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 || _BSD_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 3.50 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/.