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.TH UNSETENV 3C "Dec 20, 2014"
.SH NAME
unsetenv \- remove an environment variable
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>

\fBint\fR \fBunsetenv\fR(\fBconst char *\fR\fIname\fR);
.fi

.SH DESCRIPTION
.LP
The \fBunsetenv()\fR function removes an environment variable from the
environment of the calling process. The \fIname\fR argument points to a string
that is the name of the variable to be removed. The named argument cannot
contain an '=' character. If the named variable does not exist in the current
environment, the environment is unchanged and the function is considered to
have completed successfully.
.sp
.LP
If the application modifies \fIenviron\fR or the pointers to which it points,
the behavior of \fBunsetenv()\fR is undefined. The \fBunsetenv()\fR function
updates the list of pointers to which \fIenviron\fR points.
.SH RETURN VALUES
.LP
Upon successful completion, 0 is returned. Otherwise, -1 is returned,
\fBerrno\fR set to indicate the error, and the environment is left unchanged.
.SH ERRORS
.LP
The \fBunsetenv()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The \fIname\fR argument is a null pointer, points to an empty string, or points
to a string containing an '=' character.
.RE

.SH ATTRIBUTES
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.LP
.BR clearenv (3C),
.BR getenv (3C),
.BR setenv (3C),
.BR attributes (7),
.BR standards (7)