| .\" Copyright 2001 John Levon <moz@compsoc.man.ac.uk> |
| .\" |
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| .\" Additions, aeb, 2001-10-17. |
| .TH CLEARENV 3 2010-10-04 "Linux" "Linux Programmer's Manual" |
| .SH NAME |
| clearenv \- clear the environment |
| .SH SYNOPSIS |
| .nf |
| .B #include <stdlib.h> |
| .sp |
| .B "int clearenv(void);" |
| .fi |
| .sp |
| .in -4n |
| Feature Test Macro Requirements for glibc (see |
| .BR feature_test_macros (7)): |
| .in |
| .sp |
| .BR clearenv (): |
| _SVID_SOURCE || _BSD_SOURCE |
| .SH DESCRIPTION |
| The |
| .BR clearenv () |
| function clears the environment of all name-value |
| pairs and sets the value of the external variable |
| .I environ |
| to NULL. |
| .SH "RETURN VALUE" |
| The |
| .BR clearenv () |
| function returns zero on success, and a nonzero |
| value on failure. |
| .\" Most versions of UNIX return -1 on error, or do not even have errors. |
| .\" Glibc info and the Watcom C library document "a nonzero value". |
| .SH VERSIONS |
| Not in libc4, libc5. |
| In glibc since glibc 2.0. |
| .SH "CONFORMING TO" |
| Various UNIX variants (DG/UX, HP-UX, QNX, ...). |
| POSIX.9 (bindings for FORTRAN77). |
| POSIX.1-1996 did not accept |
| .BR clearenv () |
| and |
| .BR 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 |
| .BR putenv (3), |
| and rejected |
| .BR clearenv (). |
| .SH NOTES |
| Used in security-conscious applications. |
| If it is unavailable |
| the assignment |
| .nf |
| |
| environ = NULL; |
| |
| .fi |
| will probably do. |
| .LP |
| The DG/UX and Tru64 man pages write: If |
| .I environ |
| has been modified by anything other than the |
| .BR putenv (3), |
| .BR getenv (3), |
| or |
| .BR clearenv () |
| functions, then |
| .BR clearenv () |
| will return an error and the process environment will remain unchanged. |
| .\" .LP |
| .\" HP-UX has a ENOMEM error return. |
| .SH "SEE ALSO" |
| .BR getenv (3), |
| .BR putenv (3), |
| .BR setenv (3), |
| .BR unsetenv (3), |
| .BR environ (7) |
