MPE/iX Shell and Utilities Reference Manual, Vol 1

colon(1) MPE/iX Shell and Utilities colon(1)

NAME

: (colon) — do nothing, successfully

SYNOPSIS

: [argument ...]

DESCRIPTION

The : (colon) command simply yields an exit status of zero (success). This can be surpris-

ingly useful, for example, when you are evaluating shell expressions for their side effects.

EXAMPLES

: ${VAR:="default value"}

sets

VAR

to a default value if and only if it is not already set.

DIAGNOSTICS

Since this command always succeeds, the only possible exit status is:

0 Successful completion.

Messages

Because this utility is built into the

MPE/iX Shell, see the sh(1) man page for a complete list of

error messages that you may receive when using it.

PORTABILITY

POSIX.2. x/OPEN Portability Guide 4.0. All UNIX systems.

NOTE

This is a special built-in command of the shell.