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UNSETENV(3P)               POSIX Programmer's Manual              UNSETENV(3P)
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 success-
       fully.
       The unsetenv() function shall update the list of pointers to which env-
       iron 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 Electri-
       cal 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.ker-
       nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group                  2013                         UNSETENV(3P)