colon man page

Prolog

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ (consult the corresponding Linux manual page for details of Linux behavior), or the interface may not be implemented on Linux.

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 nothing is to be done by the command.

Operands

See the Description.

Stdin

Not used.

Asynchronous Events

Default.

Stdout

Not used.

Stderr

The standard error shall be used only for diagnostic messages.

Exit Status

Zero.

Consequences of Errors

Default.

The following sections are informative.

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.

See Also

Section 2.14, Special Built-In Utilities

Info

2013 IEEE/The Open Group POSIX Programmer's Manual