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 variable envi-
       ron 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 3.25 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/.



Linux                                                      2007-07-26                                                CLEARENV(3)