PostgreSQL</productname>.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\d [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <term><literal>\d+ [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>

        <listitem>
        <para>
        For each relation (table, view, index, or sequence) matching the
        <replaceable class="parameter">pattern</replaceable>, show all
        columns, their types, the tablespace (if not the default) and any special
        attributes such as <literal>NOT NULL</literal> or defaults, if
        any. Associated indexes, constraints, rules, and triggers are
        also shown, as is the view definition if the relation is a view.
        (<quote>Matching the pattern</> is defined below.)
        </para>

        <para>
        The command form <literal>\d+</literal> is identical, except that
        more information is displayed: any comments associated with the
        columns of the table are shown, as is the presence of OIDs in the
        table.
        </para>

        <note>
        <para>
        If <command>\d</command> is used without a
        <replaceable class="parameter">pattern</replaceable> argument, it is
        equivalent to <command>\dtvs</command> which will show a list of
        all tables, views, and sequences. This is purely a convenience
        measure.
        </para>
        </note>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\da [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>

        <listitem>
        <para>
        Lists all available aggregate functions, together with their
        return type and the data types they operate on. If <replaceable
        class="parameter">pattern</replaceable>
        is specified, only aggregates whose names match the pattern are shown.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\db [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <term><literal>\db+ [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>

        <listitem>
        <para>
        Lists all available tablespaces. If <replaceable
        class="parameter">pattern</replaceable>
        is specified, only tablespaces whose names match the pattern are shown.
        If <literal>+</literal> is appended to the command name, each object 
        is listed with its associated permissions.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dc [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
        Lists all available conversions between character-set encodings.
        If <replaceable class="parameter">pattern</replaceable>
        is specified, only conversions whose names match the pattern are
        listed.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dC</literal></term>
        <listitem>
        <para>
        Lists all available type casts.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dd [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
        Shows the descriptions of objects matching the <replaceable
        class="parameter">pattern</replaceable>, or of all visible objects if
        no argument is given.  But in either case, only objects that have
        a description are listed.
        (<quote>Object</quote> covers aggregates, functions, operators,
        types, relations (tables, views, indexes, sequences, large
        objects), rules, and triggers.) For example:
<programlisting>
=&gt; <userinput>\dd version</userinput>
                     Object descriptions
   Schema   |  Name   |  Object  |        Description
------------+---------+----------+---------------------------
 pg_catalog | version | function | PostgreSQL version string
(1 row)
</programlisting>
        </para>

        <para>
        Descriptions for objects can be created with the <xref
        linkend="sql-comment" endterm="sql-comment-title">
        <acronym>SQL</acronym> command.
       </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dD [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
        Lists all available domains. If <replaceable
        class="parameter">pattern</replaceable>
        is specified, only matching domains are shown.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\df [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <term><literal>\df+ [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>

        <listitem>
        <para>
        Lists available functions, together with their argument and
        return types. If <replaceable
        class="parameter">pattern</replaceable>
        is specified, only functions whose names match the pattern are shown.
        If the form <literal>\df+</literal> is used, additional information about
        each function, including volatility, language, source code and description, is shown.
        </para>

        <note>
        <para>
        To look up functions taking argument or returning values of a specific
        type, use your pager's search capability to scroll through the <literal>\df</>
        output.
        </para>

        <para>
        To reduce clutter, <literal>\df</> does not show data type I/O
        functions.  This is implemented by ignoring functions that accept
        or return type <type>cstring</>.
        </para>
        </note>

        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dF [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <term><literal>\dF+ [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
         Lists available text search configurations.
         If <replaceable class="parameter">pattern</replaceable> is specified,
         only configurations whose names match the pattern are shown.
         If the form <literal>\dF+</literal> is used, a full description of
         each configuration is shown, including the underlying text search
         parser and the dictionary list for each parser token type.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\dFd [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <term><literal>\dFd+ [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
         Lists available text search dictionaries.
         If <replaceable class="parameter">pattern</replaceable> is specified,
         only dictionaries whose names match the pattern are shown.
         If the form <literal>\dFd+</literal> is used, additional information
         is shown about each selected dictionary, including the underlying
         text search template and the option values.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\dFp [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <term><literal>\dFp+ [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
         Lists available text search parsers.
         If <replaceable class="parameter">pattern</replaceable> is specified,
         only parsers whose names match the pattern are shown.
         If the form <literal>\dFp+</literal> is used, a full description of
         each parser is shown, including the underlying functions and the
         list of recognized token types.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\dFt [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <term><literal>\dFt+ [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
         Lists available text search templates.
         If <replaceable class="parameter">pattern</replaceable> is specified,
         only templates whose names match the pattern are shown.
         If the form <literal>\dFt+</literal> is used, additional information
         is shown about each template, including the underlying function names.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dg [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
        Lists all database roles. If <replaceable
        class="parameter">pattern</replaceable> is specified, only
        those roles whose names match the pattern are listed.
        (This command is now effectively the same as <literal>\du</>.)
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\distvS [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>

        <listitem>
        <para>
        This is not the actual command name: the letters
        <literal>i</literal>, <literal>s</literal>,
        <literal>t</literal>, <literal>v</literal>,
        <literal>S</literal> stand for index, sequence, table, view,
        and system table, respectively. You can specify any or all of
        these letters, in any order, to obtain a listing of all the
        matching objects.  The letter <literal>S</literal> restricts
        the listing to system objects; without <literal>S</literal>,
        only non-system objects are shown.  If <literal>+</literal> is
        appended to the command name, each object is listed with its
        associated description, if any.
        </para>

        <para>
        If <replaceable class="parameter">pattern</replaceable> is
        specified, only objects whose names match the pattern are listed.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dl</literal></term>
        <listitem>
        <para>
        This is an alias for <command>\lo_list</command>, which shows a
        list of large objects.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dn [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <term><literal>\dn+ [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>

        <listitem>
        <para>
        Lists all available schemas (namespaces). If <replaceable
        class="parameter">pattern</replaceable> (a regular expression)
        is specified, only schemas whose names match the pattern are listed.
        Non-local temporary schemas are suppressed.  If <literal>+</literal>
        is appended to the command name, each object is listed with its associated
        permissions and description, if any.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\do [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
        Lists available operators with their operand and return types.
        If <replaceable class="parameter">pattern</replaceable> is
        specified, only operators whose names match the pattern are listed.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dp [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
        Produces a list of all available tables, views and sequences with their
        associated access privileges.
        If <replaceable class="parameter">pattern</replaceable> is
        specified, only tables, views and sequences whose names match the pattern are listed.
        </para>

        <para>
        The <xref linkend="sql-grant" endterm="sql-grant-title"> and
        <xref linkend="sql-revoke" endterm="sql-revoke-title">
        commands are used to set access privileges.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dT [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <term><literal>\dT+ [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
        Lists all data types or only those that match <replaceable
        class="parameter">pattern</replaceable>. The command form
        <literal>\dT+</literal> shows extra information.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\du [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
        Lists all database roles, or only those that match <replaceable
        class="parameter">pattern</replaceable>.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\edit</literal> (or <literal>\e</literal>) <literal>[ <replaceable class="parameter">filename</replaceable> ]</literal></term>

        <listitem>
        <para>
        If <replaceable class="parameter">filename</replaceable> is
        specified, the file is edited; after the editor exits, its
        content is copied back to the query buffer. If no argument is
        given, the current query buffer is copied to a temporary file
        which is then edited in the same fashion.
        </para>

        <para>
        The new query buffer is then re-parsed according to the normal
        rules of <application>psql</application>, where the whole buffer
        is treated as a single line. (Thus you cannot make scripts this
        way. Use <command>\i</command> for that.) This means also that
        if the query ends with (or rather contains) a semicolon, it is
        immediately executed. In other cases it will merely wait in the
        query buffer.
        </para>

        <tip>
        <para>
        <application>psql</application> searches the environment
        variables <envar>PSQL_EDITOR</envar>, <envar>EDITOR</envar>, and
        <envar>VISUAL</envar> (in that order) for an editor to use. If
        all of them are unset, <filename>vi</filename> is used on Unix
        systems, <filename>notepad.exe</filename> on Windows systems.
        </para>
        </tip>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\echo <replaceable class="parameter">text</replaceable> [ ... ]</literal></term>
        <listitem>
        <para>
        Prints the arguments to the standard output, separated by one
        space and followed by a newline. This can be useful to
        intersperse information in the output of scripts. For example:
<programlisting>
=&gt; <userinput>\echo `date`</userinput>
Tue Oct 26 21:40:57 CEST 1999
</programlisting>
        If the first argument is an unquoted <literal>-n</literal> the trailing
        newline is not written.
        </para>

        <tip>
        <para>
        If you use the <command>\o</command> command to redirect your
        query output you might wish to use <command>\qecho</command>
        instead of this command.
        </para>
        </tip>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\encoding [ <replaceable class="parameter">encoding</replaceable> ]</literal></term>

        <listitem>
        <para>
        Sets the client character set encoding.  Without an argument, this command
        shows the current encoding.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\f [ <replaceable class="parameter">string</replaceable> ]</literal></term>

        <listitem>
        <para>
        Sets the field separator for unaligned query output. The default
        is the vertical bar (<literal>|</literal>). See also
        <command>\pset</command> for a generic way of setting output
        options.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\g</literal> [ { <replaceable class="parameter">filename</replaceable> | <literal>|</literal><replaceable class="parameter">command</replaceable> } ]</term>

        <listitem>
        <para>
        Sends the current query input buffer to the server and
        optionally stores the query's output in <replaceable
        class="parameter">filename</replaceable> or pipes the output
        into a separate Unix shell executing <replaceable
        class="parameter">command</replaceable>. A bare
        <literal>\g</literal> is virtually equivalent to a semicolon. A
        <literal>\g</literal> with argument is a <quote>one-shot</quote>
        alternative to the <command>\o</command> command.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\help</literal> (or <literal>\h</literal>) <literal>[ <replaceable class="parameter">command</replaceable> ]</literal></term>
        <listitem>
        <para>
        Gives syntax help on the specified <acronym>SQL</acronym>
        command. If <replaceable class="parameter">command</replaceable>
        is not specified, then <application>psql</application> will list
        all the commands for which syntax help is available. If
        <replaceable class="parameter">command</replaceable> is an
        asterisk (<literal>*</literal>), then syntax help on all
        <acronym>SQL</acronym> commands is shown.
        </para>

        <note>
        <para>
        To simplify typing, commands that consists of several words do
        not have to be quoted. Thus it is fine to type <userinput>\help
        alter table</userinput>.
        </para>
        </note>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\H</literal></term>
        <listitem>
        <para>
        Turns on <acronym>HTML</acronym> query output format. If the
        <acronym>HTML</acronym> format is already on, it is switched
        back to the default aligned text format. This command is for
        compatibility and convenience, but see <command>\pset</command>
        about setting other output options.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\i <replaceable class="parameter">filename</replaceable></literal></term>
        <listitem>
        <para>
        Reads input from the file <replaceable
        class="parameter">filename</replaceable> and executes it as
        though it had been typed on the keyboard.
        </para>
        <note>
        <para>
        If you want to see the lines on the screen as they are read you
        must set the variable <varname>ECHO</varname> to
        <literal>all</literal>.
        </para>
        </note>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\l</literal> (or <literal>\list</literal>)</term>
        <term><literal>\l+</literal> (or <literal>\list+</literal>)</term>
        <listitem>
        <para>
        List the names, owners, and character set encodings of all the databases in
        the server. If <literal>+</literal> is appended to the command
        name, database descriptions are also displayed.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\lo_export <replaceable class="parameter">loid</replaceable> <replaceable class="parameter">filename</replaceable></literal></term>

        <listitem>
        <para>
        Reads the large object with <acronym>OID</acronym> <replaceable
        class="parameter">loid</replaceable> from the database and
        writes it to <replaceable
        class="parameter">filename</replaceable>. Note that this is
        subtly different from the server function
        <function>lo_export</function>, which acts with the permissions
        of the user that the database server runs as and on the server's
        file system.
        </para>
        <tip>
        <para>
        Use <command>\lo_list</command> to find out the large object's
        <acronym>OID</acronym>.
        </para>
        </tip>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\lo_import <replaceable class="parameter">filename</replaceable> [ <replaceable class="parameter">comment</replaceable> ]</literal></term>

        <listitem>
        <para>
        Stores the file into a <productname>PostgreSQL</productname>
        large object. Optionally, it associates the given
        comment with the object. Example:
<programlisting>
foo=&gt; <userinput>\lo_import '/home/peter/pictures/photo.xcf' 'a picture of me'</userinput>
lo_import 152801
</programlisting>
        The response indicates that the large object received object
        ID 152801, which can be used to access the newly-created large
        object in the future. For the sake of readability, it is
        recommended to always associate a human-readable comment with
        every object. Both OIDs and comments can be viewed with the
        <command>\lo_list</command> command.
        </para>

        <para>
        Note that this command is subtly different from the server-side
        <function>lo_import</function> because it acts as the local user
        on the local file system, rather than the server's user and file
        system.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\lo_list</literal></term>
        <listitem>
        <para>
        Shows a list of all <productname>PostgreSQL</productname>
        large objects currently stored in the database,
        along with any comments provided for them.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\lo_unlink <replaceable class="parameter">loid</replaceable></literal></term>

        <listitem>
        <para>
        Deletes the large object with <acronym>OID</acronym>
        <replaceable class="parameter">loid</replaceable> from the
        database.
        </para>

        <tip>
        <para>
        Use <command>\lo_list</command> to find out the large object's
        <acronym>OID</acronym>.
        </para>
        </tip>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\o</literal> [ {<replaceable class="parameter">filename</replaceable> | <literal>|</literal><replaceable class="parameter">command</replaceable>} ]</term>

        <listitem>
        <para>
        Saves future query results to the file <replaceable
        class="parameter">filename</replaceable> or pipes future results
        into a separate Unix shell to execute <replaceable
        class="parameter">command</replaceable>. If no arguments are
        specified, the query output will be reset to the standard output.
        </para>

        <para>
        <quote>Query results</quote> includes all tables, command
        responses, and notices obtained from the database server, as
        well as output of various backslash commands that query the
        database (such as <command>\d</command>), but not error
        messages.
        </para>

        <tip>
        <para>
        To intersperse text output in between query results, use
        <command>\qecho</command>.
        </para>
        </tip>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\p</literal></term>
        <listitem>
        <para>
        Print the current query buffer to the standard output.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\password [ <replaceable class="parameter">username</replaceable> ]</literal></term>
        <listitem>
        <para>
        Changes the password of the specified user (by default, the current
        user).  This command prompts for the new password, encrypts it, and
        sends it to the server as an <command>ALTER ROLE</> command.  This
        makes sure that the new password does not appear in cleartext in the
        command history, the server log, or elsewhere.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\prompt [ <replaceable class="parameter">text</replaceable> ] <replaceable class="parameter">name</replaceable></literal></term>
        <listitem>
        <para>
         Prompts the user to set variable <replaceable
         class="parameter">name</>.  An optional prompt, <replaceable
         class="parameter">text</>, can be specified.  (For multi-word
         prompts, use single-quotes.)
        </para>

        <para>
         By default, <literal>\prompt</> uses the terminal for input and
         output.  However, if the <option>-f</> command line switch is
         used, <literal>\prompt</> uses standard input and standard output.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\pset <replaceable class="parameter">parameter</replaceable> [ <replaceable class="parameter">value</replaceable> ]</literal></term>

        <listitem>
        <para>
        This command sets options affecting the output of query result
        tables. <replaceable class="parameter">parameter</replaceable>
        describes which option is to be set. The semantics of
        <replaceable class="parameter">value</replaceable> depend
        thereon.
        </para>

        <para>
        Adjustable printing options are:
        <variablelist>
          <varlistentry>
          <term><literal>format</literal></term>
          <listitem>
          <para>
          Sets the output format to one of <literal>unaligned</literal>,
          <literal>aligned</literal>, <literal>html</literal>,
          <literal>latex</literal>, or <literal>troff-ms</literal>.
          Unique abbreviations are allowed.  (That would mean one letter
          is enough.)
          </para>

          <para>
          <quote>Unaligned</quote> writes all columns of a row on a
          line, separated by the currently active field separator. This
          is intended to create output that might be intended to be read
          in by other programs (tab-separated, comma-separated).
          <quote>Aligned</quote> mode is the standard, human-readable,
          nicely formatted text output that is default. The
          <quote><acronym>HTML</acronym></quote> and
          <quote>LaTeX</quote> modes put out tables that are intended to
          be included in documents using the respective mark-up
          language. They are not complete documents! (This might not be
          so dramatic in <acronym>HTML</acronym>, but in LaTeX you must
          have a complete document wrapper.)
          </para>
          </listitem>
          </varlistentry>

          <varlistentry>
          <term><literal>border</literal></term>
          <listitem>
          <para>
          The second argument must be a number. In general, the higher
          the number the more borders and lines the tables will have,
          but this depends on the particular format. In
          <acronym>HTML</acronym> mode, this will translate directly
          into the <literal>border=...</literal> attribute, in the
          others only values 0 (no border), 1 (internal dividing lines),
          and 2 (table frame) make sense.
          </para>
          </listitem>
          </varlistentry>

          <varlistentry>
          <term><literal>expanded</literal> (or <literal>x</literal>)</term>
          <listitem>
          <para>
          You can specify an optional second argument, if it is provided it
          may be either <literal>on</literal> or <literal>off</literal>
          which will enable or disable expanded mode.  If the second
          argument is not provided then we will toggle between regular and
          expanded format. When expanded format is enabled, query results
          are displayed in two columns, with the column name on the left and
          the data on the right. This mode is useful if the data wouldn't fit
          on the screen in the normal <quote>horizontal</quote> mode.
          </para>

          <para>
          Expanded mode is supported by all four output formats.
          </para>
          </listitem>
          </varlistentry>

          <varlistentry>
          <term><literal>null</literal></term>
          <listitem>
          <para>
          The second argument is a string that should be printed
          whenever a column is null. The default is not to print
          anything, which can easily be mistaken for, say, an empty
          string. Thus, one might choose to write <literal>\pset null
          '(null)'</literal>.
          </para>
          </listitem>
          </varlistentry>

          <varlistentry>
          <term><literal>fieldsep</literal></term>
          <listitem>
          <para>
          Specifies the field separator to be used in unaligned output
          mode. That way one can create, for example, tab- or
          comma-separated output, which other programs might prefer. To
          set a tab as field separator, type <literal>\pset fieldsep
          '\t'</literal>. The default field separator is
          <literal>'|'</literal> (a vertical bar).
          </para>
          </listitem>
          </varlistentry>

          <varlistentry>
          <term><literal>footer</literal></term>
          <listitem>
          <para>
          You can specify an optional second argument, if it is provided it
          may be either <literal>on</literal> or <literal>off</literal>
          which will enable or disable display of the default footer
          <literal>(x rows)</literal>.  If the second argument is not
          provided then we will toggle between on and off.
          </para>
          </listitem>
          </varlistentry>

          <varlistentry>
          <term><literal>numericlocale</literal></term>
          <listitem>
          <para>
          You can specify an optional second argument, if it is provided it
          may be either <literal>on</literal> or <literal>off</literal>
          which will enable or disable display of a locale-aware character
          to seperate groups of digits to the left of the decimal marker.  If
          the second argument is not provided then we will toggle between
          on and off.
          </para>
          </listitem>
          </varlistentry>

          <varlistentry>
          <term><literal>recordsep</literal></term>
          <listitem>
          <para>
          Specifies the record (line) separator to use in unaligned
          output mode. The default is a newline character.
          </para>
          </listitem>
          </varlistentry>

          <varlistentry>
          <term><literal>tuples_only</literal> (or <literal>t</literal>)</term>
          <listitem>
          <para>
          You can specify an optional second argument, if it is provided it
          may be either <literal>on</literal> or <literal>off</literal>
          which will enable or disable the tuples only mode.  If the
          second argument is not provided then we will toggle between tuples
          only and full display. Full display shows extra information such
          as column headers, titles, and various footers. In tuples only
          mode, only actual table data is shown.
          </para>
          </listitem>
          </varlistentry>

          <varlistentry>
          <term><literal>title [ <replaceable class="parameter">text</replaceable> ]</literal></term>
          <listitem>
          <para>
          Sets the table title for any subsequently printed tables. This
          can be used to give your output descriptive tags. If no
          argument is given, the title is unset.
          </para>
          </listitem>
          </varlistentry>

          <varlistentry>
          <term><literal>tableattr</literal> (or <literal>T</literal>) <literal>[ <replaceable class="parameter">text</replaceable> ]</literal></term>
          <listitem>
          <para>
          Allows you to specify any attributes to be placed inside the
          <acronym>HTML</acronym> <sgmltag>table</sgmltag> tag. This
          could for example be <literal>cellpadding</literal> or
          <literal>bgcolor</literal>. Note that you probably don't want
          to specify <literal>border</literal> here, as that is already
          taken care of by <literal>\pset border</literal>.
          </para>
          </listitem>
          </varlistentry>


          <varlistentry>
          <term><literal>pager</literal></term>
          <listitem>
          <para>
          Controls use of a pager for query and <application>psql</>
          help output. If the environment variable <envar>PAGER</envar>
          is set, the output is piped to the specified program.
          Otherwise a platform-dependent default (such as
          <filename>more</filename>) is used.
          </para>

          <para>
          When the pager is off, the pager is not used. When the pager
          is on, the pager is used only when appropriate, i.e. the
          output is to a terminal and will not fit on the screen.
          (<application>psql</> does not do a perfect job of estimating
          when to use the pager.) <literal>\pset pager</> turns the
          pager on and off. Pager can also be set to <literal>always</>,
          which causes the pager to be always used, or you can set the pager
          to <literal>on</> which will enable the usage of the pager when
          appropriate, or you can set the pager to <literal>off</> which
          will disable the pager.
          </para>
          </listitem>
          </varlistentry>
        </variablelist>
        </para>

        <para>
        Illustrations on how these different formats look can be seen in
        the <xref linkend="APP-PSQL-examples"
        endterm="APP-PSQL-examples-title"> section.
        </para>

        <tip>
        <para>
        There are various shortcut commands for <command>\pset</command>. See
        <command>\a</command>, <command>\C</command>, <command>\H</command>,
        <command>\t</command>, <command>\T</command>, and <command>\x</command>.
        </para>
        </tip>

        <note>
        <para>
        It is an error to call <command>\pset</command> without
        arguments. In the future this call might show the current status
        of all printing options.
        </para>
        </note>

        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\q</literal></term>
        <listitem>
        <para>
        Quits the <application>psql</application> program.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\qecho <replaceable class="parameter">text</replaceable> [ ... ] </literal></term>
        <listitem>
        <para>
        This command is identical to <command>\echo</command> except
        that the output will be written to the query output channel, as
        set by <command>\o</command>.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\r</literal></term>
        <listitem>
        <para>
        Resets (clears) the query buffer.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\s [ <replaceable class="parameter">filename</replaceable> ]</literal></term>
        <listitem>
        <para>
        Print or save the command line history to <replaceable
        class="parameter">filename</replaceable>. If <replaceable
        class="parameter">filename</replaceable> is omitted, the history
        is written to the standard output. This option is only available
        if <application>psql</application> is configured to use the
        <acronym>GNU</acronym> <application>Readline</application> library.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\set [ <replaceable class="parameter">name</replaceable> [ <replaceable class="parameter">value</replaceable> [ ... ] ] ]</literal></term>

        <listitem>
        <para>
        Sets the internal variable <replaceable
        class="parameter">name</replaceable> to <replaceable
        class="parameter">value</replaceable> or, if more than one value
        is given, to the concatenation of all of them. If no second
        argument is given, the variable is just set with no value. To
        unset a variable, use the <command>\unset</command> command.
        </para>

        <para>
        Valid variable names can contain characters, digits, and
        underscores. See the section <xref
        linkend="APP-PSQL-variables"
        endterm="APP-PSQL-variables-title"> below for details.
        Variable names are case-sensitive.
        </para>

        <para>
        Although you are welcome to set any variable to anything you
        want, <application>psql</application> treats several variables
        as special. They are documented in the section about variables.
        </para>

        <note>
        <para>
        This command is totally separate from the <acronym>SQL</acronym>
        command <xref linkend="SQL-SET" endterm="SQL-SET-title">.
        </para>
        </note>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\t</literal></term>
        <listitem>
        <para>
        Toggles the display of output column name headings and row count
        footer. This command is equivalent to <literal>\pset
        tuples_only</literal> and is provided for convenience.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\T <replaceable class="parameter">table_options</replaceable></literal></term>
        <listitem>
        <para>
        Allows you to specify attributes to be placed within the
        <sgmltag>table</sgmltag> tag in <acronym>HTML</acronym> tabular
        output mode. This command is equivalent to <literal>\pset
        tableattr <replaceable
        class="parameter">table_options</replaceable></literal>.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
       <term><literal>\timing</literal></term>
        <listitem>
        <para>
         Toggles a display of how long each SQL statement takes, in milliseconds.
        </para>
       </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\w</literal> {<replaceable class="parameter">filename</replaceable> | <replaceable class="parameter">|command</replaceable>}</term>
        <listitem>
        <para>
        Outputs the current query buffer to the file <replaceable
        class="parameter">filename</replaceable> or pipes it to the Unix
        command <replaceable class="parameter">command</replaceable>.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\x</literal></term>
        <listitem>
        <para>
        Toggles expanded table formatting mode. As such it is equivalent to
        <literal>\pset expanded</literal>.
       </para>
       </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\z [ <replaceable class="parameter">pattern</replaceable> ]</literal></term>
        <listitem>
        <para>
        Produces a list of all available tables, views and sequences with their
        associated access privileges.
        If a <replaceable class="parameter">pattern</replaceable> is
        specified, only tables,views and sequences whose names match the pattern are listed.
        </para>

        <para>
        The <xref linkend="sql-grant" endterm="sql-grant-title"> and
        <xref linkend="sql-revoke" endterm="sql-revoke-title">
        commands are used to set access privileges.
        </para>

        <para>
        This is an alias for <command>\dp</command> (<quote>display
        privileges</quote>).
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\! [ <replaceable class="parameter">command</replaceable> ]</literal></term>
        <listitem>
        <para>
        Escapes to a separate Unix shell or executes the Unix command
        <replaceable class="parameter">command</replaceable>. The
        arguments are not further interpreted, the shell will see them
        as is.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\?</literal></term>
        <listitem>
        <para>
        Shows help information about the backslash commands.
        </para>
        </listitem>
      </varlistentry>

    </variablelist>
  </para>

  <refsect3 id="APP-PSQL-patterns">
   <title id="APP-PSQL-patterns-title">Patterns</title>

   <indexterm>
    <primary>patterns</primary>
    <secondary>in psql and pg_dump</secondary>
   </indexterm>

  <para>
   The various <literal>\d</> commands accept a <replaceable
   class="parameter">pattern</replaceable> parameter to specify the
   object name(s) to be displayed.  In the simplest case, a pattern
   is just the exact name of the object.  The characters within a
   pattern are normally folded to lower case, just as in SQL names;
   for example, <literal>\dt FOO</> will display the table named
   <literal>foo</>.  As in SQL names, placing double quotes around
   a pattern stops folding to lower case.  Should you need to include
   an actual double quote character in a pattern, write it as a pair
   of double quotes within a double-quote sequence; again this is in
   accord with the rules for SQL quoted identifiers.  For example,
   <literal>\dt "FOO""BAR"</> will display the table named
   <literal>FOO"BAR</> (not <literal>foo"bar</>).  Unlike the normal
   rules for SQL names, you can put double quotes around just part
   of a pattern, for instance <literal>\dt FOO"FOO"BAR</> will display
   the table named <literal>fooFOObar</>.
  </para>

  <para>
   Within a pattern, <literal>*</> matches any sequence of characters
   (including no characters) and <literal>?</> matches any single character.
   (This notation is comparable to Unix shell file name patterns.)
   For example, <literal>\dt int*</> displays all tables whose names
   begin with <literal>int</>.  But within double quotes, <literal>*</>
   and <literal>?</> lose these special meanings and are just matched
   literally.
  </para>

  <para>
   A pattern that contains a dot (<literal>.</>) is interpreted as a schema
   name pattern followed by an object name pattern.  For example,
   <literal>\dt foo*.*bar*</> displays all tables whose table name
   includes <literal>bar</> that are in schemas whose schema name
   starts with <literal>foo</>.  When no dot appears, then the pattern
   matches only objects that are visible in the current schema search path.
   Again, a dot within double quotes loses its special meaning and is matched
   literally.
  </para>

  <para>
   Advanced users can use regular-expression notations such as character
   classes, for example <literal>[0-9]</> to match any digit.  All regular
   expression special characters work as specified in
   <xref linkend="functions-posix-regexp">, except for <literal>.</> which
   is taken as a separator as mentioned above, <literal>*</> which is
   translated to the regular-expression notation <literal>.*</>,
   <literal>?</> which is translated to <literal>.</>, and
   <literal>$</> which is matched literally.  You can emulate
   these pattern characters at need by writing
   <literal>?</> for <literal>.</>,
   <literal>(<replaceable class="parameter">R</replaceable>+|)</literal> for
   <literal><replaceable class="parameter">R</replaceable>*</literal>, or
   <literal>(<replaceable class="parameter">R</replaceable>|)</literal> for
   <literal><replaceable class="parameter">R</replaceable>?</literal>.
   <literal>$</> is not needed as a regular-expression character since
   the pattern must match the whole name, unlike the usual
   interpretation of regular expressions (in other words, <literal>$</>
   is automatically appended to your pattern).  Write <literal>*</> at the
   beginning and/or end if you don't wish the pattern to be anchored.
   Note that within double quotes, all regular expression special characters
   lose their special meanings and are matched literally.  Also, the regular
   expression special characters are matched literally in operator name
   patterns (i.e., the argument of <literal>\do</>).
  </para>

  <para>
   Whenever the <replaceable class="parameter">pattern</replaceable> parameter
   is omitted completely, the <literal>\d</> commands display all objects
   that are visible in the current schema search path &mdash; this is
   equivalent to using the pattern <literal>*</>.
   To see all objects in the database, use the pattern <literal>*.*</>.
  </para>
  </refsect3>
 </refsect2>

 <refsect2>
  <title>Advanced features</title>

   <refsect3 id="APP-PSQL-variables">
    <title id="APP-PSQL-variables-title">Variables</title>

    <para>
    <application>psql</application> provides variable substitution
    features similar to common Unix command shells.
    Variables are simply name/value pairs, where the value
    can be any string of any length. To set variables, use the
    <application>psql</application> meta-command
    <command>\set</command>:
<programlisting>
testdb=&gt; <userinput>\set foo bar</userinput>
</programlisting>
    sets the variable <literal>foo</literal> to the value
    <literal>bar</literal>. To retrieve the content of the variable, precede
    the name with a colon and use it as the argument of any slash
    command:
<programlisting>
testdb=&gt; <userinput>\echo :foo</userinput>
bar
</programlisting>
    </para>

    <note>
    <para>
    The arguments of <command>\set</command> are subject to the same
    substitution rules as with other commands. Thus you can construct
    interesting references such as <literal>\set :foo
    'something'</literal> and get <quote>soft links</quote> or
    <quote>variable variables</quote> of <productname>Perl</productname>
    or <productname><acronym>PHP</acronym></productname> fame,
    respectively. Unfortunately (or fortunately?), there is no way to do
    anything useful with these constructs. On the other hand,
    <literal>\set bar :foo</literal> is a perfectly valid way to copy a
    variable.
    </para>
    </note>

    <para>
    If you call <command>\set</command> without a second argument, the
    variable is set, with an empty string as value. To unset (or delete) a
    variable, use the command <command>\unset</command>.
    </para>

    <para>
    <application>psql</application>'s internal variable names can
    consist of letters, numbers, and underscores in any order and any
    number of them. A number of these variables are treated specially
    by <application>psql</application>. They indicate certain option
    settings that can be changed at run time by altering the value of
    the variable or represent some state of the application. Although
    you can use these variables for any other purpose, this is not
    recommended, as the program behavior might grow really strange
    really quickly. By convention, all specially treated variables
    consist of all upper-case letters (and possibly numbers and
    underscores). To ensure maximum compatibility in the future, avoid
    using such variable names for your own purposes. A list of all specially
    treated variables follows.
   </para>

    <variablelist>
      <varlistentry>
      <indexterm>
       <primary>autocommit</primary>
       <secondary>psql</secondary>
      </indexterm>
        <term><varname>AUTOCOMMIT</varname></term>
        <listitem>
        <para>
        When <literal>on</> (the default), each SQL command is automatically
        committed upon successful completion.  To postpone commit in this
        mode, you must enter a <command>BEGIN</> or <command>START
        TRANSACTION</> SQL command.  When <literal>off</> or unset, SQL
        commands are not committed until you explicitly issue
        <command>COMMIT</> or <command>END</>.  The autocommit-off
        mode works by issuing an implicit <command>BEGIN</> for you, just
        before any command that is not already in a transaction block and
        is not itself a <command>BEGIN</> or other transaction-control
        command, nor a command that cannot be executed inside a transaction
        block (such as <command>VACUUM</>).
        </para>

        <note>
        <para>
         In autocommit-off mode, you must explicitly abandon any failed
         transaction by entering <command>ABORT</> or <command>ROLLBACK</>.
         Also keep in mind that if you exit the session
         without committing, your work will be lost.
        </para>
        </note>

        <note>
        <para>
         The autocommit-on mode is <productname>PostgreSQL</>'s traditional
         behavior, but autocommit-off is closer to the SQL spec.  If you
         prefer autocommit-off, you might wish to set it in the system-wide
         <filename>psqlrc</filename> file or your
         <filename>~/.psqlrc</filename> file.
        </para>
        </note>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>DBNAME</varname></term>
        <listitem>
        <para>
        The name of the database you are currently connected to. This is
        set every time you connect to a database (including program
        start-up), but can be unset.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ECHO</varname></term>
        <listitem>
        <para>
        If set to <literal>all</literal>, all lines
        entered from the keyboard or from a script are written to the standard output
        before they are parsed or executed. To select this behavior on program
        start-up, use the switch <option>-a</option>. If set to
        <literal>queries</literal>,
        <application>psql</application> merely prints all queries as
        they are sent to the server. The switch for this is
        <option>-e</option>.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ECHO_HIDDEN</varname></term>
        <listitem>
        <para>
        When this variable is set and a backslash command queries the
        database, the query is first shown. This way you can study the
        <productname>PostgreSQL</productname> internals and provide
        similar functionality in your own programs. (To select this behavior
        on program start-up, use the switch <option>-E</option>.)  If you set
        the variable to the value <literal>noexec</literal>, the queries are
        just shown but are not actually sent to the server and executed.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ENCODING</varname></term>
        <listitem>
        <para>
        The current client character set encoding.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>FETCH_COUNT</varname></term>
        <listitem>
        <para>
        If this variable is set to an integer value &gt; 0,
        the results of <command>SELECT</command> queries are fetched
        and displayed in groups of that many rows, rather than the
        default behavior of collecting the entire result set before
        display.  Therefore only a
        limited amount of memory is used, regardless of the size of
        the result set.  Settings of 100 to 1000 are commonly used
        when enabling this feature.
        Keep in mind that when using this feature, a query might
        fail after having already displayed some rows.
        </para>
        <tip>
        <para>
        Although you can use any output format with this feature,
        the default <literal>aligned</> format tends to look bad
        because each group of <varname>FETCH_COUNT</varname> rows
        will be formatted separately, leading to varying column
        widths across the row groups.  The other output formats work better.
        </para>
        </tip>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>HISTCONTROL</varname></term>
        <listitem>
        <para>
         If this variable is set to <literal>ignorespace</literal>,
         lines which begin with a space are not entered into the history
         list. If set to a value of <literal>ignoredups</literal>, lines
         matching the previous history line are not entered. A value of
         <literal>ignoreboth</literal> combines the two options. If
         unset, or if set to any other value than those above, all lines
         read in interactive mode are saved on the history list.
        </para>
        <note>
        <para>
        This feature was shamelessly plagiarized from
        <application>Bash</application>.
        </para>
        </note>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>HISTFILE</varname></term>
        <listitem>
        <para>
        The file name that will be used to store the history list. The default
        value is <filename>~/.psql_history</filename>.  For example, putting:
<programlisting>
\set HISTFILE ~/.psql_history- :DBNAME
</programlisting>
        in <filename>~/.psqlrc</filename> will cause
        <application>psql</application> to maintain a separate history for
        each database.
        </para>
        <note>
        <para>
        This feature was shamelessly plagiarized from
        <application>Bash</application>.
        </para>
        </note>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>HISTSIZE</varname></term>
        <listitem>
        <para>
        The number of commands to store in the command history. The
        default value is 500.
        </para>
        <note>
        <para>
        This feature was shamelessly plagiarized from
        <application>Bash</application>.
        </para>
        </note>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>HOST</varname></term>
        <listitem>
        <para>
        The database server host you are currently connected to. This is
        set every time you connect to a database (including program
        start-up), but can be unset.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>IGNOREEOF</varname></term>
        <listitem>
        <para>
         If unset, sending an <acronym>EOF</> character (usually
         <keycombo action="simul"><keycap>Control</><keycap>D</></>)
         to an interactive session of <application>psql</application>
         will terminate the application. If set to a numeric value,
         that many <acronym>EOF</> characters are ignored before the
         application terminates.  If the variable is set but has no
         numeric value, the default is 10.
        </para>
        <note>
        <para>
        This feature was shamelessly plagiarized from
        <application>Bash</application>.
        </para>
        </note>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>LASTOID</varname></term>
        <listitem>
        <para>
        The value of the last affected OID, as returned from an
        <command>INSERT</command> or <command>lo_insert</command>
        command. This variable is only guaranteed to be valid until
        after the result of the next <acronym>SQL</acronym> command has
        been displayed.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
      <indexterm>
       <primary>rollback</primary>
       <secondary>psql</secondary>
      </indexterm>
        <term><varname>ON_ERROR_ROLLBACK</varname></term>
        <listitem>
        <para>
        When <literal>on</>, if a statement in a transaction block
        generates an error, the error is ignored and the transaction
        continues. When <literal>interactive</>, such errors are only
        ignored in interactive sessions, and not when reading script
        files. When <literal>off</> (the default), a statement in a
        transaction block that generates an error aborts the entire
        transaction. The on_error_rollback-on mode works by issuing an
        implicit <command>SAVEPOINT</> for you, just before each command
        that is in a transaction block, and rolls back to the savepoint
        on error.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ON_ERROR_STOP</varname></term>
        <listitem>
        <para>
        By default, if non-interactive scripts encounter an error, such
        as a malformed <acronym>SQL</acronym> command or internal
        meta-command, processing continues. This has been the
        traditional behavior of <application>psql</application> but it
        is sometimes not desirable. If this variable is set, script
        processing will immediately terminate. If the script was called
        from another script it will terminate in the same fashion. If
        the outermost script was not called from an interactive
        <application>psql</application> session but rather using the
        <option>-f</option> option, <application>psql</application> will
        return error code 3, to distinguish this case from fatal error
        conditions (error code 1).
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>PORT</varname></term>
        <listitem>
        <para>
        The database server port to which you are currently connected.
        This is set every time you connect to a database (including
        program start-up), but can be unset.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>PROMPT1</varname></term>
        <term><varname>PROMPT2</varname></term>
        <term><varname>PROMPT3</varname></term>
        <listitem>
        <para>
        These specify what the prompts <application>psql</application>
        issues should look like. See <xref
        linkend="APP-PSQL-prompting"
        endterm="APP-PSQL-prompting-title"> below.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>QUIET</varname></term>
        <listitem>
        <para>
        This variable is equivalent to the command line option
        <option>-q</option>. It is probably not too useful in
        interactive mode.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SINGLELINE</varname></term>
        <listitem>
        <para>
        This variable is equivalent to the command line option
        <option>-S</option>.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>SINGLESTEP</varname></term>
        <listitem>
        <para>
        This variable is equivalent to the command line option
        <option>-s</option>.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>USER</varname></term>
        <listitem>
        <para>
        The database user you are currently connected as. This is set
        every time you connect to a database (including program
        start-up), but can be unset.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>VERBOSITY</varname></term>
        <listitem>
        <para>
        This variable can be set to the values <literal>default</>,
        <literal>verbose</>, or <literal>terse</> to control the verbosity
        of error reports.
        </para>
        </listitem>
      </varlistentry>

    </variablelist>

   </refsect3>

   <refsect3>
    <title><acronym>SQL</acronym> Interpolation</title>

    <para>
    An additional useful feature of <application>psql</application>
    variables is that you can substitute (<quote>interpolate</quote>)
    them into regular <acronym>SQL</acronym> statements. The syntax for
    this is again to prepend the variable name with a colon
    (<literal>:</literal>):
<programlisting>
testdb=&gt; <userinput>\set foo 'my_table'</userinput>
testdb=&gt; <userinput>SELECT * FROM :foo;</userinput>
</programlisting>
    would then query the table <literal>my_table</literal>. The value of
    the variable is copied literally, so it can even contain unbalanced
    quotes or backslash commands. You must make sure that it makes sense
    where you put it. Variable interpolation will not be performed into
    quoted <acronym>SQL</acronym> entities.
    </para>

    <para>
    A popular application of this facility is to refer to the last
    inserted <acronym>OID</acronym> in subsequent statements to build a
    foreign key scenario. Another possible use of this mechanism is to
    copy the contents of a file into a table column. First load the file into a
    variable and then proceed as above:
<programlisting>
testdb=&gt; <userinput>\set content '''' `cat my_file.txt` ''''</userinput>
testdb=&gt; <userinput>INSERT INTO my_table VALUES (:content);</userinput>
</programlisting>
    One problem with this approach is that <filename>my_file.txt</filename>
    might contain single quotes. These need to be escaped so that
    they don't cause a syntax error when the second line is processed. This
    could be done with the program <command>sed</command>:
<programlisting>
testdb=&gt; <userinput>\set content '''' `sed -e "s/'/''/g" &lt; my_file.txt` ''''</userinput>
</programlisting>
    If you are using non-standard-conforming strings then you'll also need
    to double backslashes.  This is a bit tricky:
<programlisting>
testdb=&gt; <userinput>\set content '''' `sed -e "s/'/''/g" -e 's/\\/\\\\/g' &lt; my_file.txt` ''''</userinput>
</programlisting>
    Note the use of different shell quoting conventions so that neither
    the single quote marks nor the backslashes are special to the shell.
    Backslashes are still special to <command>sed</command>, however, so
    we need to double them.  (Perhaps
    at one point you thought it was great that all Unix commands use the
    same escape character.)
    </para>

    <para>
    Since colons can legally appear in SQL commands, the following rule
    applies: the character sequence
    <quote>:name</quote> is not changed unless <quote>name</> is the name
    of a variable that is currently set. In any case you can escape
    a colon with a backslash to protect it from substitution. (The
    colon syntax for variables is standard <acronym>SQL</acronym> for
    embedded query languages, such as <application>ECPG</application>.
    The colon syntax for array slices and type casts are
    <productname>PostgreSQL</productname> extensions, hence the
    conflict.)
    </para>

   </refsect3>

   <refsect3 id="APP-PSQL-prompting">
    <title id="APP-PSQL-prompting-title">Prompting</title>

    <para>
    The prompts <application>psql</application> issues can be customized
    to your preference. The three variables <varname>PROMPT1</varname>,
    <varname>PROMPT2</varname>, and <varname>PROMPT3</varname> contain strings
    and special escape sequences that describe the appearance of the
    prompt. Prompt 1 is the normal prompt that is issued when
    <application>psql</application> requests a new command. Prompt 2 is
    issued when more input is expected during command input because the
    command was not terminated with a semicolon or a quote was not closed.
    Prompt 3 is issued when you run an <acronym>SQL</acronym>
    <command>COPY</command> command and you are expected to type in the
    row values on the terminal.
    </para>

    <para>
    The value of the selected prompt variable is printed literally,
    except where a percent sign (<literal>%</literal>) is encountered.
    Depending on the next character, certain other text is substituted
    instead. Defined substitutions are:

    <variablelist>
      <varlistentry>
        <term><literal>%M</literal></term>
        <listitem>
         <para>
          The full host name (with domain name) of the database server,
          or <literal>[local]</literal> if the connection is over a Unix
          domain socket, or
          <literal>[local:<replaceable>/dir/name</replaceable>]</literal>, 
          if the Unix domain socket is not at the compiled in default
          location.
        </para>
       </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%m</literal></term>
        <listitem>
         <para>
          The host name of the database server, truncated at the
          first dot, or <literal>[local]</literal> if the connection is
          over a Unix domain socket.
         </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%&gt;</literal></term>
        <listitem><para>The port number at which the database server is listening.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%n</literal></term>
        <listitem>
         <para>
          The database session user name.  (The expansion of this
          value might change during a database session as the result
          of the command <command>SET SESSION
          AUTHORIZATION</command>.)
         </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%/</literal></term>
        <listitem><para>The name of the current database.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%~</literal></term>
        <listitem><para>Like <literal>%/</literal>, but the output is <literal>~</literal>
         (tilde) if the database is your default database.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%#</literal></term>
        <listitem>
         <para>
          If the session user is a database superuser, then a
          <literal>#</literal>, otherwise a <literal>&gt;</literal>.
          (The expansion of this value might change during a database
          session as the result of the command <command>SET SESSION
          AUTHORIZATION</command>.)
         </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%R</literal></term>
        <listitem>
        <para>
        In prompt 1 normally <literal>=</literal>, but <literal>^</literal> if
        in single-line mode, and <literal>!</literal> if the session is
        disconnected from the database (which can happen if
        <command>\connect</command> fails). In prompt 2 the sequence is
        replaced by <literal>-</literal>, <literal>*</literal>, a single quote,
        a double quote, or a dollar sign, depending on whether
        <application>psql</application> expects more input because the
        command wasn't terminated yet, because you are inside a
        <literal>/* ... */</literal> comment, or because you are inside
        a quoted or dollar-escaped string. In prompt 3 the sequence doesn't
        produce anything.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%x</literal></term>
        <listitem>
        <para>
        Transaction status: an empty string when not in a transaction
        block, or <literal>*</> when in a transaction block, or
        <literal>!</> when in a failed transaction block, or <literal>?</>
        when the transaction state is indeterminate (for example, because
        there is no connection).
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%</literal><replaceable class="parameter">digits</replaceable></term>
        <listitem>
        <para>
        The character with the indicated octal code is substituted.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%:</literal><replaceable class="parameter">name</replaceable><literal>:</literal></term>
        <listitem>
        <para>
        The value of the <application>psql</application> variable
        <replaceable class="parameter">name</replaceable>. See the
        section <xref linkend="APP-PSQL-variables"
        endterm="APP-PSQL-variables-title"> for details.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%`</literal><replaceable class="parameter">command</replaceable><literal>`</literal></term>
        <listitem>
        <para>
        The output of <replaceable
        class="parameter">command</replaceable>, similar to ordinary
        <quote>back-tick</quote> substitution.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%[</literal> ... <literal>%]</literal></term>
        <listitem>
         <para>
         Prompts can contain terminal control characters which, for
         example, change the color, background, or style of the prompt
         text, or change the title of the terminal window. In order for
         the line editing features of <application>Readline</application> to work properly, these
         non-printing control characters must be designated as invisible
         by surrounding them with <literal>%[</literal> and
         <literal>%]</literal>. Multiple pairs of these can occur within
         the prompt.  For example:
<programlisting>
testdb=&gt; \set PROMPT1 '%[%033[1;33;40m%]%n@%/%R%[%033[0m%]%# '
</programlisting>
         results in a boldfaced (<literal>1;</literal>) yellow-on-black
         (<literal>33;40</literal>) prompt on VT100-compatible, color-capable
         terminals.
        </para>
        </listitem>
      </varlistentry>

    </variablelist>

    To insert a percent sign into your prompt, write
    <literal>%%</literal>. The default prompts are
    <literal>'%/%R%# '</literal> for prompts 1 and 2, and
    <literal>'&gt;&gt; '</literal> for prompt 3.
    </para>

    <note>
    <para>
    This feature was shamelessly plagiarized from
    <application>tcsh</application>.
    </para>
    </note>

   </refsect3>

   <refsect3>
    <title>Command-Line Editing</title>

    <para>
    <application>psql</application> supports the <application>Readline</application>
    library for convenient line editing and retrieval. The command
    history is automatically saved when <application>psql</application>
    exits and is reloaded when
    <application>psql</application> starts up. Tab-completion is also
    supported, although the completion logic makes no claim to be an
    <acronym>SQL</acronym> parser.  If for some reason you do not like the tab completion, you
    can turn it off by putting this in a file named
    <filename>.inputrc</filename> in your home directory:
<programlisting>
$if psql
set disable-completion on
$endif
</programlisting>
    (This is not a <application>psql</application> but a
    <application>Readline</application> feature. Read its documentation
    for further details.)
    </para>
   </refsect3>
  </refsect2>
 </refsect1>


 <refsect1>
  <title>Environment</title>

  <variablelist>
   <varlistentry>
    <term><envar>PAGER</envar></term>

    <listitem>
     <para>
      If the query results do not fit on the screen, they are piped
      through this command.  Typical values are
      <literal>more</literal> or <literal>less</literal>.  The default
      is platform-dependent.  The use of the pager can be disabled by
      using the <command>\pset</command> command.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><envar>PGDATABASE</envar></term>

    <listitem>
     <para>
      Default connection database
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><envar>PGHOST</envar></term>
    <term><envar>PGPORT</envar></term>
    <term><envar>PGUSER</envar></term>

    <listitem>
     <para>
      Default connection parameters
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><envar>PSQL_EDITOR</envar></term>
    <term><envar>EDITOR</envar></term>
    <term><envar>VISUAL</envar></term>

    <listitem>
     <para>
      Editor used by the <command>\e</command> command.  The variables
      are examined in the order listed; the first that is set is used.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><envar>SHELL</envar></term>

    <listitem>
     <para>
      Command executed by the <command>\!</command> command.
     </para>
    </listitem>
   </varlistentry>

   <varlistentry>
    <term><envar>TMPDIR</envar></term>

    <listitem>
     <para>
      Directory for storing temporary files.  The default is
      <filename>/tmp</filename>.
     </para>
    </listitem>
   </varlistentry>
  </variablelist>

  <para>
   This utility, like most other <productname>PostgreSQL</> utilities,
   also uses the environment variables supported by <application>libpq</>
   (see <xref linkend="libpq-envars">).
  </para>

 </refsect1>


 <refsect1>
  <title>Files</title>

  <itemizedlist>
   <listitem>
    <para>
     Before starting up, <application>psql</application> attempts to
     read and execute commands from the system-wide
     <filename>psqlrc</filename> file and the user's
     <filename>~/.psqlrc</filename> file.
     (On Windows, the user's startup file is named
     <filename>%APPDATA%\postgresql\psqlrc.conf</filename>.)
     See <filename><replaceable>PREFIX</>/share/psqlrc.sample</>
     for information on setting up the system-wide file.  It could be used
     to set up the client or the server to taste (using the <command>\set
     </command> and <command>SET</command> commands).
    </para>
   </listitem>

   <listitem>
    <para>
     Both the system-wide <filename>psqlrc</filename> file and the user's
     <filename>~/.psqlrc</filename> file can be made version-specific
     by appending a dash and the <productname>PostgreSQL</productname>
     release number, for example <filename>~/.psqlrc-&version;</filename>.
     A matching version-specific file will be read in preference to a
     non-version-specific file.
    </para>
   </listitem>

   <listitem>
    <para>
     The command-line history is stored in the file
     <filename>~/.psql_history</filename>, or
     <filename>%APPDATA%\postgresql\psql_history</filename> on Windows.
    </para>
   </listitem>
  </itemizedlist>
 </refsect1>


 <refsect1>
  <title>Notes</title>

    <itemizedlist>
      <listitem>
      <para>
      In an earlier life <application>psql</application> allowed the
      first argument of a single-letter backslash command to start
      directly after the command, without intervening whitespace. For
      compatibility this is still supported to some extent,
      but we are not going to explain the details here as this use is
      discouraged.  If you get strange messages, keep this in mind.
      For example:
<programlisting>
testdb=&gt; <userinput>\foo</userinput>
Field separator is "oo".
</programlisting>
      which is perhaps not what one would expect.
      </para>
      </listitem>

      <listitem>
      <para>
      <application>psql</application> only works smoothly with servers
      of the same version. That does not mean other combinations will
      fail outright, but subtle and not-so-subtle problems might come
      up.  Backslash commands are particularly likely to fail if the
      server is of a different version.
      </para>
      </listitem>

    </itemizedlist>
 </refsect1>


 <refsect1>
  <title>Notes for Windows users</title>

 <para>
  <application>psql</application> is built as a <quote>console
  application</>.  Since the Windows console windows use a different
  encoding than the rest of the system, you must take special care
  when using 8-bit characters within <application>psql</application>.
  If <application>psql</application> detects a problematic
  console code page, it will warn you at startup. To change the
  console code page, two things are necessary:

   <itemizedlist>
    <listitem>
     <para>
      Set the code page by entering <userinput>cmd.exe /c chcp
      1252</userinput>. (1252 is a code page that is appropriate for
      German; replace it with your value.) If you are using Cygwin,
      you can put this command in <filename>/etc/profile</filename>.
     </para>
    </listitem>

    <listitem>
     <para>
      Set the console font to <literal>Lucida Console</>, because the
      raster font does not work with the ANSI code page.
     </para>
    </listitem>
   </itemizedlist>
 </para>

 </refsect1>


 <refsect1 id="APP-PSQL-examples">
  <title id="APP-PSQL-examples-title">Examples</title>

  <para>
  The first example shows how to spread a command over several lines of
  input. Notice the changing prompt:
<programlisting>
testdb=&gt; <userinput>CREATE TABLE my_table (</userinput>
testdb(&gt; <userinput> first integer not null default 0,</userinput>
testdb(&gt; <userinput> second text)</userinput>
testdb-&gt; <userinput>;</userinput>
CREATE TABLE
</programlisting>
  Now look at the table definition again:
<programlisting>
testdb=&gt; <userinput>\d my_table</userinput>
             Table "my_table"
 Attribute |  Type   |      Modifier
-----------+---------+--------------------
 first     | integer | not null default 0
 second    | text    |

</programlisting>
  Now we change the prompt to something more interesting:
<programlisting>
testdb=&gt; <userinput>\set PROMPT1 '%n@%m %~%R%# '</userinput>
peter@localhost testdb=&gt;
</programlisting>
  Let's assume you have filled the table with data and want to take a
  look at it:
<programlisting>
peter@localhost testdb=&gt; SELECT * FROM my_table;
 first | second
-------+--------
     1 | one
     2 | two
     3 | three
     4 | four
(4 rows)

</programlisting>
  You can display tables in different ways by using the
  <command>\pset</command> command:
<programlisting>
peter@localhost testdb=&gt; <userinput>\pset border 2</userinput>
Border style is 2.
peter@localhost testdb=&gt; <userinput>SELECT * FROM my_table;</userinput>
+-------+--------+
| first | second |
+-------+--------+
|     1 | one    |
|     2 | two    |
|     3 | three  |
|     4 | four   |
+-------+--------+
(4 rows)

peter@localhost testdb=&gt; <userinput>\pset border 0</userinput>
Border style is 0.
peter@localhost testdb=&gt; <userinput>SELECT * FROM my_table;</userinput>
first second
----- ------
    1 one
    2 two
    3 three
    4 four
(4 rows)

peter@localhost testdb=&gt; <userinput>\pset border 1</userinput>
Border style is 1.
peter@localhost testdb=&gt; <userinput>\pset format unaligned</userinput>
Output format is unaligned.
peter@localhost testdb=&gt; <userinput>\pset fieldsep ","</userinput>
Field separator is ",".
peter@localhost testdb=&gt; <userinput>\pset tuples_only</userinput>
Showing only tuples.
peter@localhost testdb=&gt; <userinput>SELECT second, first FROM my_table;</userinput>
one,1
two,2
three,3
four,4
</programlisting>
  Alternatively, use the short commands:
<programlisting>
peter@localhost testdb=&gt; <userinput>\a \t \x</userinput>
Output format is aligned.
Tuples only is off.
Expanded display is on.
peter@localhost testdb=&gt; <userinput>SELECT * FROM my_table;</userinput>
-[ RECORD 1 ]-
first  | 1
second | one
-[ RECORD 2 ]-
first  | 2
second | two
-[ RECORD 3 ]-
first  | 3
second | three
-[ RECORD 4 ]-
first  | 4
second | four
</programlisting>
  </para>

 </refsect1>

</refentry>
