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CLEARENV (3) | C library functions | Unix Manual Pages | :man

NAME

clearenv - clear the environment

CONTENTS

Synopsis
Description
Availability
Notes

SYNOPSIS



#include <stdlib.h>



"int clearenv(void);"

DESCRIPTION

The clearenv() function clears the environment of all name-value pairs and sets the value of the external variable environ to NULL.

"RETURN VALUE"

The clearenv() function returns zero on success, and a non-zero value on failure.

AVAILABILITY

Not in libc4, libc5. In glibc since glibc 2.0.

"CONFORMING TO"

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().

NOTES

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.

"SEE ALSO"

getenv(3), putenv(3), setenv(3), unsetenv(3), environ(5)


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