clearenv - phpMan

CLEARENV(3)                                                        CLEARENV(3)



NAME
       clearenv - clear the environment

SYNOPSIS
       #include <stdlib.h>

       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). How-
       ever, 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)

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