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CentOS 7.0 - man page for clearenv (centos section 3)

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 || _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 adds only 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 3.53 of the Linux man-pages project. A description of the project, and informa- tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2010-10-04 CLEARENV(3)


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