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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 || _XOPEN_SOURCE

DESCRIPTION
       The clearenv() function clears the environment of all name-value pairs and sets the value of the external vari-
       able environ to NULL.

RETURN VALUE
       The clearenv() function returns zero on success, and a non-zero 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 stan-
       dard (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 3.22 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                             2007-07-26                       CLEARENV(3)