psql1ApplicationpsqlPostgreSQL interactive terminal
psqloptionsdbnameuserDescriptionpsql 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
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.
Switches to unaligned output mode. (The default output mode is
otherwise aligned.)
Specifies that psql is to execute one
query string, query,
and then exit. This is useful in shell scripts.
query must be either
a query string that is completely parsable by the backend (i.e.,
it contains no psql specific features),
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.
Specifies the name of the database to connect to. This is
equivalent to specifying dbname as the first non-option
argument on the command line.
Show all queries that are sent to the backend. This is equivalent
to setting the variable ECHO to
queries.
Echoes the actual queries generated by \d and other backslash
commands. You can use this if you wish to include similar
functionality into your own programs. This is equivalent to
setting the variable ECHO_HIDDEN from within
psql.
Use the file filename
as the source of queries instead of reading queries interactively.
After the file is processed, psql
terminates. This is in many ways equivalent to the internal
command \i.
If filename is -
(hyphen), then standard input is read.
Using this option is subtly different from writing psql
< filename. 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 variant using
the shell's input redirection is (in theory) guaranteed to yield
exactly the same output that you would have gotten had you entered
everything by hand.
Use separator as the
field separator. This is equivalent to \pset
fieldsep or \f.
Specifies the host name of the machine on which the
postmaster is running. If host begins
with a slash, it is used as the directory for the Unix-domain
socket.
Turns on HTML tabular output. This is
equivalent to \pset format html or the
\H command.
Lists all available databases, then exits. Other non-connection
options are ignored. This is similar to the internal command
\list.
Put all query output into file filename. This is equivalent to
the command \o.
Specifies the TCP/IP port or, by omission, the local Unix domain
socket file extension on which the
postmaster 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.
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.
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 option.
Within psql you can also set the
QUIET variable to achieve the same effect.
Use separator as the
record separator. This is equivalent to the \pset
recordsep command.
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.
Runs in single-line mode where a newline terminates a query, as a
semicolon does.
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.
Turn off printing of column names and result row count footers,
etc. It is completely equivalent to the \t
meta-command.
Allows you to specify options to be placed within the
HTML table tag. See
\pset for details.
Makes psql prompt for the user name and
password before connecting 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 backend requires it are really two different
things.) You are encouraged to look at the and
options instead.
Connects to the database as the user username instead of the default.
(You must have permission to do so, of course.)
Performs 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.
Shows the psql version.
Requests that psql 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 \connect.
In the current version, psql
automatically issues a password prompt whenever the backend
requests password authentication. Because this is currently based
on a hack, the automatic recognition might mysteriously fail,
hence this option to force a prompt. If no password prompt is
issued and the backend requires password authentication the
connection attempt will fail.
Turns on extended row format mode. This is equivalent to the
command \x.
Do not read the start-up file ~/.psqlrc.
Shows help about psql command line
arguments.
Long options are not available on all platforms.
Exit Statuspsql 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 ON_ERROR_STOP was set.
UsageConnecting To A Databasepsql 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
, , , and
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
administrator 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, postmaster is not running on the server, etc.),
psql will return an error and terminate.
Entering Queries
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 &version;, the PostgreSQL interactive terminal.
Type: \copyright for distribution terms
\h for help with SQL commands
\? for help on internal slash commands
\g or terminate with semicolon to execute query
\q to quit
testdb=>
At the prompt, the user may type in SQL queries.
Ordinarily, input lines are sent to the backend when a
query-terminating semicolon is reached. An end of line does not
terminate a query! Thus queries can be spread over several lines for
clarity. If the query was sent and without error, the query results
are displayed on the screen.
Whenever a query is executed, psql also polls
for asynchronous notification events generated by
and
.
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-commands 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 characters.
To include whitespace into an argument you may quote it with a
single quote. To include a single quote into such an argument,
precede it by a backslash. Anything contained in single quotes is
furthermore subject to C-like substitutions for
\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 argument. These arguments follow the
syntax rules of SQL regarding double quotes: an
identifier without double quotes is coerced to lower-case, while
whitespace within double quotes is included in the argument.
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 queries, if
any. That way SQL and
psql commands can be freely mixed on a
line. But in any case, the arguments of a meta-command cannot
continue beyond the end of the line.
The following meta-commands are defined:
\a
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 \pset for a
general solution.
\cddirectory
Change the current working directory to
directory. Without argument, change
to the current user's home directory.
To print your current working directory, use \!pwd.
\C [ title ]
Set 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-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.
\copy table
[ ( column_list ) ]
{ from | to }
filename | stdin | stdout
[ with ]
[ oids ]
[ delimiter [as] 'character' ]
[ null [as] 'string' ]
Performs a frontend (client) copy. This is an operation that
runs an SQL command, but instead of the backend's
reading or writing the specified file,
psql reads or writes the file and
routes the data between the backend and the local file system.
This means that file accessibility and privileges are those
of the local user, not the server, and no SQL superuser
privileges are required.
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
command. In particular, the variable substitution rules and
backslash escapes do not apply.
This operation is not as efficient as the SQL
COPY command because all data must pass
through the client/server IP or socket connection. For large
amounts of data the other technique may be preferable.
Note the difference in interpretation of
stdin and stdout between
frontend and backend copies: in a frontend copy these always
refer to psql's input and output
stream. On a backend copy stdin comes from
wherever the COPY itself came from (for
example, a script run with the 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.
If \d is used without a
pattern argument, it is
equivalent 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 (a regular expression)
is specified, only matching aggregates are shown.
\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:
=> \dd version
Object descriptions
Schema | Name | Object | Description
------------+---------+----------+---------------------------
pg_catalog | version | function | PostgreSQL version string
(1 row)
Descriptions for objects can be created with the
COMMENT ON SQL command.
PostgreSQL stores the object
descriptions in the pg_description> system table.
\dD [ pattern ]
Lists all available domains (derived types). If pattern
is specified, only matching domains are shown.
\dc [ pattern ]
Lists all available conversions (between encodings). If pattern
is specified, only matching conversions are shown.
\dC
Lists all available type casts. Casts can be explicit, explicit and assignment
or implicit, and are used to change a variable from one type to another.
\df [ pattern ]
Lists available functions, together with their argument and
return types. If pattern
is specified, only matching functions are shown. If the form
\df+ is used, additional information about
each function, including language and description, is shown.
To reduce clutter, \df> does not show data type I/O
functions. 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 a pattern is
specified, only objects whose name matches the pattern are listed.
\dl
This is an alias for \lo_list, which shows a
list of large objects.
\do [ pattern ]
Lists available operators with their operand and return types.
If a pattern is
specified, only operators whose name matches the pattern are listed.
\dp [ pattern ]
Produces a list of all available tables with their
associated access permissions.
If a pattern is
specified, only tables whose name matches the pattern are listed.
The commands and
are used to set access permissions. See
for more information.
\dT [ pattern ]
Lists all data types or only those that match pattern. The command 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 temporary 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 contains) a semicolon, it is
immediately executed. In other cases it will merely wait in the
query buffer.
psql searches the environment
variables PSQL_EDITOR, EDITOR, and
VISUAL (in that order) for an editor to use. If
all of them are unset, /bin/vi is run.
\echotext [ ... ]
Prints the arguments to the standard output, separated by one
space and followed by a newline. This can be useful to
intersperse information in the output of scripts. For example:
=> \echo `date`
Tue Oct 26 21:40:57 CEST 1999
If the first argument is an unquoted -n the the trailing
newline is not written.
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 encoding, if you are using multibyte encodings.
Without an argument, this command shows the current encoding.
\f [ string ]
Sets the field separator for unaligned query output. The default
is pipe (|). See also
\pset for a generic way of setting output
options.
\g [ { filename | |command } ]
Sends the current query input buffer to the backend and
optionally 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 ]
Give 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.
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.
\ifilename
Reads input from the file filename and executes it as
though it had been typed on the keyboard.
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 all the databases in the server as well as their owners.
Append a + to the command name to see any
descriptions for the databases as well. If your
PostgreSQL installation was compiled
with multibyte encoding support, the encoding scheme of each
database is shown as well.
\lo_exportloidfilename
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.
Use \lo_list to find out the large object's
OID.
See the description of the LO_TRANSACTION
variable for important information concerning all large object
operations.
\lo_importfilename [ comment ]
Stores the file into a PostgreSQLlarge 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.
See the description of the LO_TRANSACTION
variable for important information concerning all large object
operations.
\lo_list
Shows a list of all PostgreSQLlarge objects currently stored in the database,
along with any comments provided for them.
\lo_unlinkloid
Deletes the large object with OID
loid from the
database.
Use \lo_list to find out the large object's
OID.
See the description of the LO_TRANSACTION
variable for important information concerning all large object
operations.
\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
stdout.
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.
To intersperse text output in between query results, use
\qecho.
\p
Print the current query buffer to the standard output.
\psetparameter [ 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 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).
Aligned mode is the standard, human-readable,
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 respective 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 border=... attribute, in the
others only values 0 (no border), 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 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
horizontal mode.
Expanded mode is supported by all four output modes.
null
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 \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 pipe symbol).
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 character.
tuples_only (or t)
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.
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.
This formerly only affected HTML mode. You
can now set titles in any output format.
tableattr (or T) [ text ]
Allows you to specify any attributes to be placed inside the
HTML table tag. This
could for example be cellpadding 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 section.
There are various shortcut commands for \pset. See
\a, \C, \H,
\t, \T, and \x.
It is an error to call \pset without
arguments. In the future this call might show the current status
of all printing options.
\q
Quit the psql program.
\qechotext [ ... ]
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.
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 second
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
underscores. See the section about
psql variables for details.
Although you are welcome to set any variable to anything you
want, psql treats several variables
as special. They are documented in the section about variables.
This command is totally separate from the SQL
command .
\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.
\Ttable_options
Allows you to specify options 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 milliseconds.
\w {filename | |command}
Outputs the current query buffer to the file filename or pipes it to the Unix
command command.
\x
Toggles extended row format mode. As such it is equivalent to
\pset expanded.
\z [ pattern ]
Produces a list of all available tables with their
associated access permissions.
If a pattern is
specified, only tables whose name matches the pattern are listed.
The commands and
are used to set access permissions. See
for more information.
This is an alias for \dp (display
permissions).
\! [ 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.
\?
Get help information about the backslash (\)
commands.
The various \d> commands accept a pattern parameter to specify the
object name(s) to be displayed. Patterns are interpreted similarly
to SQL identifiers, in that unquoted letters are forced to lowercase,
while double quotes (">) protect letters from case conversion
and allow incorporation of whitespace into the identifier. Within
double quotes, paired double quotes reduce to a single double quote in
the resulting name. For example, FOO"BAR"BAZ> is interpreted
as fooBARbaz>, and "A weird"" name"> becomes
A weird" name>.
More interestingly, \d> patterns allow the use of
*> to mean any sequence of characters>, and
?> to mean any single character>. (This notation
is comparable to Unix shell filename patterns.) Advanced users can
also use regular-expression notations such as character classes, for
example [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 pattern
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 featuresVariablespsql provides variable substitution
features similar to common Unix command shells. This feature is new
and not very sophisticated, yet, but there are plans to expand it in
the future. Variables are simply name/value pairs, where the value
can be any string of any length. To set variables, use the
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
The arguments of \set are subject to the same
substitution 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 simply set, but has no 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 regular 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 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.
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 specify this on program
start-up, use the switch . If set to
queries,
psql merely prints all queries as
they are sent to the backend. The option for this is
.
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. If you set the
variable to the value noexec, the queries are
just shown but are not actually sent to the backend and
executed.
ENCODING
The current client multibyte encoding. If you are not set up to
use multibyte characters, this variable will always contain
SQL_ASCII.
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 history list.
This feature was shamelessly plagiarized from
bash.
HISTSIZE
The number of commands to store in the command history. The
default value is 500.
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.
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.
LO_TRANSACTION
If you use the PostgreSQL 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 psql has no
way to tell if you already have a transaction in progress when
you call one of its internal commands
(\lo_export, \lo_import,
\lo_unlink) it must take some arbitrary
action. This action could either be to roll back any transaction
that might already be in progress, or to commit any such
transaction, or to do nothing at all. In the last case you must
provide your own BEGIN
TRANSACTION/COMMIT block or the
results will be unpredictable (usually resulting in the desired
action's not being performed in any case).
To choose what you want to do you set this variable to one of
rollback, commit, or
nothing. 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.
ON_ERROR_STOP
By default, if non-interactive scripts encounter an error, such
as a malformed SQL query 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
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.
PROMPT1PROMPT2PROMPT3
These specify what the prompt psql
issues is supposed to look like. See below.
QUIET
This variable is equivalent to the command line option
. It is probably not too useful in
interactive mode.
SINGLELINE
This variable is set by the command line option
. You can unset or reset it at run time.
SINGLESTEP
This variable is equivalent to the command line option
.
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.
SQL Interpolation
An additional useful feature of psql
variables is that you can substitute (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 backslash commands. You must make sure that it makes sense
where you put it. Variable interpolation will not be performed into
quoted SQL entities.
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 field. 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 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 sed:
testdb=> \set content '\'' `sed -e "s/'/\\\\\\'/g" < my_file.txt` '\''
Observe the correct number of backslashes (6)! You can resolve it
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 backslashes 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 queries, the following rule
applies: If the variable is not set, the character sequence
colon+name 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 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 special escape sequences that describe the appearance of the
prompt. Prompt 1 is the normal prompt that is issued when
psql 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 SQL
COPY command and you are expected to type in the
tuples on the terminal.
The value of the respective prompt variable is printed literally,
except where a percent sign (%) is encountered.
Depending on the next character, certain other text is substituted
instead. Defined substitutions 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 compiled in default
location.
%m
The host name of the database server, truncated after the
first dot, or [local] if the connection is
over a Unix domain socket.
%>The port number at which the database server is listening.%nThe user name you are connected as (not your local system
user name).%/The name of the current database.%~Like %/, but the output is ~
(tilde) if the database is your default database.%#If the current user is a database superuser, then a
#, otherwise a >.%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
query wasn't terminated yet, because you are inside a
/* ... */ comment, or because you are inside
a quote. In prompt 3 the sequence doesn't resolve to anything.
%digits
If digits starts
with 0x the rest of the characters are
interpreted as a hexadecimal digit and the character with the
corresponding code is substituted. If the first digit is
0 the characters are interpreted as on octal
number and the corresponding character is substituted. Otherwise
a decimal number is assumed.
%:name:
The value of the psql, variable
name. See the
section for details.
%`command`
The output of command, similar to ordinary
back-tick substitution.
To insert a percent sign into your prompt, write
%%. The default prompts are equivalent to
'%/%R%# ' for prompts 1 and 2, and
'>> ' for prompt 3.
This feature was shamelessly plagiarized from
tcsh.
Command-Line Editingpsql 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-completion is also
supported, although the completion logic makes no claim to be an
SQL parser. When available,
psql is automatically built to use these
features. If for some reason you do not like the tab completion, you
can turn if off by putting this in a file named
.inputrc 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.)
EnvironmentHOME
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 disabled by
using the \pset command.
PGDATABASE
Default database to connect to
PGHOSTPGPORTPGUSER
Default connection parameters
PSQL_EDITOREDITORVISUAL
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-letter backslash command to start
directly after the command, without intervening whitespace. For
compatibility this is still supported to some extent,
but I am not going to explain the details here as this use is
discouraged. If you get strange messages, keep this in mind.
For example
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 particularly likely to fail if the
server is of a different version.
Pressing Control-C during a copy in (data sent to
the server) doesn't show the most ideal of behaviors. If you get a
message such as COPY state must be terminated
first, simply reset the connection by entering \c
- -.
Examples
This section only shows a few examples specific to
psql. If you want to learn
SQL or get familiar with
PostgreSQL, you might wish to read the
Tutorial that is included in the distribution.
The first example shows how to spread a query 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
Now look at the table definition again:
testdb=> \d my_table
Table "my_table"
Attribute | Type | Modifier
-----------+---------+--------------------
first | integer | not null default 0
second | text |
At this point you decide to 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:
peter@localhost testdb=> SELECT * FROM my_table;
first | second
-------+--------
1 | one
2 | two
3 | three
4 | four
(4 rows)
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:
peter@localhost testdb=> \a \t \x
Output format is aligned.
Tuples only is off.
Expanded display is on.
peter@localhost testdb=> SELECT * FROM my_table;
-[ RECORD 1 ]-
first | 1
second | one
-[ RECORD 2 ]-
first | 2
second | two
-[ RECORD 3 ]-
first | 3
second | three
-[ RECORD 4 ]-
first | 4
second | four