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.1‐2017, <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 .