clearenv - clear the environment
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
clearenv(): _SVID_SOURCE || _XOPEN_SOURCE
The clearenv() function clears the environment of all name-value pairs
and sets the value of the external variable environ to NULL.
The clearenv() function returns zero on success, and a nonzero value on
Not in libc4, libc5. In glibc since glibc 2.0.
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 only adds
putenv(3), and rejected clearenv().
Used in security-conscious applications. If it is unavailable the
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
getenv(3), putenv(3), setenv(3), unsetenv(3), environ(7)
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