unsetenv(3p) — Linux manual page

UNSETENV(3P)            POSIX Programmer's Manual           UNSETENV(3P)

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

       unsetenv — remove an environment variable

SYNOPSIS         top

       #include <stdlib.h>

       int unsetenv(const char *name);

DESCRIPTION         top

       The unsetenv() function shall remove an environment variable from
       the environment of the calling process. The name 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.

       The unsetenv() function shall update the list of pointers to
       which environ points.

       The unsetenv() function need not be thread-safe.

RETURN VALUE         top

       Upon successful completion, zero shall be returned. Otherwise, -1
       shall be returned, errno set to indicate the error, and the
       environment shall be unchanged.

ERRORS         top

       The unsetenv() function shall fail if:

       EINVAL The name argument points to an empty string, or points to
              a string containing an '=' character.

       The following sections are informative.

EXAMPLES         top

       None.

APPLICATION USAGE         top

       None.

RATIONALE         top

       Refer to the RATIONALE section in setenv(3p).

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       getenv(3p), setenv(3p)

       The Base Definitions volume of POSIX.1‐2017, stdlib.h(0p),
       sys_types.h(0p)

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                      UNSETENV(3P)

Pages that refer to this page: stdlib.h(0p),  getenv(3p),  setenv(3p)

HTML rendering created 2024-06-26 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH.