colon(1p) — Linux manual page

COLON(1P)               POSIX Programmer's Manual               COLON(1P)

PROLOG         top

       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.

NAME         top

       colon — null utility

SYNOPSIS         top

       : [argument...]

DESCRIPTION         top

       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.

OPTIONS         top

       None.

OPERANDS         top

       See the DESCRIPTION.

STDIN         top

       Not used.

INPUT FILES         top

       None.

ENVIRONMENT VARIABLES         top

       None.

ASYNCHRONOUS EVENTS         top

       Default.

STDOUT         top

       Not used.

STDERR         top

       The standard error shall be used only for diagnostic messages.

OUTPUT FILES         top

       None.

EXTENDED DESCRIPTION         top

       None.

EXIT STATUS         top

       Zero.

CONSEQUENCES OF ERRORS         top

       Default.

       The following sections are informative.

APPLICATION USAGE         top

       None.

EXAMPLES         top

       : ${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         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       Section 2.14, Special Built-In Utilities

COPYRIGHT         top

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 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 .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                2017                         COLON(1P)

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