clearenv

       #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.

SEE ALSO
       getenv(3), putenv(3), setenv(3), unsetenv(3), environ(7)

COLOPHON
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