PSQL(1) PostgreSQL Client Applications PSQL(1)NAME
psql - Postgres interactive terminal
SYNOPSIS
psql [ options ] [ dbname [ user ] ]
SUMMARY
psql is a terminal-based front-end to Postgres. It enables you to type
in queries interactively, issue them to Postgres, and see the query
results. Alternatively, input can be from a file. In addition, it pro‐
vides a number of meta-commands and various shell-like features to
facilitate writing scripts and automating a wide variety of tasks.
DESCRIPTION
CONNECTING TO A DATABASE
psql is a regular Postgres 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 con‐
nect 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 username, as
is the default database name. Note that you can't just connect to any
database under any username. Your database administrator should have
informed you about your access rights. To save you some typing you can
also set the environment variables 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 data‐
base to which psql is currently connected, followed by the string "=>".
For example,
$ psql testdb
Welcome to psql, the PostgreSQL interactive terminal.
Type: \copyright for distribution terms
\h for help with SQL commands
\? for help on internal slash commands
\g or terminate with semicolon to execute query
\q to quit
testdb=>
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 with‐
out error, the query results are displayed on the screen.
Whenever a query is executed, psql also polls for asynchronous notifi‐
cation events generated by LISTEN [listen(l)] and NOTIFY [notify(l)].
PSQL META-COMMANDS
Anything you enter in psql that begins with an unquoted backslash is a
psql meta-command that is processed by psql itself. These commands are
what makes psql interesting for administration or scripting. Meta-com‐
mands are more commonly called slash or backslash commands.
The format of a psql command is the backslash, followed immediately by
a command verb, then any arguments. The arguments are separated from
the command verb and each other by any number of whitespace characters.
To include whitespace into an argument you must 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 hexadec‐
imal code).
If an unquoted argument begins with a colon (:), it is taken as a vari‐
able and the value of the variable is taken as the argument instead.
Arguments that are quoted in ``backticks'' (`) are taken as a command
line that is passed to the shell. The output of the command (with a
trailing newline removed) is taken as the argument value. The above
escape sequences also apply in backticks.
Some commands take the name of 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. For all other commands double quotes are not special and will
become part of 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-com‐
mand cannot continue beyond the end of the line.
The following meta-commands are defined:
\a If the current table output format is unaligned, switch to
aligned. If it is not unaligned, set it to unaligned. This com‐
mand is kept for backwards compatibility. See \pset for a gen‐
eral solution.
\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 username, access denied,
etc.), the previous connection will be kept if and only if psql
is in interactive mode. When executing a non-interactive script,
processing will immediately stop with an error. This distinction
was chosen as a user convenience against typos on the one hand,
and a safety mechanism that scripts are not accidentally acting
on the wrong database on the other hand.
\copy table
Performs a frontend (client) copy. This is an operation that
runs an SQL COPY [copy(l)] command, but instead of the backend's
reading or writing the specified file, and consequently requir‐
ing backend access and special user privilege, as well as being
bound to the file system accessible by the backend, psql reads
or writes the file and routes the data between the backend and
the local file system.
The syntax of the command is similar to that of the SQL COPY
command (see its description for the details). Note that,
because of this, special parsing rules apply to the \copy com‐
mand. In particular, the variable substitution rules and back‐
slash escapes do not apply.
Tip: This operation is not as efficient as the SQL COPY command
because all data must pass through the client/server 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).
\copyright
Shows the copyright and distribution terms of Postgres.
\d relation
Shows all columns of relation (which could be a table, view,
index, or sequence), their types, and any special attributes
such as NOT NULL or defaults, if any. If the relation is, in
fact, a table, any defined indices are also listed. If the
relation is a view, the view definition is also shown.
The command form \d+ is identical, but any comments associated
with the table columns are shown as well.
Note: If \d is called without any arguments, 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 [ object ]
Shows the descriptions of object (which can be a regular expres‐
sion), or of all objects if no argument is given. (``Object''
covers aggregates, functions, operators, types, relations
(tables, views, indices, sequences, large objects), rules, and
triggers.) For example:
=> \dd version
Object descriptions
Name | What | Description
---------+----------+---------------------------
version | function | PostgreSQL version string
(1 row)
Descriptions for objects can be generated with the COMMENT ON
SQL command.
Note: Postgres stores the object descriptions in the pg_descrip‐
tion system table.
\df [ pattern ]
Lists available functions, together with their argument and
return types. If pattern (a regular expression) is specified,
only matching functions are shown. If the form \df+ is used,
additional information about each function, including language
and description, is shown.
\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 them in any order to
obtain a listing of them, together with who the owner is.
If pattern is specified, it is a regular expression that
restricts the listing to those objects whose name matches. If
one appends a ``+'' to the command name, each object is listed
with its associated description, if any.
\dl This is an alias for \lo_list, which shows a list of large
objects.
\do [ name ]
Lists available operators with their operand and return types.
If name is specified, only operators with that name will be
shown.
\dp [ pattern ]
This is an alias for \z which was included for its greater
mnemonic value (``display permissions'').
\dT [ pattern ]
Lists all data types or only those that match pattern. The com‐
mand form \dT+ shows extra information.
\edit (or \e) [ filename ]
If filename is specified, the file is edited; after the editor
exits, its content is copied back to the query buffer. If no
argument is given, the current query buffer is copied to a tem‐
porary file which is then edited in the same fashion.
The new query buffer is then re-parsed according to the normal
rules of psql, where the whole buffer is treated as a single
line. (Thus you cannot make scripts this way. Use \i for that.)
This means also that if the query ends with (or rather 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, EDI‐
TOR, and VISUAL (in that order) for an editor to use. If all of
them are unset, /bin/vi is run.
\echo text [ ... ]
Prints the arguments to the standard output, separated by one
space and followed by a newline. This can be useful to inter‐
sperse information in the output of scripts. For example:
=> \echo `date`
Tue Oct 26 21:40:57 CEST 1999
If the first argument is an unquoted -n the the trailing 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 multibyte encodings.
Without an argument, this command shows the current encoding.
\f [ string ]
Sets the field separator for unaligned query output. The default
is pipe (|). See also \pset for a generic way of setting output
options.
\g [ { filename | |command } ]
Sends the current query input buffer to the backend and option‐
ally saves the output in filename or pipes the output into a
separate Unix shell to execute command. A bare \g is virtually
equivalent to a semicolon. A \g with argument is a ``one-shot''
alternative to the \o command.
\help (or \h) [ command ]
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.
\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 Postgres installation was com‐
piled 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 Postgres ``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.
\lo_list
Shows a list of all Postgres ``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 std‐
out.
``Query results'' includes all tables, command responses, and
notices obtained from the database server, as well as output of
various backslash commands that query the database (such as \d),
but not error messages.
Tip: To intersperse text output in between query results, use
\qecho.
\p Print the current query buffer to the standard output.
\pset parameter [ value ]
This command sets options affecting the output of query result
tables. parameter describes which option is to be set. The
semantics of value depend thereon.
Adjustable printing options are:
format Sets the output format to one of unaligned, aligned,
html, or latex. Unique abbreviations are allowed. (That
would mean one letter is enough.)
``Unaligned'' writes all 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-sepa‐
rated). ``Aligned'' mode is the standard, human-read‐
able, nicely formatted text output that is default. The
``HTML'' and ``LaTeX'' modes put out tables that are
intended to be included in documents using the 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 bor‐
der=... attribute, in the others only values 0 (no bor‐
der), 1 (internal dividing lines), and 2 (table frame)
make sense.
expanded (or x)
Toggles between regular and expanded format. When
expanded format is enabled, all output has two columns
with the 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).
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 dis‐
play may show extra information such as column headers,
titles, and various footers. In tuples only mode, only
actual table data is shown.
title [ text ]
Sets the table title for any subsequently printed tables.
This can be used to give your output descriptive tags. If
no argument is given, the title is unset.
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 list of a pager to do table output. If the
environment variable PAGER is set, the output is piped to
the specified program. Otherwise more is used.
In any case, psql only uses the pager if it seems appro‐
priate. 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 and when not to.
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.
\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: As of psql version 7.0 it is no longer necessary to save
the command history, since that will be done automatically on
program termination. The history is also loaded automatically
every time psql starts up.
\set [ name [ value [ ... ]]]
Sets the internal variable name to value or, if more than one
value is given, to the concatenation of all of them. If no sec‐
ond argument is given, the variable is just set with no value.
To unset a variable, use the \unset command.
Valid variable names can contain characters, digits, and under‐
scores. See the section 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 docu‐
mented 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.
\w {filename | |command}
Outputs the current query buffer to the file filename or pipes
it to the Unix command command.
\x Toggles extended row format mode. As such it is equivalent to
\pset expanded.
\z [ pattern ]
Produces a list of all tables in the database with their appro‐
priate access permissions listed. If an argument is given it is
taken as a regular expression which limits the listing to those
tables which match it.
test=> \z
Access permissions for database "test"
Relation | Access permissions
----------+-------------------------------------
my_table | {"=r","joe=arwR", "group staff=ar"}
(1 row )
Read this as follows:
· "=r": PUBLIC has read (SELECT) permission on the table.
· "joe=arwR": User joe has read, write (UPDATE, DELETE),
``append'' (INSERT) permissions, and permission to create
rules on the table.
· "group staff=ar": Group staff has SELECT and INSERT permis‐
sion.
The commands GRANT [grant(l)] and REVOKE [revoke(l)] are used to set
access 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.
COMMAND-LINE OPTIONS
If so configured, psql understands both standard Unix short options,
and GNU-style long options. The latter are not available on all sys‐
tems.
-a, --echo-all
Print all the lines to the screen as they are read. This is more
useful for script processing rather than interactive mode. This
is equivalent to setting the variable ECHO to all.
-A, --no-align
Switches to unaligned output mode. (The default output mode is
otherwise aligned.)
-c, --command 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 parseable
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
Specifies the name of the database to connect to. This is equiv‐
alent 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 equiva‐
lent 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 func‐
tionality into your own programs. This is equivalent to setting
the variable ECHO_HIDDEN from within psql.
-f, --file filename
Use the file filename as the source of queries instead of read‐
ing queries interactively. After the file is processed, psql
terminates. This is in many ways equivalent to the internal
command \i.
Using this option is subtly different from writing psql < file‐
name. In general, both will do what you expect, but using -f
enables some nice features such as error messages with line num‐
bers. 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, --field-separator separator
Use separator as the field separator. This is equivalent to
\pset fieldsep or \f.
-h, --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, --output filename
Put all query output into file filename. This is equivalent to
the command \o.
-p, --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, --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 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, --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-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 connect‐
ing to the database.
This option is deprecated, as it is conceptually flawed.
(Prompting for a non-default user name and prompting for a pass‐
word 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
Connects to the database as the user username instead of the
default. (You must have permission to do so, of course.)
-v, --variable, --set 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 connect‐
ing to a database. This will remain set for the entire session,
even if you change the database connection with the meta-command
\connect.
As of version 7.0, 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 pass‐
word 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.
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 argu‐
ment 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 runtime by altering the value of the
variable or represent some state of the application. Although you can
use these variables for any other purpose, this is not recommended, as
the program behavior might grow really strange really quickly. By con‐
vention, all specially treated variables consist of all upper-case let‐
ters (and possibly numbers and underscores). To ensure maximum compati‐
bility 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 writ‐
ten 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
Postgres 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 Postgres 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 unpre‐
dictable (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 pro‐
cessing 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 pro‐
gram 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 substi‐
tute (``interpolate'') them into regular SQL statements. The syntax for
this is again to prepend the variable name with a colon (:).
testdb=> \set foo 'my_table'
testdb=> SELECT * FROM :foo;
would then query the table my_table. The value of the variable is
copied literally, so it can even contain unbalanced quotes or 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 con‐
tain 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 inter‐
pretations. 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 syn‐
tax for array slices and type casts are Postgres 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 sub‐
stitutions are:
%M The full hostname (with domain name) of the database server (or
``localhost'' if hostname information is not available).
%m The hostname of the database server, truncated after the first
dot.
%> The port number at which the database server is listening.
%n The username 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 ``#'', oth‐
erwise 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 /* ... */ com‐
ment, 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 inter‐
preted as a hexadecimal digit and the character with the corre‐
sponding code is substituted. If the first digit is 0 the char‐
acters 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 ``Vari‐
ables [psql(1)]'' for details.
%`command`
The output of command, similar to ordinary ``back-tick'' substi‐
tution.
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.
MISCELLANEOUS
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.
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).
GNU READLINE
psql supports the readline and history libraries 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 automati‐
cally 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.)
If you have the readline library installed but psql does not seem to
use it, you must make sure that Postgres's top-level configure script
finds it. configure needs to find both the library libreadline.a (or a
shared library equivalent) and the header files readline.h and his‐
tory.h (or readline/readline.h and readline/history.h) in appropriate
directories. If you have the library and header files installed in an
obscure place you must tell configure about them, for example:
$ ./configure --with-includes=/opt/gnu/include --with-libs=/opt/gnu/lib ...
Then you have to recompile psql (not necessarily the entire code tree).
The GNU readline library can be obtained from the GNU project's FTP
server at ftp://ftp.gnu.org <URL:ftp://ftp.gnu.org>.
EXAMPLES
Note: This section only shows a few examples specific to psql.
If you want to learn SQL or get familiar with Postgres, you
might wish to read the Tutorial that is included in the distri‐
bution.
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 inter‐
esting:
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
APPENDIX
BUGS AND ISSUES
· In some earlier life psql allowed the first argument to start
directly after the (single-letter) command. For compatibility this is
still supported to some extent but I am not going to explain the
details here as this use is discouraged. But if you get strange mes‐
sages, keep this in mind. For example
testdb=> \foo
Field separator is "oo",
which is perhaps not what one would expect.
· psql only works smoothly with servers of the same version. That does
not mean other combinations will fail outright, but subtle and not-
so-subtle problems might come up.
· 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 ``PQexec: you gotta get out of a COPY state yourself'', simply
reset the connection by entering \c - -.
Application 2000-12-25 PSQL(1)