CLEARENV(3)                                                                           CLEARENV(3)



NAME
       clearenv - clear the environment

SYNOPSIS
       #include 

       int clearenv(void);

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 non-zero value on failure.


AVAILABILITY
       Not in libc4, libc5. In glibc since glibc 2.0.


CONFORMING TO
       Various  Unix  variants  (DGUX,  HPUX,  QNX,  ...).   POSIX.9  (bindings  for  FORTRAN77).
       POSIX.1-1996  did  not  accept clearenv() and putenv(), but changed its mind and scheduled
       these functions for some later issue of this standard (cf. B.4.6.1). However,  SUSv3  only
       adds putenv(), and rejected clearenv().


NOTES
       Used in security-conscious applications. If it is unavailable the assignment
                   environ = NULL;
       will probably do.

       The DGUX and Tru64 manpages write: If environ has been modified by anything other than the
       putenv(), getenv(), 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(5)




Linux Programmer's Manual                   2001-10-17                                CLEARENV(3)