CLEARENV

Section: Linux Programmer's Manual (3)
Updated: 2015-07-23
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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

Available since glibc 2.0.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).

Interface	Attribute	Value
clearenv()	Thread safety	MT-Unsafe const:env

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.

COLOPHON

This page is part of release 4.02 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/.