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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.

       If the application modifies environ or the pointers to which it points, the  behavior  of  unsetenv()  is
       undefined.  The unsetenv() function shall update the list of pointers to which environ points.

       The  unsetenv()  function  need  not be reentrant. A function that is not required to be reentrant is not
       required to 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 is a null pointer, 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  IEEE Std 1003.1-2001,  <stdlib.h>,  <sys/types.h>,
       <unistd.h>


       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition,
       Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open  Group  Base
       Specifications Issue 6, Copyright (C) 2001-2003 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 .