Section: POSIX Programmer's Manual (1P)
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.
--- null utility
This utility shall only expand command
It is used when a command is needed, as in the
condition of an
command, but nothing is to be done by the command.
See the DESCRIPTION.
The standard error shall be used only for diagnostic messages.
CONSEQUENCES OF ERRORS
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:
x=y : > z
which sets variable
to the value
(so that it persists after the null utility completes) and creates or
, Special Built-In Utilities
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
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