PSQL(1) PostgreSQL Client Applications PSQL(1)NAMEpsql - PostgreSQL interactive terminal
SYNOPSISpsql [ options ] [ dbname [ user ] ]
DESCRIPTIONpsql 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 num-
ber 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 set-
ting 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 com-
pletely parsable by the backend (i.e., it contains
no psql specific features), or it is a single back-
slash 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 pro-
grams. 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.
-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 pur-
poses 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 pass-
word 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 con-
nection attempt will fail.
-x
--expanded
Turns on extended row format mode. This is equiva-
lent 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 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.
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 inter-
preted 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 con-
nect 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 envi-
ronment 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, fol-
lowed 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. Ordinar-
ily, input lines are sent to the backend when a query-ter-
minating 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 asyn-
chronous notification events generated by LISTEN [lis-
ten(l)] and NOTIFY [notify(l)].
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 com-
monly 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 substi-
tutions 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 dou-
ble quotes is coerced to lower-case, while whitespace
within double quotes is included in the argument.
Parsing for arguments stops when another unquoted back-
slash 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.
\cd [directory]
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.)
\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 distinc-
tion was chosen as a user convenience against typos
on the one hand, and a safety mechanism that
scripts are not accidentally acting on the wrong
database on the other hand.
\copy table
Performs a frontend (client) copy. This is an oper-
ation that runs an SQL COPY [copy(l)] 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 pars-
ing rules apply to the \copy command. In particu-
lar, 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 prefer-
able.
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).
\copyright
Shows the copyright and distribution terms of Post-
greSQL.
\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, con-
straints, 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.
\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 pat-
tern, or of all visible objects if no argument is
given. But in either case, only objects that have a
description are listed. (``Object'' covers aggre-
gates, 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.
\dD [ pattern ]
Lists all available domains (derived types). If
pattern is specified, only matching domains are
shown.
\df [ pattern ]
Lists available functions, together with their
argument and return types. If pattern is specified,
only matching functions are shown. If the form \df+
is used, additional information about each func-
tion, 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.
\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 pat-
tern are listed.
The commands grant(l) and revoke(l) are used to set
access permissions. See grant(l) for more informa-
tion.
\dT [ pattern ]
Lists all data types or only those that match pat-
tern. The command form \dT+ shows extra informa-
tion.
\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.
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.
\echo text [ ... ]
Prints the arguments to the standard output, sepa-
rated 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.
\encoding [ encoding ]
Sets the client encoding, if you are using multi-
byte encodings. Without an argument, this command
shows the current encoding.
\f [ string ]
Sets the field separator for unaligned query out-
put. 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 exe-
cute 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.
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 for-
mat is already on, it is switched back to the
default aligned text format. This command is for
compatibility and convenience, but see \pset about
setting other output options.
\i filename
Reads input from the file filename and executes it
as though it had been typed on the keyboard.
Note: If you want to see the lines on the screen as
they are read you must set the variable ECHO to
all.
\l (or \list)
List 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_export loid filename
Reads the large object with OID loid from the
database and writes it to filename. Note that this
is subtly different from the server function
lo_export, which acts with the permissions of the
user that the database server runs as and on the
server's file system.
Tip: Use \lo_list to find out the large object's
OID.
Note: See the description of the LO_TRANSACTION
variable for important information concerning all
large object operations.
\lo_import filename [ comment ]
Stores the file into a PostgreSQL ``large object''.
Optionally, it associates the given comment with
the object. Example:
foo=> \lo_import '/home/peter/pictures/photo.xcf' 'a picture of me'
lo_import 152801
The response indicates that the large object
received object id 152801 which one ought to remem-
ber if one wants to access the object ever again.
For that reason it is recommended to always associ-
ate 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.
\lo_list
Shows a list of all PostgreSQL ``large objects''
currently stored in the database, along with any
comments provided for them.
\lo_unlink loid
Deletes the large object with OID loid from the
database.
Tip: Use \lo_list to find out the large object's
OID.
Note: 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 com-
mands that query the database (such as \d), but not
error messages.
Tip: To intersperse text output in between query
results, use \qecho.
\p Print the current query buffer to the standard out-
put.
\pset parameter [ value ]
This command sets options affecting the output of
query result tables. parameter describes which
option is to be set. The semantics of value depend
thereon.
Adjustable printing options are:
format Sets the output format to one of unaligned,
aligned, html, or latex. Unique abbrevia-
tions 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-sep-
arated). ``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 doc-
uments! (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 bor-
ders 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 out-
put 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 cre-
ate, 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 dis-
play. Full display may show extra informa-
tion 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 bor-
der 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 vari-
able 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 argu-
ments. In the future this call might show the cur-
rent 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.
\r Resets (clears) the query buffer.
\s [ filename ]
Print or save the command line history to filename.
If filename is omitted, the history is written to
the standard output. This option is only available
if psql is configured to use the GNU history
library.
Note: In the current version, it is no longer nec-
essary 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, dig-
its, 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(l)].
\t Toggles the display of output column name headings
and row count footer. This command is equivalent to
\pset tuples_only and is provided for convenience.
\T table_options
Allows you to specify 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 file-
name 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 pat-
tern are listed.
The commands grant(l) and revoke(l) are used to set
access permissions. See grant(l) for more informa-
tion.
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 incorpora-
tion 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 exam-
ple [0-9] to match ``any digit''. To make any of these
pattern-matching characters be interpreted literally, sur-
round it with double quotes.
A pattern that contains an (unquoted) dot is interpreted
as a schema name pattern followed by an object name pat-
tern. 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 com-
mand:
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 ``vari-
able 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 com-
patibility in the future, avoid such variables. A list of
all specially treated variables follows.
DBNAME The name of the database you are currently con-
nected 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 vari-
able 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 match-
ing 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 his-
tory. The default value is 500.
Note: This feature was shamelessly plagiarized from
bash.
HOST The database server host you are currently con-
nected 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 Con-
trol+D) to an interactive session of psql will ter-
minate 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 trans-
action 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 some-
times 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 ses-
sion 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 sup-
posed 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 inter-
active 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 inter-
polation 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 for-
eign 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 pro-
gram 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 stan-
dard SQL for embedded query languages, such as ecpg. The
colon syntax for array slices and type casts are Post-
greSQL extensions, hence the conflict.)
PROMPTING
The prompts psql issues can be customized to your prefer-
ence. 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 encoun-
tered. 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 substi-
tuted. If the first digit is 0 the characters are
interpreted as on octal number and the correspond-
ing character is substituted. Otherwise a decimal
number is assumed.
%:name:
The value of the psql, variable name. See the sec-
tion ``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 sup-
ported, 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 docu-
mentation 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 compat-
ibility 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 ver-
sion. 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 termi-
nated first'', simply reset the connection by entering
\c - -.
EXAMPLES
Note: This section only shows a few examples spe-
cific 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
Application 2002-11-22 PSQL(1)
