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$Header: /cvsroot/pgsql/doc/src/sgml/ref/psql-ref.sgml,v 1.20 2000/01/14 22:18:01 petere Exp $
Postgres documentation
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<refentry id="APP-PSQL">
<refmeta>
<refentrytitle id="app-psql-title">
<application>psql</application>
</refentrytitle>
<refmiscinfo>Application</refmiscinfo>
</refmeta>
<refnamediv>
<refname>
<application>psql</application>
</refname>
<refpurpose>
<productname>PostgreSQL</productname> interactive terminal
</refpurpose>
</refnamediv>
<refsynopsisdiv>
<refsynopsisdivinfo>
<date>1999-10-26</date>
</refsynopsisdivinfo>
<synopsis>psql [ <replaceable class="parameter">options</replaceable> ] [ <replaceable class="parameter">dbname</replaceable> [ <replaceable class="parameter">user</replaceable> ] ]</synopsis>
<refsect2 id="R2-APP-PSQL-1">
<refsect2info>
<date>1998-09-26</date>
</refsect2info>
<title>Summary</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>
</refsect2>
</refsynopsisdiv>
<refsect1 id="R1-APP-PSQL-1">
<refsect1info>
<date>1998-10-26</date>
</refsect1info>
<title>Description</title>
<refsect2 id="R2-APP-PSQL-connecting">
<refsect2info>
<date>2000-01-14</date>
</refsect2info>
<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 determine
name of you target database, the hostname 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 database name as well. Not all these options are required, defaults do apply.
If you omit the host name psql will connect via domain sockets to a server on the
local host. The default port number is compile-time determined. Since the database
server uses the same default, chances are you don't have to specify the port in most
settings. The default user name is your Unix username, the same with the database.
Note that you can't just connect to any database under any username. 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>, <envar>PGUSER</envar>,
respectively 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">
<refsect2info>
<date>1998-09-26</date>
</refsect2info>
<title>Entering Queries</title>
<para>
In normal operation, <application>psql</application> provides a prompt with
the name of the database that <application>psql</application> is currently
connected to followed by the string "=>". For example,
<programlisting>
$ <userinput>psql testdb</userinput>
Welcome to psql, 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 serveral 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>
</refsect1>
<refsect1 id="R1-APP-PSQL-2">
<refsect1info>
<date>1998-09-26</date>
</refsect1info>
<title><application>psql</application> 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
processes 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 white
space characters.
</para>
<para>
To include whitespace into an argument you must quote it with either single
or double quotes. Anything contained in single quotes (except for a
backslash-escaped single quote itself) is taken literally as the argument.
Anything contained in double 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 dollar sign (<literal>$</literal>),
it is taken as a variable and the value of the variable is taken as the
argument instead. Inside double quotes, variable values can be substituted
by enclosing the name in a <literal>${...}</literal> sequence. See also under
<quote><xref linkend="APP-PSQL-variables" endterm="APP-PSQL-variables-title"></quote>.
</para>
<para>
Arguments that are quoted in <quote>back-ticks</quote> (<literal>`</literal>)
are taken as a command line
that is passed to the shell. The output of the command (with a trailing
newline removed) is taken as the argument value. Back-ticks are subject to
the same substitution rules as double-quotes.
</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.
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>\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 username, 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</literal> <replaceable class="parameter">table</replaceable>
[ <literal>with oids</literal> ] { <literal>from</literal> | <literal>to</literal> }
<replaceable class="parameter">filename</replaceable> | stdin | stdout
[ <literal>with delimiters</literal> '<replaceable class="parameter">characters</replaceable>' ]
[ <literal>with null as</literal> '<replaceable class="parameter">string</replaceable>' ]
</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 reading or writing the specified file, and
consequently requiring backend access and special user privilege,
as well as being bound to the file system accessible by the backend,
<application>psql</application> reads or writes the
file and routes the data to or from the backend onto the local file system.
</para>
<para>
The syntax of the command is in analogy to 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 this 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 whereever the <command>COPY</command>
itself came from (for example, a script ran 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">relation</replaceable> </term>
<listitem>
<para>
Shows all columns of <replaceable class="parameter">relation</replaceable>
(which could be a table, view, index, or sequence),
their types, and any special attributes such as <literal>NOT NULL</literal>
or defaults, if any.
If the relation is, in fact, a table, any defined indices are also listed.
If the relation is a view, the view definition is also shown.
</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 called without any arguments, 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">object</replaceable> ]</term>
<listitem>
<para>
Shows the descriptions of <replaceable class="parameter">object</replaceable>
(which can be a regular expression), or of all objects if no argument is given.
(<quote>Object</quote> covers aggregates, functions, operators, types, relations
(tables, views, indices, sequences, large objects), rules, and triggers.) For example:
<programlisting>
=> <userinput>\dd version</userinput>
Object descriptions
Name | What | Description
---------+----------+---------------------------
version | function | PostgreSQL version string
(1 row)
</programlisting>
</para>
<para>
Descriptions for objects can be generated with the <command>COMMENT ON</command>
<acronym>SQL</acronym> command.
</para>
<note>
<para>
<productname>PostgreSQL</productname> stores the object descriptions in the
pg_description system table.
</para>
</note>
</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>
(a regular expression) 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>
</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 them in any order to obtain a listing of them, together with
who the owner is.
</para>
<para>
If <replaceable class="parameter">pattern</replaceable> is specified,
it is a regular expression restricts the listing to those objects
whose name matches. If one appends a <quote>+</quote> to the command name,
each object is listed with its associated description, if any.
</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 <replaceable class="parameter">pattern</replaceable>
is specified, only operators with that name will be shown.
(Since this is a regular expression, be sure to quote all special
characters in you operator name with backslashes. To prevent
interpretation of the backslash as a new command, you might also
wish to quote the argument.)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>\dp</literal> [ <replaceable class="parameter">pattern</replaceable> ]</term>
<listitem>
<para>
This is an alias for <command>\z</command> which was included for its
greater mnemonic value (<quote>display permissions</quote>).
</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>\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 and after the editor exit 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 <quote>scripts</quote> 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. 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>
</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>\f</literal> [ <replaceable class="parameter">string</replaceable> ]</term>
<listitem>
<para>
Sets the field separator for unaligned query output. The default is <quote><literal>|</literal></quote>
(a <quote>pipe</quote> symbol). 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 <envar>echo</envar>.
</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 <envar>LO_TRANSACTION</envar> 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/me/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 <envar>LO_TRANSACTION</envar> 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 their owners.
</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 <envar>LO_TRANSACTION</envar> 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 pipe 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 support 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
<quote><literal>|</literal></quote> (a <quote>pipe</quote> symbol).
</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 places 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>
Toggles the list of a pager to do table output. If the environment variable
<envar>PAGER</envar> is set, the output is piped to the specified program.
Otherwise <filename>more</filename> is used.
</para>
<para>
In any case, <application>psql</application> only uses the pager if it
seems appropriate. That means among other things that the output is to
a terminal and that the table would normally not fit on the screen.
Because of the modular nature of the printing routines it is not always
possible to predict the number of lines that will actually be printed.
For that reason <application>psql</application> might not appear very
discriminating about when to use the pager and when not to.
</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>
As of <application>psql</application> version 7.0 it is no longer
necessary, in fact, to save the command history as that will be done
automatically on program termination. The history is then
also automatically loaded 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>. If no second argument
is given, the variable is just set with not 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 to,
<application>psql</application> treats several variables 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>\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 tables in the database with their appropriate
access permissions listed. If an argument is given it is taken as a regular
expression which limits the listing to those tables which match it.
</para>
<para>
<programlisting>
test=> <userinput>\z</userinput>
Access permissions for database "test"
Relation | Access permissions
----------+-------------------------------------
my_table | {"=r","joe=arwR", "group staff=ar"}
(1 row )
</programlisting>
Read this as follows:
<itemizedlist>
<listitem>
<para>
<literal>"=r"</literal>: <literal>PUBLIC</literal> has read
(<command>SELECT</command>) permission on the table.
</para>
</listitem>
<listitem>
<para>
<literal>"joe=arwR"</literal>: User <literal>joe</literal> has read,
write (<command>UPDATE</command>, <command>DELETE</command>),
<quote>append</quote> (<command>INSERT</command>) permissions,
and permission to create rules on the table.
</para>
</listitem>
<listitem>
<para>
<literal>"group staff=ar"</literal>: Group <literal>staff</literal>
has <command>SELECT</command> and <command>INSERT</command> permission.
</para>
</listitem>
</itemizedlist>
</para>
<para>
The commands <xref linkend="SQL-GRANT" endterm="SQL-GRANT-title"> and
<xref linkend="SQL-REVOKE" endterm="SQL-REVOKE-title">
are used to set access permissions.
</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. If you wish
to capture the output of a shell command and/or use <application>psql</application>'s
variable substitution features, use the backticks (<literal>`</literal>).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><literal>\?</literal></term>
<listitem>
<para>
Get help information about the slash (<quote>\</quote>) commands.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 id="R1-APP-PSQL-3">
<refsect1info>
<date>1998-09-26</date>
</refsect1info>
<title>Command-line Options</title>
<para>
If so configured, <application>psql</application> understands both standard
Unix short options, and <acronym>GNU</acronym>-style long options. The latter
are not available on all systems.
</para>
<para>
<variablelist>
<varlistentry>
<term>-A, --no-align</term>
<listitem>
<para>
Switches to unaligned output mode. (The default output mode is otherwise
aligned.)
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-c, --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 for shell scripts.
</para>
<para>
<replaceable class="parameter">query</replaceable> must be either a query string
that is completely parseable 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 this you could pipe the string into
<application>psql</application> and finish it with a a <literal>\q</literal>,
like so: <literal>echo "select * from foo; \q" | psql</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-d, --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>-e, --echo</term>
<listitem>
<para>
In non-interactive mode, all lines are printed to the screen as they are read.
This is equivalent to setting the variable <envar>ECHO</envar> to <literal>full</literal>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-E, --echo-hidden</term>
<listitem>
<para>
Echos 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
<envar>ECHO_HIDDEN</envar> from within <application>psql</application>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-f, --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 in many ways equivalent to the internal command <command>\i</command>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-F, --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>-h, --host <replaceable class="parameter">hostname</replaceable></term>
<listitem>
<para>
Specifies the host name of the machine on which the
<application>postmaster</application> is running.
Without this option, communication is performed using
local Unix domain sockets.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-H, --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>-l, --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>-n, --no-readline</term>
<listitem>
<para>
Do not use readline for line editing and do not use the history.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-o, --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>-p, --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>-P, --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>-q</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 <envar>QUIET</envar> variable to achieve the same effect.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-s, --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>-S, --single-line</term>
<listitem>
<para>
Runs in single-line mode where a newline terminates a query, like a semicolon would do.
</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 unexperienced user.
</para>
</note>
</listitem>
</varlistentry>
<varlistentry>
<term>-t, --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>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-T, --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>-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>-U, --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>-v, --variable, --set <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. These assignments are done
during a very early state of startup, so variables reserved for internal purposes
might get overwritten again.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-V, --version</term>
<listitem>
<para>
Shows the <application>psql</application> version.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-W, --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>
As of version 7.0, <application>psql</application> automatically issues a
password prompt whenever the backend requests password authentication.
Because this is currently based on a <quote>hack</quote> 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>-x, --expanded</term>
<listitem>
<para>
Turns on extended row format mode. This is equivalent to the command
<command>\x</command>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term>-?, --help</term>
<listitem>
<para>
Shows help about <application>psql</application> command line arguments.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 id="R1-APP-PSQL-4">
<refsect1info>
<date>1998-09-27</date>
</refsect1info>
<title>Advanced features</title>
<refsect2 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=> <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 dollar-sign and use it
as the argument of any slash command:
<programlisting>
testdb=> <userinput>\echo $foo</userinput>
bar
</programlisting>
Alternatively, the value can also be interpolated into a double-quoted (or backtick-quoted)
string, like so:
<programlisting>
testdb=> <userinput>\echo "foo is now ${foo}."</userinput>
foo is now bar.
</programlisting>
(The curly braces are required.) No variable substitution
will be performed in single-quoted strings or in any of the backslash commands
that have special parsing rules (e.g., <command>\copy</command>).
</para>
<note>
<para>
The arguments of <command>\set</command> are subject to the same substitution
rules as with other commands. Thus you can construct interesting references
such as <literal>\set "${foo}bar" '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 not way to do anything useful
with these constructs. (<literal>\echo ${${foo}}</literal> doesn't work.) 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 an 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 runtime
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><envar>DBNAME</envar></term>
<listitem>
<para>
The name of the database you are currently connected to. This is set everytime
you connect to a database (including program startup), but can be unset.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><envar>ECHO</envar></term>
<listitem>
<para>
If set to <quote><literal>full</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 startup, in conjunction with the
<option>-f</option> option perhaps, use the switch <option>-e</option>.
If set to <quote><literal>brief</literal></quote>, <application>psql</application>
merely prints all queries as they are sent to the backend.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><envar>ECHO_HIDDEN</envar></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 <quote>noexec</quote>, the queries are just shown but are
not actually sent to the backend and executed.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><envar>EXIT_ON_ERROR</envar></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 is has been the traditional behaviour of
<application>psql</application>but is often less than 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><envar>HISTCONTROL</envar></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><envar>HISTSIZE</envar></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><envar>HOST</envar></term>
<listitem>
<para>
The database server host you are currently connected to. This is set everytime
you connect to a database (including program startup), but can be unset.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><envar>IGNOREEOF</envar></term>
<listitem>
<para>
If unset, sending an EOF character (usually Control-D) to an interactive session of
<application>psql</application> will terminate the application.
If set to a numeric value, that many 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><envar>LASTOID</envar></term>
<listitem>
<para>
The value of the last affected oid, as returned from an <command>INSERT</command>
or <command>lo_insert</command> commmand. 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><envar>LO_TRANSACTION</envar></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 keep track 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 latter case you must provide you own
<command>BEGIN TRANSACTION</command>/<command>COMMIT</command> block or
the results will be unpredictable (usually resulting in the desired
action 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><envar>PORT</envar></term>
<listitem>
<para>
The database server port you are currently connected to. This is set everytime
you connect to a database (including program startup), but can be unset.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><envar>PROMPT1</envar>, <envar>PROMPT2</envar>, <envar>PROMPT3</envar></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><envar>QUIET</envar></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><envar>SINGLELINE</envar></term>
<listitem>
<para>
This variable is set be the command line options <option>-S</option>. You
can unset or reset it at run time.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><envar>SINGLESTEP</envar></term>
<listitem>
<para>
This variable is equivalent to the command line option <option>-s</option>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><envar>USER</envar></term>
<listitem>
<para>
The database user you are currently connected as. This is set everytime
you connect to a database (including program startup), but can be unset.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect2>
<refsect2 id="APP-PSQL-sql-interpol">
<title id="APP-PSQL-sql-interpol-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 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 statement 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>\set content "'${content}'"</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 it's 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.)
</para>
</refsect2>
<refsect2 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 <envar>PROMPT1</envar>, <envar>PROMPT2</envar>,
and <envar>PROMPT3</envar> 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 hostname of the database server (or <quote>.</quote> if Unix domain socket).</para></listitem>
</varlistentry>
<varlistentry>
<term><literal>%m</literal></term>
<listitem><para>The hostname of the database server truncated after the first dot.</para></listitem>
</varlistentry>
<varlistentry>
<term><literal>%></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 username 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 username is <literal>postgres</literal>, a <quote>#</quote>, otherwise a <quote>></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 only
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 at a hexadecimal digit and the
character with the corresponding code is subsituted. 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>, <quote>magic</quote>, or environment
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>'>> '</literal> for prompt 3.
</para>
<note>
<para>
This feature was shamelessly plagiarized from <application>tcsh</application>.
</para>
</note>
</refsect2>
<refsect2 id="APP-PSQL-MISC">
<title id="APP-PSQL-MISC-title">Miscellaneous</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 <envar>EXIT_ON_ERROR</envar> was
set.
</para>
<para>
Before starting up in interactive mode, <application>psql</application> attempts
to read and execute the files <filename>/etc/psqlrc</filename> and
<filename>$HOME/.psqlrc</filename>. They could be used to set up the client or
the server to taste (using the <command>\set</command> and <command>SET</command>
commands).
</para>
</refsect2>
<refsect2>
<title><acronym>GNU</acronym> readline</title>
<para>
<application>psql</application> supports the readline and history libraries for
convenienent line editing and retrieval. The command history is stored in a file
named <filename>.psqlrc</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.
</para>
<para>
If you have the readline library installed but <application>psql</application>
does not seem to use it, you must make sure that <productname>PostgreSQL</productname>'s
top-level <filename>configure</filename> script finds it. <filename>configure</filename>
needs to find both the library <filename>libreadline.a</filename>
(or <filename>libreadline.so</filename> on systems with shared libraries)
<emphasis>and</emphasis> the header files <filename>readline.h</filename> and
<filename>history.h</filename> (or <filename>readline/readline.h</filename> and
<filename>readline/history.h</filename>) in appropriate directories. If
you have the library and header files installed in an obscure place you
must tell <filename>configure</filename> about them, for example:
<programlisting>
$ ./configure --with-includes=/opt/gnu/include --with-libraries=/opt/gnu/lib ...
</programlisting>
Then you have to recompile <application>psql</application> (not necessarily
the entire code tree).
</para>
<para>
The <acronym>GNU</acronym> readline library can be obtained from the <acronym>GNU</acronym>
project's <acronym>FTP</acronym> server at <ulink URL="ftp://ftp.gnu.org">ftp://ftp.gnu.org</ulink>.
</para>
</refsect2>
</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 int4 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 | Info
-----------+------+--------------------
first | int4 | 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>
Notice how the int4 colums in right aligned while the text column in left aligned.
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>
<refsect1>
<refsect1info>
<date>1999-10-27</date>
</refsect1info>
<title>Appendix</title>
<refsect2>
<title>Bugs and Issues</title>
<itemizedlist>
<listitem>
<para>
In some earlier life <application>psql</application> allowed the first
argument to start directly after the (single-letter) command. For
compatibility this is still supported to some extent but I am not
going to explain the details here as this use is discouraged. But
if you get strange messages, keep this in mind. For example
<programlisting>
testdb=> <userinput>\foo</userinput>
Field separator is "oo".
</programlisting>
is perhaps not what one would expect.
</para>
</listitem>
<listitem>
<para>
<application>psql</application> only works smootly 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.
</para>
</listitem>
<listitem>
<para>
The number of options for a backslash command is limited, probably to 16.
You can easily change this in the source code, and perhaps I will get around
to fixing this one day. Not that there is any command
that actually uses that many options though.
</para>
</listitem>
</itemizedlist>
</refsect2>
</refsect1>
</refentry>
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