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>

COPYRIGHT

       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 .