CLEARENV - reference manual online

Clear the environment.

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 || _BSD_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 Available since glibc 2.0.
ATTRIBUTES For an explanation of the terms used in this section, see attributes(7). ┌───────────┬───────────────┬─────────────────────┐ │Interface │ Attribute │ Value │ ├───────────┼───────────────┼─────────────────────┤ │clearenv() │ Thread safety │ MT-Unsafe const:env │ └───────────┴───────────────┴─────────────────────┘
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 adds only 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 4.04 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at
Linux 2015-07-23 CLEARENV(3)
This manual Reference Other manuals
clearenv(3) referred by environ(7) | getenv(3) | kdb-elektrify-getenv(1) | md_src_libgetenv_README(3elektra) | putenv(3) | setenv(3)
refer to attributes(7) | environ(7) | feature_test_macros(7) | getenv(3) | putenv(3) | setenv(3)