NAME
colon — null
utility
SYNOPSIS
DESCRIPTION
This utility shall only expand command argument s. It is used when a command is needed, as in the then condition of an if command, but nothing is to be done by the command.
OPTIONS
None.
OPERANDS
See the DESCRIPTION.
STDIN
Not used.
INPUT FILES
None.
ENVIRONMENT VARIABLES
None.
ASYNCHRONOUS EVENTS
Default.
STDOUT
Not used.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
None.
EXTENDED DESCRIPTION
None.
EXIT STATUS
Zero.
CONSEQUENCES OF ERRORS
Default.
APPLICATION USAGE
None.
EXAMPLES
: ${X=abc}
if false
then :
else echo $X
fi
abc
As with any of the special built-ins, the null utility can also have variable assignments and redirections associated with it, such as:
x=y : > z
which sets variable x to the value y (so that it persists after the null utility completes) and creates or truncates file z.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSO
CHANGE HISTORY
Issue 6
IEEE Std 1003.1-2001 (“POSIX.1”)/Cor 1-2002, item XCU/TC1/D6/5 is applied so that the reference page sections use terms as described in the Utility Description Defaults ( xcu_chap01(1) ). No change in behavior is intended.
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