redhat man page for clearenv

CLEARENV(3)						     Library Functions Manual						       CLEARENV(3)

NAME
       clearenv - clear the environment

SYNOPSIS
       #include <stdlib.h>

       int clearenv(void);

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 non-zero value on failure.

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

CONFORMING TO
       Various	Unix variants (DGUX, HPUX, QNX, ...).  POSIX.9 (bindings for FORTRAN77).  POSIX.1-1996 did not accept clearenv() and putenv(), but
       changed its mind and scheduled these functions for some later issue of this standard (cf. B.4.6.1). However, SUSv3 only adds putenv(),  and
       rejected clearenv().

NOTES
       Used in security-conscious applications. If it is unavailable the assignment
		   environ = NULL;
       will probably do.

       The  DGUX  and  Tru64  manpages write: If environ has been modified by anything other than the putenv(), getenv(), 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(5)

Linux Programmer's Manual					    2001-10-17							       CLEARENV(3)