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 (DG/UX, HP-UX, 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, POSIX.1-2001 only adds putenv(), 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 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(7)

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