clearenv - clear the environment
The clearenv() function returns zero on success, and a nonzero value on failure.
Available 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 (see §B.4.6.1). However, POSIX.1-2001 adds only putenv(3), and rejected clearenv().
On systems where clearenv() is unavailable, the assignment
environ = NULL;
will probably do.
The clearenv() function may be useful in security-conscious applications that want to precisely control the environment that is passed to programs executed using exec(3). The application would do this by first clearing the environment and then adding select environment variables.
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.
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