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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.
       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 .

IEEE/The Open Group                  2003                         UNSETENV(3P)