unsetenv(3p) - phpMan

UNSETENV(P)                                                        UNSETENV(P)



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 â€â€™=â€â€™ 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 behav-
       ior 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 â€â€™=â€â€™ 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 .



POSIX                                2003                          UNSETENV(P)

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