unsetenv

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



PROLOG
       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
       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.1‐2008, <stdlib.h>, <sys_types.h>

COPYRIGHT
       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 .

       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                   2013                      UNSETENV(3POSIX)