[Go to CFHT Home Page] Man Pages
Back to Software Index  BORDER=0Manpage Top Level
    CLEARENV(3) manual page Table of Contents

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.

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 3.78 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/.

Table of Contents