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clearenv - clear the environment
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 non-zero value on failure.
Not in libc4, libc5. In glibc since glibc 2.0.
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().
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.
getenv(3), putenv(3), setenv(3), unsetenv(3), environ(5)
Linux Programmer's Manual 2001-10-17 CLEARENV(3)
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