.\" Copyright 2001 John Levon <moz@compsoc.man.ac.uk>
.\"
+.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
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.\" the source, must acknowledge the copyright and authors of this work.
+.\" %%%LICENSE_END
.\"
.\" Additions, aeb, 2001-10-17.
-.TH CLEARENV 3 2001-10-17 "Linux Programmer's Manual"
+.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
-.BI "int clearenv(void);"
+.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 \fBclearenv\fP() function clears the environment of all name-value
+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 \fBclearenv\fP() function returns zero on success, and a non-zero
+.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 non-zero value".
-.SH AVAILABILITY
+.\" 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, ...).
+.SH CONFORMING TO
+Various UNIX variants (DG/UX, HP-UX, QNX, ...).
POSIX.9 (bindings for FORTRAN77).
-POSIX.1-1996 did not accept \fBclearenv\fP() and \fIputenv\fP(3),
+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 \fIputenv\fP(3), and rejected \fBclearenv\fP().
+only adds
+.BR putenv (3),
+and rejected
+.BR clearenv ().
.SH NOTES
Used in security-conscious applications.
If it is unavailable
the assignment
-.RS
.nf
+
environ = NULL;
+
.fi
-.RE
will probably do.
.LP
-The DG/UX and Tru64 manpages write: If
+The DG/UX and Tru64 man pages write: If
.I environ
has been modified by anything other than the
.BR putenv (3),
will return an error and the process environment will remain unchanged.
.\" .LP
.\" HP-UX has a ENOMEM error return.
-.SH "SEE ALSO"
+.SH SEE ALSO
.BR getenv (3),
.BR putenv (3),
.BR setenv (3),