clearenv(3) Library Functions Manual clearenv(3)NAME
clearenv - Clears the process environment
LIBRARY
Standard C Library (libc.a)
SYNOPSIS
#include <stdlib.h>
int clearenv ( void );
DESCRIPTION
The clearenv() function clears the process environment. No environment variables are defined immediately after a call to clearenv(). The
clearenv() function sets the value of the external variable environ to NULL.
NOTES
Trial use
RETURN VALUES
Upon successful completion, the clearenv() function returns 0 (zero). Otherwise, it returns -1.
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.
RELATED INFORMATION
Functions: exec(2), getenv(3), putenv(3) delim off
clearenv(3)
Check Out this Related Man Page
CLEARENV(3) Linux Programmer's Manual CLEARENV(3)NAME
clearenv - clear the environment
SYNOPSIS
#include <stdlib.h>
int clearenv(void);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
clearenv(): _SVID_SOURCE || _XOPEN_SOURCE
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 nonzero value on failure.
VERSIONS
Not in libc4, libc5. In glibc since glibc 2.0.
CONFORMING TO
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 only adds
putenv(3), and rejected clearenv().
NOTES
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.
SEE ALSO getenv(3), putenv(3), setenv(3), unsetenv(3), environ(7)COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2007-07-26 CLEARENV(3)
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