CLEARENV(3)						     Linux Programmer's Manual						       CLEARENV(3)

NAME

       clearenv - clear the environment

SYNOPSIS

       #include <stdlib.h>

       int clearenv(void);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       clearenv(): _SVID_SOURCE || _XOPEN_SOURCE

DESCRIPTION

       The clearenv() function clears the environment of all name-value pairs and sets the value of the external variable environ to NULL.

RETURN VALUE

       The clearenv() function returns zero on success, and a nonzero value on failure.

VERSIONS

       Not in libc4, libc5.  In glibc since glibc 2.0.

CONFORMING TO

       Various	Unix  variants (DG/UX, HP-UX, QNX, ...).  POSIX.9 (bindings for FORTRAN77).  POSIX.1-1996 did not accept clearenv() and putenv(3),
       but changed its mind and scheduled these functions for some later issue of this standard (cf. B.4.6.1).	However,  POSIX.1-2001	only  adds
       putenv(3), and rejected clearenv().

NOTES

       Used in security-conscious applications.  If it is unavailable the assignment

	   environ = NULL;

       will probably do.

       The DG/UX and Tru64 man pages write: If environ has been modified by anything other than the putenv(3), getenv(3), or clearenv() functions,
       then clearenv() will return an error and the process environment will remain unchanged.

SEE ALSO

       getenv(3), putenv(3), setenv(3), unsetenv(3), environ(7)

COLOPHON

       This page is part of release 3.25 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2007-07-26							       CLEARENV(3)