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PSQL(1)
NAME
psql - PostgreSQL interactive terminal
SYNOPSIS
psql [ options ] [ dbname [ user ] ]
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 query
--command query
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.
-d dbname
--dbname dbname
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.
-e
--echo-queries
Show all queries that are sent to the backend. This is equivalent to
setting the variable ECHO to queries.
-E
--echo-hidden
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.
-f filename
--file filename
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.
-F separator
--field-separator separator
Use separator as the field separator. This is equivalent to \pset
fieldsep or \f\!>fR.
-h hostname
--host hostname
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.
-H
--html
Turns on HTML tabular output. This is equivalent to \pset format html
or the \H command.
-l
--list
Lists 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/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.
-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
query is sent to the backend, 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 a query, 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 table tag.
See \pset for details.
-u 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 -U and -W options instead.
-U username
--username username
Connects 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
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.
-V
--version
Shows the psql version.
-W
--password
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.
-x
--expanded
Turns on extended row format mode. This is equivalent to the command
\x.
-X,
--no-psqlrc
Do not read the start-up file ~/.psqlrc.
-?
--help
Shows help about psql command line arguments.
Long options are not available on all platforms.
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 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.
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 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 7.3rc2, 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 LISTEN [listen(5)] and NOTIFY [notify(5)].
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:
........
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.
Change the current working directory to directory. Without argument,
change to the current user's home directory.
Tip: 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.)
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.
Performs a frontend (client) copy. This is an operation that runs an
SQL COPY [copy(5)] 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.
Tip: 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: 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 -f option), and stdout refers to the query output stream (see
\o meta-command below).
Shows the copyright and distribution terms of PostgreSQL.
[ 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 equivalent to
\dtvs which will show a list of all tables, views, and sequences. This
is purely a convenience measure.
a [ 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.
d [ 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.
Note: PostgreSQL stores the object descriptions in the pg_description
system table.
D [ pattern ]
Lists all available domains (derived types). If pattern is specified,
only matching domains are shown.
f [ 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.
Note: To reduce clutter, \df does not show data type I/O functions.
This is implemented by ignoring functions that accept or return type
cstring.
istvS [ 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.
l This is an alias for \lo_list, which shows a list of large objects.
o [ pattern ]
Lists available operators with their operand and return types. If a
pattern is specified, only operators whose name matches the pattern
are listed.
p [ 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 grant(5) and revoke(5) are used to set access
permissions. See grant(5) for more information.
T [ pattern ]
Lists all data types or only those that match pattern. The command
form \dT+ shows extra information.
u [ pattern ]
Lists all database users, or only those that match pattern.
\dit (or \) [ 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.
Tip: 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.
\cho text [ ... ]
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.
Tip: If you use the \o command to redirect your query output you may
wish to use \qecho instead of this command.
\ncoding [ encoding ]
Sets the client encoding, if you are using multibyte encodings.
Without an argument, this command shows the current encoding.
[ 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.
p (or [ 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.
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.
96. br (or 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.
rt 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.
Note: See the description of the LO_TRANSACTION variable for important
information concerning all large object operations.
rt 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.
Note: See the description of the LO_TRANSACTION variable for important
information concerning all large object operations.
0. br Shows a list of all PostgreSQL ``large objects'' currently
stored in the database, along with any comments provided for them.
id Deletes the large object with OID loid from the database.
Tip: Use \lo_list to find out the large object's OID.
Note: See the description of the LO_TRANSACTION variable for important
information concerning all large object operations.
[ {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.
Tip: To intersperse text output in between query results, use \qecho.
Print
the current query buffer to the standard output.
set 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 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.
Note: 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
Toggles the 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.
In any case, psql 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 psql might not appear very discriminating about when to use
the pager.
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 Quit 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.
Resets (clears) the query buffer.
[ 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.
t [ 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.
Note: This command is totally separate from the SQL command SET
[set(5)].
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 options to be placed within the table tag in
HTML tabular output mode. This command is equivalent to \pset
tableattr table_options.
iming
Toggles a display of how long each SQL statement takes, in
milliseconds.
{filename | |command}
Outputs the current query buffer to the file filename or pipes it to
the Unix command command.
120. br Toggles extended row format mode. As such it is equivalent to
\pset expanded.
[ 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 grant(5) and revoke(5) are used to set access
permissions. See grant(5) 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 FEATURES
VARIABLES
psql 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
Note: 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 -a. If set to ``queries'',
psql merely prints all queries as they are sent to the backend. The
option 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. 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.
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.
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 -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 prompt psql issues is supposed to 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 set by the command line option -S. You can unset or
reset it at run time.
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.
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.
%n The 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 ``Variables
[psql(1)]'' 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.
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-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.)
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 disabled 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
o+ 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).
o+ The command-line history is stored in the file $HOME/.psql_history.
NOTES
o+ 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.
o+ 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.
o+ 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
Note: 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
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