Section: POSIX Programmer's Manual (3P)
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.
--- remove an environment variable
int unsetenv(const char *name);
function shall remove an environment variable from the environment
of the calling process. The
argument points to a string, which is the name of the variable to be
removed. The named argument shall not contain an
character. If the named variable does not exist in the current
environment, the environment shall be unchanged and the function is
considered to have completed successfully.
function shall update the list of pointers to which
function need not be thread-safe.
Upon successful completion, zero shall be returned. Otherwise, -1
shall be returned,
set to indicate the error, and the environment shall be unchanged.
function shall fail if:
argument points to an empty string, or points to a
string containing an
The following sections are informative.
Refer to the RATIONALE section in
The Base Definitions volume of POSIX.1-2017,
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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