clearenv(3) -- Linux man page
NAMEclearenv - clear the environment
#include <stdlib.h> int clearenv(void);
DESCRIPTIONThe clearenv() function clears the environment of all name-value pairs and sets the value of the external variable environ to NULL.
RETURN VALUEThe clearenv() function returns zero on success, and a non-zero value on failure.
AVAILABILITYNot in libc4, libc5. In glibc since glibc 2.0.
CONFORMING TOVarious 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().
NOTESUsed in security-conscious applications. If it is unavailable the assignment
environ = NULL;
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.
SEE ALSOgetenv(3), putenv(3), setenv(3), unsetenv(3), environ(5)