linux man page for colon

COLON(P)						     POSIX Programmer's Manual							  COLON(P)

NAME
       colon - null utility

SYNOPSIS
       : [argument ...]

DESCRIPTION
       This utility shall only expand command arguments. It is used when a command is needed, as in the then condition of an if command, but noth-
       ing 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.

       The following sections are informative.

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
       Special Built-In Utilities

COPYRIGHT
       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technol-
       ogy -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
       Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and  the  original  IEEE
       and  The  Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained
       online at http://www.opengroup.org/unix/online.html .

IEEE
/The Open Group						       2003								  COLON(P)