CLEARENV(3) Linux Programmer's Manual CLEARENV(3)
clearenv - clear the environment
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
clearenv(): _SVID_SOURCE || _BSD_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 failure.
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 adds only putenv(3), and rejected clearenv().
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.
getenv(3), putenv(3), setenv(3), unsetenv(3), environ(7)
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Linux 2010-10-04 CLEARENV(3)