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$Header: /cvsroot/pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.81 2002/12/12 21:02:19 momjian 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>

 <refsynopsisdiv>
  <cmdsynopsis>
   <command>psql</command>
   <arg><replaceable class="parameter">options</replaceable></arg>
   <arg><replaceable class="parameter">dbname</replaceable>
   <arg><replaceable class="parameter">user</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 the lines to the screen 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">query</replaceable></></term>
      <term><option>--command <replaceable class="parameter">query</replaceable></></term>
      <listitem>
      <para>
      Specifies that <application>psql</application> is to execute one
      query string, <replaceable class="parameter">query</replaceable>,
      and then exit. This is useful in shell scripts.
      </para>
      <para>
      <replaceable class="parameter">query</replaceable> must be either
      a query string that is completely parsable by the backend (i.e.,
      it contains no <application>psql</application> specific features),
      or it is a single backslash command. Thus you cannot mix
      <acronym>SQL</acronym> and <application>psql</application>
      meta-commands. To achieve that, you could pipe the string into
      <application>psql</application>, like this: <literal>echo "\x \\
      select * from foo;" | psql</literal>.
      </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>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-e</></term>
      <term><option>--echo-queries</></term>
      <listitem>
      <para>
      Show all queries that are sent to the backend. 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>
      Echoes the actual queries generated by \d and other backslash
      commands. You can use this if you wish to include similar
      functionality into your own programs. 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 queries instead of reading queries 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. 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
      <application>postmaster</application> is running. If host 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>
      Turns 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>
      Lists all available databases, then exits. Other non-connection
      options are ignored. This is similar to the internal command
      <command>\list</command>.
      </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/IP port or, by omission, the local Unix domain
      socket file extension on which the
      <application>postmaster</application> 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. 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 query is sent to the backend, 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 a query, 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. It is completely equivalent to the <command>\t</command>
      meta-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</></term>
      <listitem>
      <para>
      Makes <application>psql</application> prompt for the user name and
      password before connecting to the database.
      </para>

      <para>
      This option is deprecated, as it is conceptually flawed.
      (Prompting for a non-default user name and prompting for a
      password because the backend requires it are really two different
      things.) You are encouraged to look at the <option>-U</option> and
      <option>-W</option> options instead.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-U <replaceable class="parameter">username</replaceable></></term>
      <term><option>--username <replaceable class="parameter">username</replaceable></></term>
      <listitem>
      <para>
      Connects 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>
      Performs 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>
      Shows the <application>psql</application> version.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-W</></term>
      <term><option>--password</></term>
      <listitem>
      <para>
      Requests that <application>psql</application> should prompt for a
      password before connecting to a database. This will remain set for
      the entire session, even if you change the database connection
      with the meta-command <command>\connect</command>.
      </para>

      <para>
      In the current version, <application>psql</application>
      automatically issues a password prompt whenever the backend
      requests password authentication. Because this is currently based
      on a hack, the automatic recognition might mysteriously fail,
      hence this option to force a prompt. If no password prompt is
      issued and the backend requires password authentication the
      connection attempt will fail.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-x</></term>
      <term><option>--expanded</></term>
      <listitem>
      <para>
      Turns on extended row format mode. This is equivalent to the
      command <command>\x</command>.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-X,</></term>
      <term><option>--no-psqlrc</></term>
      <listitem>
      <para>
      Do not read the start-up file <filename>~/.psqlrc</filename>.
      </para>
      </listitem>
    </varlistentry>

    <varlistentry>
      <term><option>-?</></term>
      <term><option>--help</></term>
      <listitem>
      <para>
      Shows help about <application>psql</application> command line
      arguments.
      </para>
      </listitem>
    </varlistentry>
  </variablelist>

  <para>
   Long options are not available on all platforms.
  </para>
 </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 backend went bad
   and the session is 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 also given). Not all
    these options are required, defaults do apply. If you omit the host
    name, <application>psql</> will connect via a Unix domain socket to a server on the
    local host. The default port number is compile-time determined.
    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 can't
    just connect to any database under any user name. Your database
    administrator should have informed you about your access rights. To
    save you some typing you can also set the environment variables
    <envar>PGDATABASE</envar>, <envar>PGHOST</envar>,
    <envar>PGPORT</envar> and <envar>PGUSER</envar> to appropriate
    values.
    </para>

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

  <refsect2 id="R2-APP-PSQL-4">
    <title>Entering Queries</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 on internal slash commands
       \g or terminate with semicolon to execute query
       \q to quit

testdb=>
</programlisting>
    </para>

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

    <para>
    Whenever a query 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 are what makes
    <application>psql</application> interesting 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 may quote it with a
    single quote. To include a single quote into such an argument,
    precede it by a backslash. 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>,
    <literal>\0</literal><replaceable>digits</replaceable>, and
    <literal>\0x</literal><replaceable>digits</replaceable> (the
    character with the given decimal, octal, or hexadecimal code).
    </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> regarding double quotes: an
    identifier without double quotes is coerced to lower-case, while
    whitespace within double quotes is included in the argument.
    </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> queries, 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, switch to aligned.
	If it is not unaligned, set it to unaligned. This command is
	kept for backwards compatibility. See <command>\pset</command> for a
	general solution.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
       <term><literal>\cd</literal> <optional><replaceable>directory</replaceable></optional></term>
       <listitem>
        <para>
	 Change the current working directory to
	 <replaceable>directory</replaceable>. Without argument, change
	 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</literal> [ <replaceable class="parameter">title</replaceable> ]</term>
        <listitem>
        <para>
        Set 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>) [ <replaceable class="parameter">dbname</replaceable> [ <replaceable class="parameter">username</replaceable> ] ]</term>
        <listitem>
        <para>
	Establishes a connection to a new database and/or under a user
	name. The previous connection is closed. If <replaceable
	class="parameter">dbname</replaceable> is <literal>-</literal>
	the current database name is assumed.
	</para>

	<para>
	If <replaceable class="parameter">username</replaceable> is
	omitted the current user name is assumed. </para>

	<para>
	As a special rule, <command>\connect</command> without any
	arguments will connect to the default database as the default
	user (as you would have gotten by starting
	<application>psql</application> without any arguments).
	</para>

	<para>
	If the connection attempt failed (wrong user name, access
	denied, etc.), the previous connection will be kept if and only
	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> ) ]
        { <literal>from</literal> | <literal>to</literal> }
	<replaceable class="parameter">filename</replaceable> | stdin | stdout
        [ <literal>with</literal> ] 
            [ <literal>oids</literal> ] 
            [ <literal>delimiter [as] </literal> '<replaceable class="parameter">character</replaceable>' ]
            [ <literal>null [as] </literal> '<replaceable class="parameter">string</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 backend's
        reading or writing the specified file,
        <application>psql</application> reads or writes the file and
        routes the data between the backend 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> <command>COPY</command> command (see its
	description for the details). 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>

        <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 IP or socket connection. For large
	amounts of data the other technique may be preferable.
        </para>
        </tip>

        <note>
        <para>
        Note the difference in interpretation of
        <literal>stdin</literal> and <literal>stdout</literal> between
        frontend and backend copies: in a frontend copy these always
        refer to <application>psql</application>'s input and output
        stream. On a backend copy <literal>stdin</literal> comes from
        wherever the <command>COPY</command> itself came from (for
        example, a script run with the <option>-f</option> option), and
        <literal>stdout</literal> refers to the query output stream (see
        <command>\o</command> meta-command below).
        </para>
        </note>
        </listitem>
      </varlistentry>

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

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

        <listitem>
        <para>
	For each relation (table, view, index, or sequence) matching the
	<replaceable class="parameter">pattern</replaceable>, show all
	columns, their types, 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, but any
	comments associated with the table columns are shown as well.
	</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</literal> [ <replaceable class="parameter">pattern</replaceable> ]</term>

        <listitem>
        <para>
        Lists all available aggregate functions, together with the data
        type they operate on. If <replaceable
        class="parameter">pattern</replaceable> (a regular expression)
        is specified, only matching aggregates are shown.
        </para>
        </listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>\dd</literal> [ <replaceable class="parameter">pattern</replaceable> ]</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>
=> <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
        <command>COMMENT ON</command> <acronym>SQL</acronym> command.
	</para>

        <note>
        <para>
        <productname>PostgreSQL</productname> stores the object
        descriptions in the <structname>pg_description</> system table.
        </para>
        </note>

        </listitem>
      </varlistentry>


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


      <varlistentry>
        <term><literal>\dc</literal> [ <replaceable class="parameter">pattern</replaceable> ]</term>
        <listitem>
        <para>
        Lists all available conversions (between encodings). If <replaceable
        class="parameter">pattern</replaceable>
        is specified, only matching conversions are shown.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\dC</literal></term>
        <listitem>
        <para>
        Lists all available type casts.  Casts can be explicit, explicit and assignment
	or implicit, and are used to change a variable from one type to another.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <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 matching functions are shown. If the form
        <literal>\df+</literal> is used, additional information about
        each function, including language and description, is shown.
        </para>

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

	<listitem>
	<para>
	This is not the actual command name: the letters i, s, t, v, S
	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
	S restricts the listing to system objects; without S, only non-system
	objects are shown.
	If <quote>+</quote> is appended to the command name, each object is
	listed with its associated description, if any.
	</para>

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


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

	<para>
	The commands <xref linkend="SQL-GRANT"> and
	<xref linkend="SQL-REVOKE">
	are used to set access permissions.  See <xref linkend="SQL-GRANT">
	for more information.
	</para>
	</listitem>
      </varlistentry>


      <varlistentry>
        <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 users, or only those that match <replaceable
        class="parameter">pattern</replaceable>.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\edit</literal> (or <literal>\e</literal>) [ <replaceable class="parameter">filename</replaceable> ]</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>/bin/vi</filename> is run.
        </para>
        </tip>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\echo</literal> <replaceable class="parameter">text</replaceable> [ ... ]</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>
=> <userinput>\echo `date`</userinput>
Tue Oct 26 21:40:57 CEST 1999
</programlisting>
        If the first argument is an unquoted <literal>-n</literal> the the trailing
        newline is not written.
	</para>

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


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

        <listitem>
        <para>
        Sets the client encoding, if you are using multibyte encodings.
        Without an argument, this command shows the current encoding.
        </para>
        </listitem>
      </varlistentry>


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

        <listitem>
        <para>
        Sets the field separator for unaligned query output. The default
        is pipe (<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 backend and
        optionally saves the output in <replaceable
        class="parameter">filename</replaceable> or pipes the output
        into a separate Unix shell to execute <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>) [ <replaceable class="parameter">command</replaceable> ]</term>
        <listitem>
        <para>
        Give 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 (<quote>*</quote>), 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</literal> <replaceable class="parameter">filename</replaceable></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>
        <listitem>
        <para>
        List all the databases in the server as well as their owners.
        Append a <quote>+</quote> to the command name to see any
        descriptions for the databases as well. If your
        <productname>PostgreSQL</productname> installation was compiled
        with multibyte encoding support, the encoding scheme of each
        database is shown as well.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\lo_export</literal> <replaceable class="parameter">loid</replaceable> <replaceable class="parameter">filename</replaceable></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>
	<note>
	<para>
	See the description of the <varname>LO_TRANSACTION</varname>
	variable for important information concerning all large object
	operations.
	</para>
	</note>
	</listitem>
      </varlistentry>


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

	<listitem>
	<para>
	Stores the file into a <productname>PostgreSQL</productname>
	<quote>large object</quote>. Optionally, it associates the given
	comment with the object. Example:
<programlisting>
foo=> <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 one ought to remember if one wants to access the
	object ever again. For that reason it is recommended to always
	associate a human-readable comment with every object. Those can
	then be seen 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>

	<note>
	<para>
	See the description of the <varname>LO_TRANSACTION</varname>
	variable for important information concerning all large object
	operations.
	</para>
	</note>
	</listitem>
      </varlistentry>

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

      <varlistentry>
        <term><literal>\lo_unlink</literal> <replaceable class="parameter">loid</replaceable></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>
	<note>
	<para>
	See the description of the <varname>LO_TRANSACTION</varname>
	variable for important information concerning all large object
	operations.
	</para>
	</note>
	</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
        <filename>stdout</filename>.
        </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>\pset</literal> <replaceable class="parameter">parameter</replaceable> [ <replaceable class="parameter">value</replaceable> ]</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>, or
	  <literal>latex</literal>. Unique abbreviations are allowed.
	  (That would mean one letter is enough.)
	  </para>

	  <para>
	  <quote>Unaligned</quote> writes all fields of a tuple 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>
	  Toggles between regular and expanded format. When expanded
	  format is enabled, all output has two columns with the field
	  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 modes.
	  </para>
	  </listitem>
	  </varlistentry>

	  <varlistentry>
	  <term><literal>null</literal></term>
	  <listitem>
	  <para>
	  The second argument is a string that should be printed
	  whenever a field 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 <quote>pipe</quote> symbol).
	  </para>
	  </listitem>
	  </varlistentry>

	  <varlistentry>
	  <term><literal>footer</literal></term>
	  <listitem>
	  <para>
	  Toggles the display of the default footer <literal>(x
	  rows)</literal>.
	  </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>
	  Toggles between tuples only and full display. Full display may
	  show 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</literal> [ <replaceable class="parameter">text</replaceable> ]</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>

	  <note>
	  <para>
	  This formerly only affected <acronym>HTML</acronym> mode. You
	  can now set titles in any output format.
	  </para>
	  </note>
	  </listitem>
	  </varlistentry>

	  <varlistentry>
	  <term><literal>tableattr</literal> (or <literal>T</literal>) [ <replaceable class="parameter">text</replaceable> ]</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.
	  </para>
	  </listitem>
	  </varlistentry>
	</variablelist>
	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>
        Quit the <application>psql</application> program.
        </para>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\qecho</literal> <replaceable class="parameter">text</replaceable> [ ... ] </term>
        <listitem>
        <para>
	This command is identical to <command>\echo</command> except
	that all 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</literal> [ <replaceable class="parameter">filename</replaceable> ]</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> history library.
        </para>

	<note>
	<para>
	In the current version, it is no longer necessary to save the
	command history, since that will be done automatically on
	program termination. The history is also loaded automatically
	every time <application>psql</application> starts up.
	</para>
	</note>
        </listitem>
      </varlistentry>


      <varlistentry>
        <term><literal>\set</literal> [ <replaceable class="parameter">name</replaceable> [ <replaceable class="parameter">value</replaceable> [ ... ]]]</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 about
	<application>psql</application> variables for details.
	</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</literal> <replaceable class="parameter">table_options</replaceable></term>
        <listitem>
        <para>
        Allows you to specify options 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 extended row format mode. As such it is equivalent to
	<literal>\pset expanded</literal>.
       </para>
       </listitem>
      </varlistentry>


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

	<para>
	The commands <xref linkend="SQL-GRANT"> and
	<xref linkend="SQL-REVOKE">
	are used to set access permissions.  See <xref linkend="SQL-GRANT">
	for more information.
	</para>

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


      <varlistentry>
        <term><literal>\!</literal> [ <replaceable class="parameter">command</replaceable> ]</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>
        Get help information about the backslash (<quote>\</quote>)
        commands.
        </para>
        </listitem>
      </varlistentry>

    </variablelist>
  </para>

  <para>
   The various <literal>\d</> commands accept a <replaceable
   class="parameter">pattern</replaceable> parameter to specify the
   object name(s) to be displayed.  Patterns are interpreted similarly
   to SQL identifiers, in that 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>
   More interestingly, <literal>\d</> patterns allow the use of
   <literal>*</> to mean <quote>any sequence of characters</>, and
   <literal>?</> to mean <quote>any single character</>.  (This notation
   is comparable to Unix shell filename patterns.)  Advanced users can
   also use regular-expression notations such as character classes, for
   example <literal>[0-9]</> to match <quote>any digit</>.  To make any of
   these pattern-matching characters be interpreted literally, surround it
   with double quotes.
  </para>

  <para>
   A pattern that contains an (unquoted) dot is interpreted as a schema
   name pattern followed by an object name pattern.  For example,
   <literal> \dt foo*.bar*</> displays all tables in schemas whose name
   starts with <literal>foo</> and whose table name 
   starts with <literal>bar</>.  If no dot appears, then the pattern
   matches only objects that are visible in the current schema search path.
  </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.  To see all objects
   in the database, use the pattern <literal>*.*</>.
  </para>
 </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. This feature is new
    and not very sophisticated, yet, but there are plans to expand it in
    the future. 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=> <userinput>\set foo bar</userinput>
</programlisting>
    sets the variable <quote>foo</quote> to the value
    <quote>bar</quote>. 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=> <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 simply set, but has no 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 regular 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
    such variables. A list of all specially treated variables follows.
    <variablelist>
      <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 <quote><literal>all</literal></quote>, all lines
	entered or from a script are written to the standard output
	before they are parsed or executed. To specify this on program
	start-up, use the switch <option>-a</option>. If set to
	<quote><literal>queries</literal></quote>,
	<application>psql</application> merely prints all queries as
	they are sent to the backend. The option 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. If you set the
	variable to the value <literal>noexec</literal>, the queries are
	just shown but are not actually sent to the backend and
	executed.
	</para>
	</listitem>
      </varlistentry>

      <varlistentry>
        <term><varname>ENCODING</varname></term>
	<listitem>
	<para>
        The current client multibyte encoding. If you are not set up to
        use multibyte characters, this variable will always contain
        <quote>SQL_ASCII</quote>.
	</para>
	</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>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>
        <term><varname>LO_TRANSACTION</varname></term>
	<listitem>
	<para>
	If you use the <productname>PostgreSQL</productname> large
	object interface to specially store data that does not fit into
	one tuple, all the operations must be contained in a transaction
	block. (See the documentation of the large object interface for
	more information.) Since <application>psql</application> has no
	way to tell if you already have a transaction in progress when
	you call one of its internal commands
	(<command>\lo_export</command>, <command>\lo_import</command>,
	<command>\lo_unlink</command>) it must take some arbitrary
	action. This action could either be to roll back any transaction
	that might already be in progress, or to commit any such
	transaction, or to do nothing at all. In the last case you must
	provide your own <command>BEGIN
	TRANSACTION</command>/<command>COMMIT</command> block or the
	results will be unpredictable (usually resulting in the desired
	action's not being performed in any case).
	</para>

	<para>
	To choose what you want to do you set this variable to one of
	<quote>rollback</quote>, <quote>commit</quote>, or
	<quote>nothing</quote>. The default is to roll back the
	transaction. If you just want to load one or a few objects this
	is fine. However, if you intend to transfer many large objects,
	it might be advisable to provide one explicit transaction block
	around all commands.
	</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> query 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 prompt <application>psql</application>
	issues is supposed to look like. See <quote><xref
	linkend="APP-PSQL-prompting"
	endterm="APP-PSQL-prompting-title"></quote> 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 set by the command line option
	<option>-S</option>. You can unset or reset it at run time.
	</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>

    </variablelist>

    </para>

   </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=> <userinput>\set foo 'my_table'</userinput>
testdb=> <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 field. First load the file into a
    variable and then proceed as above.
<programlisting>
testdb=> <userinput>\set content '\'' `cat my_file.txt` '\''</userinput>
testdb=> <userinput>INSERT INTO my_table VALUES (:content);</userinput>
</programlisting>
    One possible 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 third line is processed. This
    could be done with the program <application>sed</application>:
<programlisting>
testdb=> <userinput>\set content '\'' `sed -e "s/'/\\\\\\'/g" < my_file.txt` '\''</userinput>
</programlisting>
    Observe the correct number of backslashes (6)! You can resolve it
    this way: After <application>psql</application> has parsed this
    line, it passes <literal>sed -e "s/'/\\\'/g" < my_file.txt</literal>
    to the shell. The shell will do its own thing inside the double
    quotes and execute <filename>sed</filename> with the arguments
    <literal>-e</literal> and <literal>s/'/\\'/g</literal>. When
    <application>sed</application> parses this it will replace the two
    backslashes with a single one and then do the substitution. Perhaps
    at one point you thought it was great that all Unix commands use the
    same escape character. And this is ignoring the fact that you might
    have to escape all backslashes as well because
    <acronym>SQL</acronym> text constants are also subject to certain
    interpretations. In that case you might be better off preparing the
    file externally.
    </para>

    <para>
    Since colons may legally appear in queries, the following rule
    applies: If the variable is not set, the character sequence
    <quote>colon+name</quote> is not changed. In any case you can escape
    a colon with a backslash to protect it from interpretation. (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 query. Prompt 2 is
    issued when more input is expected during query input because the
    query 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
    tuples on the terminal.
    </para>

    <para>
    The value of the respective prompt variable is printed literally,
    except where a percent sign (<quote>%</quote>) 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 after 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 user name you are connected as (not your local system
         user name).</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 <quote>~</quote>
         (tilde) if the database is your default database.</para></listitem>
      </varlistentry>

      <varlistentry>
        <term><literal>%#</literal></term>
	<listitem><para>If the current user is a database superuser, then a
         <quote>#</quote>, otherwise a <quote>&gt;</quote>.</para></listitem>
      </varlistentry>

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

      <varlistentry>
        <term><literal>%</literal><replaceable class="parameter">digits</replaceable></term>
	<listitem>
	<para>
	If <replaceable class="parameter">digits</replaceable> starts
	with <literal>0x</literal> the rest of the characters are
	interpreted as a hexadecimal digit and the character with the
	corresponding code is substituted. If the first digit is
	<literal>0</literal> the characters are interpreted as on octal
	number and the corresponding character is substituted. Otherwise
	a decimal number is assumed.
	</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 <quote><xref linkend="APP-PSQL-variables"
	endterm="APP-PSQL-variables-title"></quote> 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>

    </variablelist>

    To insert a percent sign into your prompt, write
    <literal>%%</literal>. The default prompts are equivalent to
    <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 stored in a file named <filename>.psql_history</filename>
    in your home directory 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. When available,
    <application>psql</application> is automatically built to use these
    features. If for some reason you do not like the tab completion, you
    can turn if 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>HOME</envar></term>

    <listitem>
     <para>
      Directory for initialization file (<filename>.psqlrc</filename>)
      and command history file (<filename>.psql_history</filename>).
     </para>
    </listitem>
   </varlistentry>

   <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 database to connect to
     </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>
 </refsect1>


 <refsect1>
  <title>Files</title>

  <itemizedlist>
   <listitem>
    <para>
     Before starting up, <application>psql</application> attempts to
     read and execute commands from the file
     <filename>$HOME/.psqlrc</filename>. 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>
     The command-line history is stored in the file
     <filename>$HOME/.psql_history</filename>.
    </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 I am 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=> <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>

      <listitem>
      <para>
      Pressing Control-C during a <quote>copy in</quote> (data sent to
      the server) doesn't show the most ideal of behaviors. If you get a
      message such as <quote>COPY state must be terminated
      first</quote>, simply reset the connection by entering <literal>\c
      - -</literal>.
      </para>
      </listitem>

    </itemizedlist>
 </refsect1>


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

  <note>
  <para>
  This section only shows a few examples specific to
  <application>psql</application>. If you want to learn
  <acronym>SQL</acronym> or get familiar with
  <productname>PostgreSQL</productname>, you might wish to read the
  Tutorial that is included in the distribution.
  </para>
  </note>

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

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

</programlisting>
  You can make this table look differently by using the
  <command>\pset</command> command:
<programlisting>
peter@localhost testdb=> <userinput>\pset border 2</userinput>
Border style is 2.
peter@localhost testdb=> <userinput>SELECT * FROM my_table;</userinput>
+-------+--------+
| first | second |
+-------+--------+
|     1 | one    |
|     2 | two    |
|     3 | three  |
|     4 | four   |
+-------+--------+
(4 rows)

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

peter@localhost testdb=> <userinput>\pset border 1</userinput>
Border style is 1.
peter@localhost testdb=> <userinput>\pset format unaligned</userinput>
Output format is unaligned.
peter@localhost testdb=> <userinput>\pset fieldsep ","</userinput>
Field separator is ",".
peter@localhost testdb=> <userinput>\pset tuples_only</userinput>
Showing only tuples.
peter@localhost testdb=> <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=> <userinput>\a \t \x</userinput>
Output format is aligned.
Tuples only is off.
Expanded display is on.
peter@localhost testdb=> <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>

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