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



PROLOG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NAME
       unsetenv -- remove an environment variable

SYNOPSIS
       #include <stdlib.h>

       int unsetenv(const char *name);

DESCRIPTION
       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
       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
       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
       None.

APPLICATION USAGE
       None.

RATIONALE
       Refer to the RATIONALE section in setenv().

FUTURE DIRECTIONS
       None.

SEE ALSO
       getenv(), setenv()

       The Base Definitions volume of POSIX.1-2017, <stdlib.h>, <sys_types.h>

COPYRIGHT
       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(3)
