2004-11-03 13:51:07 +00:00
|
|
|
.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved
|
2007-06-20 22:33:04 +00:00
|
|
|
.TH "COLON" 1P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
|
2004-11-03 13:51:07 +00:00
|
|
|
.\" colon
|
2007-09-20 06:03:25 +00:00
|
|
|
.SH 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.
|
2004-11-03 13:51:07 +00:00
|
|
|
.SH NAME
|
|
|
|
colon \- null utility
|
|
|
|
.SH SYNOPSIS
|
|
|
|
.LP
|
|
|
|
\fB:\fP \fB[\fP\fIargument\fP \fB...\fP\fB]\fP
|
|
|
|
.SH DESCRIPTION
|
|
|
|
.LP
|
|
|
|
This utility shall only expand command \fIargument\fPs. It is used
|
|
|
|
when a command is needed, as in the \fBthen\fP condition of
|
|
|
|
an \fBif\fP command, but nothing is to be done by the command.
|
|
|
|
.SH OPTIONS
|
|
|
|
.LP
|
|
|
|
None.
|
|
|
|
.SH OPERANDS
|
|
|
|
.LP
|
|
|
|
See the DESCRIPTION.
|
|
|
|
.SH STDIN
|
|
|
|
.LP
|
|
|
|
Not used.
|
|
|
|
.SH INPUT FILES
|
|
|
|
.LP
|
|
|
|
None.
|
|
|
|
.SH ENVIRONMENT VARIABLES
|
|
|
|
.LP
|
|
|
|
None.
|
|
|
|
.SH ASYNCHRONOUS EVENTS
|
|
|
|
.LP
|
|
|
|
Default.
|
|
|
|
.SH STDOUT
|
|
|
|
.LP
|
|
|
|
Not used.
|
|
|
|
.SH STDERR
|
|
|
|
.LP
|
|
|
|
The standard error shall be used only for diagnostic messages.
|
|
|
|
.SH OUTPUT FILES
|
|
|
|
.LP
|
|
|
|
None.
|
|
|
|
.SH EXTENDED DESCRIPTION
|
|
|
|
.LP
|
|
|
|
None.
|
|
|
|
.SH EXIT STATUS
|
|
|
|
.LP
|
|
|
|
Zero.
|
|
|
|
.SH CONSEQUENCES OF ERRORS
|
|
|
|
.LP
|
|
|
|
Default.
|
|
|
|
.LP
|
|
|
|
\fIThe following sections are informative.\fP
|
|
|
|
.SH APPLICATION USAGE
|
|
|
|
.LP
|
|
|
|
None.
|
|
|
|
.SH EXAMPLES
|
|
|
|
.sp
|
|
|
|
.RS
|
|
|
|
.nf
|
|
|
|
|
|
|
|
\fB: ${X=abc}
|
|
|
|
if false
|
|
|
|
then :
|
|
|
|
else echo $X
|
|
|
|
fi
|
|
|
|
\fP\fBabc\fP
|
|
|
|
.fi
|
|
|
|
.RE
|
|
|
|
.LP
|
|
|
|
As with any of the special built-ins, the null utility can also have
|
|
|
|
variable assignments and redirections associated with it,
|
|
|
|
such as:
|
|
|
|
.sp
|
|
|
|
.RS
|
|
|
|
.nf
|
|
|
|
|
|
|
|
\fBx=y : > z
|
|
|
|
\fP
|
|
|
|
.fi
|
|
|
|
.RE
|
|
|
|
.LP
|
|
|
|
which sets variable \fIx\fP to the value \fIy\fP (so that it persists
|
|
|
|
after the null utility completes) and creates or
|
|
|
|
truncates file \fBz\fP.
|
|
|
|
.SH RATIONALE
|
|
|
|
.LP
|
|
|
|
None.
|
|
|
|
.SH FUTURE DIRECTIONS
|
|
|
|
.LP
|
|
|
|
None.
|
|
|
|
.SH SEE ALSO
|
|
|
|
.LP
|
|
|
|
\fISpecial Built-In Utilities\fP
|
|
|
|
.SH COPYRIGHT
|
|
|
|
Portions of this text are reprinted and reproduced in electronic form
|
|
|
|
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
|
|
|
|
-- 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 .
|