psql

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PSQL(1) PostgreSQL Client Applications PSQL(1)

NAME
psql - PostgreSQL interactive terminal

SYNOPSIS
psql [ option... ] [ dbname
[ username ] ]

DESCRIPTION
psql is a terminal-based front-end to PostgreSQL. It enables you to
type in queries interactively, issue them to PostgreSQL, 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.

OPTIONS
-a

--echo-all
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 ECHO to all.

-A

--no-align
Switches to unaligned output mode. (The default output mode is
otherwise aligned.)

-c command

--command command
Specifies that psql is to execute one command string, command,
and then exit. This is useful in shell scripts.

command must be either a command string that is completely
parsable by the server (i.e., it contains no psql specific fea-
tures), or it is a single backslash command. Thus you cannot
mix SQL and psql meta-commands. To achieve that, you could pipe
the string into psql, like this: echo "\x \\ select * from
foo;" | psql.

If the command string contains multiple SQL commands, they are
processed in a single transaction, unless there are explicit
BEGIN/COMMIT commands included in the string to divide it into
multiple transactions. This is different from the behavior when
the same string is fed to psql’s standard input.

-d dbname

--dbname dbname
Specifies the name of the database to connect to. This is
equivalent to specifying dbname as the first non-option argu-
ment on the command line.

-e

--echo-queries
Show all commands that are sent to the server. This is equiva-
lent to setting the variable ECHO to queries.

-E

--echo-hidden
Echo the actual queries generated by \d and other backslash
commands. You can use this if you wish to include similar func-
tionality into your own programs. This is equivalent to setting
the variable ECHO_HIDDEN from within psql.

-f filename

--file filename
Use the file filename as the source of commands instead of
reading commands interactively. After the file is processed,
psql terminates. This is in many ways equivalent to the inter-
nal command \i.

If filename is - (hyphen), then standard input is read.

Using this option is subtly different from writing psql < file-
name. In general, both will do what you expect, but using -f
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 vari-
ant using the shell’s input redirection is (in theory) guaran-
teed to yield exactly the same output that you would have got-
ten had you entered everything by hand.

-F separator

--field-separator separator
Use separator as the field separator. This is equivalent to
\pset fieldsep or \f.

-h hostname

--host hostname
Specifies the host name of the machine on which the server is
running. If the value begins with a slash, it is used as the
directory for the Unix-domain socket.

-H

--html Turn on HTML tabular output. This is equivalent to \pset format
html or the \H command.

-l

--list List all available databases, then exits. Other non-connection
options are ignored. This is similar to the internal command
\list.

-o filename

--output filename
Put all query output into file filename. This is equivalent to
the command \o.

-p port

--port port
Specifies the TCP port or the local Unix domain socket file
extension on which the server is listening for connections.
Defaults to the value of the PGPORT environment variable or, if
not set, to the port specified at compile time, usually 5432.

-P assignment

--pset assignment
Allows you to specify printing options in the style of \pset 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 -P format=latex.

-q

--quiet
Specifies that psql 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 -c option. Within psql you can also set the QUIET variable
to achieve the same effect.

-R separator

--record-separator separator
Use separator as the record separator. This is equivalent to
the \pset recordsep command.

-s

--single-step
Run in single-step mode. That means the user is prompted before
each command is sent to the server, with the option to cancel
execution as well. Use this to debug scripts.

-S

--single-line
Runs in single-line mode where a newline terminates an SQL com-
mand, as a semicolon does.

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

-t

--tuples-only
Turn off printing of column names and result row count footers,
etc. It is completely equivalent to the \t meta-command.

-T table_options

--table-attr table_options
Allows you to specify options to be placed within the HTML ta-
ble tag. See \pset for details.

-u Makes psql prompt for the user name and password before con-
necting to the database.

This option is deprecated, as it is conceptually flawed.
(Prompting for a non-default user name and prompting for a
password because the server requires it are really two differ-
ent things.) You are encouraged to look at the -U and -W
options instead.

-U username

--username username
Connect to the database as the user username instead of the
default. (You must have permission to do so, of course.)

-v assignment

--set assignment

--variable assignment
Perform a variable assignment, like the \set 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.

-V

--version
Show the psql version.

-W

--password
Requests that psql should prompt for a password before connect-
ing to a database. This will remain set for the entire session,
even if you change the database connection with the meta-com-
mand \connect.

In the current version, psql automatically issues a password
prompt whenever the server requests password authentication.
Because this is currently based on a hack, the automatic recog-
nition might mysteriously fail, hence this option to force a
prompt. If no password prompt is issued and the server requires
password authentication the connection attempt will fail.

-x

--expanded
Turn on the extended table formatting mode. This is equivalent
to the command \x.

-X,

--no-psqlrc
Do not read the start-up file ~/.psqlrc.

--help Show help about psql command line arguments.

EXIT STATUS
psql 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 con-
nection to the server went bad and the session was not interactive,
and 3 if an error occurred in a script and the variable ON_ERROR_STOP
was set.

USAGE
CONNECTING TO A DATABASE
psql is a regular PostgreSQL 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. psql can be told about those parameters via command line
options, namely -d, -h, -p, and -U 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, 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 administra-
tor should have informed you about your access rights. To save you
some typing you can also set the environment variables PGDATABASE,
PGHOST, PGPORT and PGUSER to appropriate values.

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

ENTERING SQL COMMANDS
In normal operation, psql provides a prompt with the name of the
database to which psql is currently connected, followed by the string
=>. For example,

$ psql testdb
Welcome to psql 7.4.19, 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=>

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

Whenever a command is executed, psql also polls for asynchronous noti-
fication events generated by LISTEN [listen(7)] and NOTIFY
[notify(7)].

META-COMMANDS
Anything you enter in psql that begins with an unquoted backslash is a
psql meta-command that is processed by psql itself. These commands are
what makes psql interesting for administration or scripting. Meta-com-
mands are more commonly called slash or backslash commands.

The format of a psql 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 charac-
ters.

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 sub-
ject to C-like substitutions for \n (new line), \t (tab), \digits,
\0digits, and \0xdigits (the character with the given decimal, octal,
or hexadecimal code).

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

Arguments that are enclosed in backquotes (‘) 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.

Some commands take an SQL identifier (such as a table name) as argu-
ment. These arguments follow the syntax rules of SQL: Unquoted letters
are forced to lowercase, while double quotes (") protect letters from
case conversion and allow incorporation of whitespace into the identi-
fier. Within double quotes, paired double quotes reduce to a single
double quote in the resulting name. For example, FOO"BAR"BAZ is inter-
preted as fooBARbaz, and "A weird"" name" becomes A weird" name.

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

The following meta-commands are defined:

\a If the current table output format is unaligned, it is switched
to aligned. If it is not unaligned, it is set to unaligned.
This command is kept for backwards compatibility. See \pset for
a general solution.

\cd [directory]
Changes the current working directory to directory. Without
argument, changes to the current user’s home directory.

Tip: To print your current working directory, use \!pwd.

\C [ title ]
Sets the title of any tables being printed as the result of a
query or unset any such title. This command is equivalent to
\pset title title. (The name of this command derives from
‘‘caption’’, as it was previously only used to set the caption
in an HTML table.)

\connect (or \c) [ dbname [ username ] ]
Establishes a connection to a new database and/or under a user
name. The previous connection is closed. If dbname is - the
current database name is assumed.

If username is omitted the current user name is assumed.

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

If the connection attempt failed (wrong user name, access
denied, etc.), the previous connection will be kept if and only
if psql is in interactive mode. When executing a non-interac-
tive 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.

\copy table
Performs a frontend (client) copy. This is an operation that
runs an SQL COPY [copy(7)] command, but instead of the server
reading or writing the specified file, psql reads or writes the
file and routes the data between the server and the local file
system. This means that file accessibility and privileges are
those of the local user, not the server, and no SQL superuser
privileges are required.

The syntax of the command is similar to that of the SQL COPY
command. (See its description for the details.) Note that,
because of this, special parsing rules apply to the \copy com-
mand. In particular, the variable substitution rules and back-
slash escapes do not apply.

Tip: This operation is not as efficient as the SQL COPY command
because all data must pass through the client/server connec-
tion. For large amounts of data the other technique may be
preferable.

Note: Note the difference in interpretation of stdin and stdout
between client and server copies: in a client copy these always
refer to psql’s input and output stream. On a server copy stdin
comes from wherever the COPY itself came from (for example, a
script run with the -f option), and stdout refers to the query
output stream (see \o meta-command below).

\copyright
Shows the copyright and distribution terms of PostgreSQL.

\d [ pattern ]
For each relation (table, view, index, or sequence) matching
the pattern, show all columns, their types, and any special
attributes such as NOT NULL or defaults, if any. Associated
indexes, constraints, rules, and triggers are also shown, as is
the view definition if the relation is a view. (‘‘Matching the
pattern’’ is defined below.)

The command form \d+ is identical, but any comments associated
with the table columns are shown as well.

Note: If \d is used without a pattern argument, it is equiva-
lent to \dtvs which will show a list of all tables, views, and
sequences. This is purely a convenience measure.

\da [ pattern ]
Lists all available aggregate functions, together with the data
type they operate on. If pattern is specified, only aggregates
whose names match the pattern are shown.

\dc [ pattern ]
Lists all available conversions between character-set encod-
ings. If pattern is specified, only conversions whose names
match the pattern are listed.

\dC Lists all available type casts.

\dd [ pattern ]
Shows the descriptions of objects matching the pattern, or of
all visible objects if no argument is given. But in either
case, only objects that have a description are listed.
(‘‘Object’’ covers aggregates, functions, operators, types,
relations (tables, views, indexes, sequences, large objects),
rules, and triggers.) For example:

Descriptions for objects can be created with the COMMENT SQL
command.

\dD [ pattern ]
Lists all available domains. If pattern is specified, only
matching domains are shown.

\df [ pattern ]
Lists available functions, together with their argument and
return types. If pattern is specified, only functions whose
names match the pattern are shown. If the form \df+ is used,
additional information about each function, including language
and description, is shown.

Note: To reduce clutter, \df does not show data type I/O func-
tions. This is implemented by ignoring functions that accept or
return type cstring.

\distvS [ pattern ]
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 + is appended to the
command name, each object is listed with its associated
description, if any.

If pattern is specified, only objects whose names match the
pattern are listed.

\dl This is an alias for \lo_list, which shows a list of large
objects.

\dn [ pattern ]
Lists all available schemas (namespaces). If pattern (a regular
expression) is specified, only schemas whose names match the
pattern are listed.

\do [ pattern ]
Lists available operators with their operand and return types.
If pattern is specified, only operators whose names match the
pattern are listed.

\dp [ pattern ]
Produces a list of all available tables with their associated
access privileges. If pattern is specified, only tables whose
names match the pattern are listed.

The commands grant(7) and revoke(7) are used to set access
privileges. See grant(7) for more information.

\dT [ pattern ]
Lists all data types or only those that match pattern. The com-
mand form \dT+ shows extra information.

\du [ pattern ]
Lists all database users or only those that match pattern.

\edit (or \e) [ filename ]
If filename 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 tem-
porary file which is then edited in the same fashion.

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

Tip: psql searches the environment variables PSQL_EDITOR, EDI-
TOR, and VISUAL (in that order) for an editor to use. If all of
them are unset, /bin/vi is run.

\echo text [ ... ]
Prints the arguments to the standard output, separated by one
space and followed by a newline. This can be useful to inter-
sperse information in the output of scripts. For example:

=> \echo ‘date‘
Tue Oct 26 21:40:57 CEST 1999

If the first argument is an unquoted -n the the trailing new-
line is not written.

Tip: If you use the \o command to redirect your query output
you may wish to use \qecho instead of this command.

\encoding [ encoding ]
Sets the client character set encoding. Without an argument,
this command shows the current encoding.

\f [ string ]
Sets the field separator for unaligned query output. The
default is the vertical bar (|). See also \pset for a generic
way of setting output options.

\g [ { filename | |command } ]
Sends the current query input buffer to the server and option-
ally saves the output in filename or pipes the output into a
separate Unix shell to execute command. A bare \g is virtually
equivalent to a semicolon. A \g with argument is a ‘‘one-shot’’
alternative to the \o command.

\help (or \h) [ command ]
Gives syntax help on the specified SQL command. If command is
not specified, then psql will list all the commands for which
syntax help is available. If command is an asterisk (*), then
syntax help on all SQL commands is shown.

Note: To simplify typing, commands that consists of several
words do not have to be quoted. Thus it is fine to type \help
alter table.

\H Turns on HTML query output format. If the HTML format is
already on, it is switched back to the default aligned text
format. This command is for compatibility and convenience, but
see \pset about setting other output options.

\i filename
Reads input from the file filename and executes it as though it
had been typed on the keyboard.

Note: If you want to see the lines on the screen as they are
read you must set the variable ECHO to all.

\l (or \list)
List the names, owners, and character set encodings of all the
databases in the server. Append a + to the command name to see
any descriptions for the databases as well.

\lo_export loid filename
Reads the large object with OID loid from the database and
writes it to filename. Note that this is subtly different from
the server function lo_export, which acts with the permissions
of the user that the database server runs as and on the
server’s file system.

Tip: Use \lo_list to find out the large object’s OID.

\lo_import filename [ comment ]
Stores the file into a PostgreSQL large object. Optionally, it
associates the given comment with the object. Example:

foo=> \lo_import ’/home/peter/pictures/photo.xcf’ ’a picture of me’
lo_import 152801

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 \lo_list command.

Note that this command is subtly different from the server-side
lo_import because it acts as the local user on the local file
system, rather than the server’s user and file system.

\lo_list
Shows a list of all PostgreSQL large objects currently stored
in the database, along with any comments provided for them.

\lo_unlink loid
Deletes the large object with OID loid from the database.

Tip: Use \lo_list to find out the large object’s OID.

\o [ {filename | |command} ]
Saves future query results to the file filename or pipes future
results into a separate Unix shell to execute command. If no
arguments are specified, the query output will be reset to the
standard output.

‘‘Query results’’ 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
\d), but not error messages.

Tip: To intersperse text output in between query results, use
\qecho.

\p Print the current query buffer to the standard output.

\pset parameter [ value ]
This command sets options affecting the output of query result
tables. parameter describes which option is to be set. The
semantics of value depend thereon.

Adjustable printing options are:

format Sets the output format to one of unaligned, aligned,
html, or latex. Unique abbreviations are allowed. (That
would mean one letter is enough.)

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

border 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
HTML mode, this will translate directly into the bor-
der=... attribute, in the others only values 0 (no bor-
der), 1 (internal dividing lines), and 2 (table frame)
make sense.

expanded (or x)
Toggles between regular and expanded format. When
expanded format is enabled, all output has two columns
with the column name on the left and the data on the
right. This mode is useful if the data wouldn’t fit on
the screen in the normal ‘‘horizontal’’ mode.

Expanded mode is supported by all four output formats.

null The second argument is a string that should be printed
whenever a column is null. The default is not to print
anything, which can easily be mistaken for, say, an
empty string. Thus, one might choose to write \pset null
’(null)’.

fieldsep
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 \pset
fieldsep ’\t’. The default field separator is ’|’ (a
vertical bar).

footer Toggles the display of the default footer (x rows).

recordsep
Specifies the record (line) separator to use in
unaligned output mode. The default is a newline charac-
ter.

tuples_only (or t)
Toggles between tuples only and full display. Full dis-
play may show extra information such as column headers,
titles, and various footers. In tuples only mode, only
actual table data is shown.

title [ text ]
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.

tableattr (or T) [ text ]
Allows you to specify any attributes to be placed inside
the HTML table tag. This could for example be cell-
padding or bgcolor. Note that you probably don’t want to
specify border here, as that is already taken care of by
\pset border.

pager Controls use of a pager for query and psql help output.
If the environment variable PAGER is set, the output is
piped to the specified program. Otherwise a platform-
dependent default (such as more) is used.

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. (psql does not do a perfect job of estimating
when to use the pager.) \pset pager turns the pager on
and off. Pager can also be set to always, which causes
the pager to be always used.

Illustrations on how these different formats look can be seen in the
Examples [psql(1)] section.

Tip: There are various shortcut commands for \pset. See \a, \C,
\H, \t, \T, and \x.

Note: It is an error to call \pset without arguments. In the
future this call might show the current status of all printing
options.

\q Quits the psql program.

\qecho text [ ... ]
This command is identical to \echo except that all output will
be written to the query output channel, as set by \o.

\r Resets (clears) the query buffer.

\s [ filename ]
Print or save the command line history to filename. If filename
is omitted, the history is written to the standard output. This
option is only available if psql is configured to use the GNU
history library.

Note: 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 psql starts up.

\set [ name [ value [ ... ]]]
Sets the internal variable name to value or, if more than one
value is given, to the concatenation of all of them. If no sec-
ond argument is given, the variable is just set with no value.
To unset a variable, use the \unset command.

Valid variable names can contain characters, digits, and under-
scores. See the section Variables [psql(1)] below for details.

Although you are welcome to set any variable to anything you
want, psql treats several variables as special. They are docu-
mented in the section about variables.

Note: This command is totally separate from the SQL command SET
[set(7)].

\t Toggles the display of output column name headings and row
count footer. This command is equivalent to \pset tuples_only
and is provided for convenience.

\T table_options
Allows you to specify attributes to be placed within the table
tag in HTML tabular output mode. This command is equivalent to
\pset tableattr table_options.

\timing
Toggles a display of how long each SQL statement takes, in mil-
liseconds.

\w {filename | |command}
Outputs the current query buffer to the file filename or pipes
it to the Unix command command.

\x Toggles extended table formatting mode. As such it is equiva-
lent to \pset expanded.

\z [ pattern ]
Produces a list of all available tables with their associated
access privileges. If a pattern is specified, only tables
whose names match the pattern are listed.

The commands grant(7) and revoke(7) are used to set access
privileges. See grant(7) for more information.

This is an alias for \dp (‘‘display privileges’’).

\! [ command ]
Escapes to a separate Unix shell or executes the Unix command
command. The arguments are not further interpreted, the shell
will see them as is.

\? Shows help information about the backslash commands.

The various \d commands accept a pattern parameter to specify the
object name(s) to be displayed. * means ‘‘any sequence of characters’’
and ? means ‘‘any single character’’. (This notation is comparable to
Unix shell file name patterns.) Advanced users can also use regular-
expression notations such as character classes, for example [0-9] to
match ‘‘any digit’’. To make any of these pattern-matching characters
be interpreted literally, surround it with double quotes.

A pattern that contains an (unquoted) dot is interpreted as a schema
name pattern followed by an object name pattern. For example, \dt
foo*.bar* displays all tables in schemas whose name starts with foo
and whose table name starts with bar. If no dot appears, then the pat-
tern matches only objects that are visible in the current schema
search path.

Whenever the pattern parameter is omitted completely, the \d commands
display all objects that are visible in the current schema search
path. To see all objects in the database, use the pattern *.*.

ADVANCED FEATURES
VARIABLES
psql 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 psql
meta-command \set:

testdb=> \set foo bar

sets the variable foo to the value bar. To retrieve the content of the
variable, precede the name with a colon and use it as the argument of
any slash command:

testdb=> \echo :foo
bar

Note: The arguments of \set are subject to the same substitu-
tion rules as with other commands. Thus you can construct
interesting references such as \set :foo ’something’ and get
‘‘soft links’’ or ‘‘variable variables’’ of Perl or PHP fame,
respectively. Unfortunately (or fortunately?), there is no way
to do anything useful with these constructs. On the other hand,
\set bar :foo is a perfectly valid way to copy a variable.

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

psql’s internal variable names can consist of letters, numbers, and
underscores in any order and any number of them. A number of these
variables are treated specially by psql. 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 con-
vention, all specially treated variables consist of all upper-case
letters (and possibly numbers and underscores). To ensure maximum com-
patibility in the future, avoid using such variable names for your own
purposes. A list of all specially treated variables follows.

AUTOCOMMIT
When on (the default), each SQL command is automatically com-
mitted upon successful completion. To postpone commit in this
mode, you must enter a BEGIN or START TRANSACTION SQL command.
When off or unset, SQL commands are not committed until you
explicitly issue COMMIT or END. The autocommit-off mode works
by issuing an implicit BEGIN for you, just before any command
that is not already in a transaction block and is not itself a
BEGIN or other transaction-control command.

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

Note: The autocommit-on mode is PostgreSQL’s traditional behav-
ior, but autocommit-off is closer to the SQL spec. If you pre-
fer autocommit-off, you may wish to set it in your .psqlrc
file.

DBNAME 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.

ECHO If set to all, all lines entered or from a script are written
to the standard output before they are parsed or executed. To
select this behavior on program start-up, use the switch -a. If
set to queries, psql merely prints all queries as they are sent
to the server. The switch for this is -e.

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

ENCODING
The current client character set encoding.

HISTCONTROL
If this variable is set to ignorespace, lines which begin with
a space are not entered into the history list. If set to a
value of ignoredups, lines matching the previous history line
are not entered. A value of ignoreboth 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 his-
tory list.

Note: This feature was shamelessly plagiarized from Bash.

HISTSIZE
The number of commands to store in the command history. The
default value is 500.

Note: This feature was shamelessly plagiarized from Bash.

HOST 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.

IGNOREEOF
If unset, sending an EOF character (usually Control+D) to an
interactive session of psql 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.

Note: This feature was shamelessly plagiarized from Bash.

LASTOID
The value of the last affected OID, as returned from an INSERT
or lo_insert command. This variable is only guaranteed to be
valid until after the result of the next SQL command has been
displayed.

ON_ERROR_STOP
By default, if non-interactive scripts encounter an error, such
as a malformed SQL command or internal meta-command, processing
continues. This has been the traditional behavior of psql 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 psql
session but rather using the -f option, psql will return error
code 3, to distinguish this case from fatal error conditions
(error code 1).

PORT 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.

PROMPT1

PROMPT2

PROMPT3
These specify what the prompts psql issues should look like.
See Prompting [psql(1)] below.

QUIET This variable is equivalent to the command line option -q. It
is probably not too useful in interactive mode.

SINGLELINE
This variable is equivalent to the command line option -S.

SINGLESTEP
This variable is equivalent to the command line option -s.

USER 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.

VERBOSITY
This variable can be set to the values default, verbose, or
terse to control the verbosity of error reports.

SQL INTERPOLATION
An additional useful feature of psql variables is that you can substi-
tute (‘‘interpolate’’) them into regular SQL statements. The syntax
for this is again to prepend the variable name with a colon (:).

testdb=> \set foo ’my_table’
testdb=> SELECT * FROM :foo;

would then query the table my_table. The value of the variable is
copied literally, so it can even contain unbalanced quotes or back-
slash commands. You must make sure that it makes sense where you put
it. Variable interpolation will not be performed into quoted SQL enti-
ties.

A popular application of this facility is to refer to the last
inserted OID in subsequent statements to build a foreign key scenario.
Another possible use of this mechanism is to copy the contents of a
file into a table column. First load the file into a variable and then
proceed as above.

testdb=> \set content ’\’’ ‘cat my_file.txt‘ ’\’’
testdb=> INSERT INTO my_table VALUES (:content);

One possible problem with this approach is that my_file.txt might con-
tain single quotes. These need to be escaped so that they don’t cause
a syntax error when the second line is processed. This could be done
with the program sed:

testdb=> \set content ’\’’ ‘sed -e "s/’/\\\\\\’/g" < my_file.txt‘ ’\’’

Observe the correct number of backslashes (6)! It works this way:
After psql has parsed this line, it passes sed -e "s/’/\\\’/g" <
my_file.txt to the shell. The shell will do its own thing inside the
double quotes and execute sed with the arguments -e and s/’/\\’/g.
When sed 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 back-
slashes as well because SQL text constants are also subject to certain
interpretations. In that case you might be better off preparing the
file externally.

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

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

The value of the selected prompt variable is printed literally, except
where a percent sign (%) is encountered. Depending on the next char-
acter, certain other text is substituted instead. Defined substitu-
tions are:

%M The full host name (with domain name) of the database server,
or [local] if the connection is over a Unix domain socket, or
[local:/dir/name], if the Unix domain socket is not at the com-
piled in default location.

%m The host name of the database server, truncated at the first
dot, or [local] if the connection is over a Unix domain socket.

%> The port number at which the database server is listening.

%n The database session user name. (The expansion of this value
might change during a database session as the result of the
command SET SESSION AUTHORIZATION.)

%/ The name of the current database.

%~ Like %/, but the output is ~ (tilde) if the database is your
default database.

%# If the session user is a database superuser, then a #, other-
wise a >. (The expansion of this value might change during a
database session as the result of the command SET SESSION
AUTHORIZATION.)

%R In prompt 1 normally =, but ^ if in single-line mode, and ! if
the session is disconnected from the database (which can happen
if \connect fails). In prompt 2 the sequence is replaced by -,
*, a single quote, or a double quote, depending on whether psql
expects more input because the command wasn’t terminated yet,
because you are inside a /* ... */ comment, or because you are
inside a quote. In prompt 3 the sequence doesn’t produce any-
thing.

%x Transaction status: an empty string when not in a transaction
block, or * when in a transaction block, or ! when in a failed
transaction block, or ? when the transaction state is indeter-
minate (for example, because there is no connection).

%digits
The character with the indicated numeric code is substituted.
If digits starts with 0x the rest of the characters are inter-
preted as hexadecimal; otherwise if the first digit is 0 the
digits are interpreted as octal; otherwise the digits are read
as a decimal number.

%:name:
The value of the psql variable name. See the section Variables
[psql(1)] for details.

%‘command‘
The output of command, similar to ordinary ‘‘back-tick’’ sub-
stitution.

To insert a percent sign into your prompt, write %%. The default
prompts are ’%/%R%# ’ for prompts 1 and 2, and ’>> ’ for prompt 3.

Note: This feature was shamelessly plagiarized from tcsh.

COMMAND-LINE EDITING
psql supports the Readline library for convenient line editing and
retrieval. The command history is stored in a file named .psql_history
in your home directory and is reloaded when psql starts up. Tab-com-
pletion is also supported, although the completion logic makes no
claim to be an SQL parser. If for some reason you do not like the tab
completion, you can turn if off by putting this in a file named .inpu-
trc in your home directory:

$if psql
set disable-completion on
$endif

(This is not a psql but a Readline feature. Read its documentation for
further details.)

ENVIRONMENT
HOME Directory for initialization file (.psqlrc) and command history
file (.psql_history).

PAGER If the query results do not fit on the screen, they are piped
through this command. Typical values are more or less. The
default is platform-dependent. The use of the pager can be dis-
abled by using the \pset command.

PGDATABASE
Default database to connect to

PGHOST

PGPORT

PGUSER Default connection parameters

PSQL_EDITOR

EDITOR

VISUAL Editor used by the \e command. The variables are examined in
the order listed; the first that is set is used.

SHELL Command executed by the \! command.

TMPDIR Directory for storing temporary files. The default is /tmp.

FILES
· Before starting up, psql attempts to read and execute commands from
the file $HOME/.psqlrc. It could be used to set up the client or the
server to taste (using the \set and SET commands).

· The command-line history is stored in the file $HOME/.psql_history.

NOTES
· In an earlier life psql allowed the first argument of a single-let-
ter backslash command to start directly after the command, without
intervening whitespace. For compatibility this is still supported to
some extent, but were are not going to explain the details here as
this use is discouraged. If you get strange messages, keep this in
mind. For example

testdb=> \foo
Field separator is "oo".

which is perhaps not what one would expect.

· psql 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 particu-
larly likely to fail if the server is of a different version.

EXAMPLES
The first example shows how to spread a command over several lines of
input. Notice the changing prompt:

testdb=> CREATE TABLE my_table (
testdb(> first integer not null default 0,
testdb(> second text
testdb-> );
CREATE TABLE

Now look at the table definition again:

Now we change the prompt to something more interesting:

testdb=> \set PROMPT1 ’%n@%m %~%R%# ’
peter@localhost testdb=>

Let’s assume you have filled the table with data and want to take a
look at it:

You can make this table look differently by using the \pset command:

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

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

peter@localhost testdb=> \pset border 1
Border style is 1.
peter@localhost testdb=> \pset format unaligned
Output format is unaligned.
peter@localhost testdb=> \pset fieldsep ","
Field separator is ",".
peter@localhost testdb=> \pset tuples_only
Showing only tuples.
peter@localhost testdb=> SELECT second, first FROM my_table;
one,1
two,2
three,3
four,4

Alternatively, use the short commands:

Application 2008-01-03 PSQL(1)