This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       None.

       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(3POSIX)

       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.

       The unsetenv() function shall fail if:

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

       Thefollowingsectionsareinformative.

       None.

       None.

       unsetenv — remove an environment variable

       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.

       Refer to the RATIONALE section in setenv().

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

getenv(), setenv()

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

       #include <stdlib.h>

       int unsetenv(const char *name);