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.
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.
The standard error shall be used only for diagnostic messages.
The following sections are informative.
else echo $X
As with any of the special built-ins, the null utility can also
have variable assignments and redirections associated with it, such as:
which sets variable x to the value y (so that it
persists after the null utility completes) and creates or truncates file
Section 2.14, Special Built-In Utilities
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
7, Copyright (C) 2013 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013
Technical Corrigendum 1 applied.) 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.unix.org/online.html .
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