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.

SEE ALSO

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

COLOPHON

       This  page  is  part of release 4.04 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/.