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.TH SETENV 3C "Mar 31, 2002"
.SH NAME
setenv \- add or change environment variable
.SH SYNOPSIS
.LP
.nf
#include <stdlib.h>

\fBint\fR \fBsetenv\fR(\fBconst char *\fR\fIenvname\fR, \fBconst char *\fR\fIenvval\fR,
     \fBint\fR \fIoverwrite\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBsetenv()\fR function updates or adds a variable in the environment of
the calling process.  The \fIenvname\fR argument points to a string containing
the name of an environment variable to be added or altered. The environment
variable is set to the value to which \fIenvval\fR points. The function fails
if \fIenvname\fR points to a string which contains an '=' character. If the
environment variable named by \fIenvname\fR already exists and the value of
\fIoverwrite\fR is non-zero, the function returns successfully and the
environment is updated. If the environment variable named by \fIenvname\fR
already exists and the value of \fIoverwrite\fR is zero, the function returns
successfully and the environment remains unchanged.
.sp
.LP
If the application modifies \fIenviron\fR or the pointers to which it points,
the behavior of \fBsetenv()\fR is undefined. The \fBsetenv()\fR function
updates the list of pointers to which \fIenviron\fR points.
.sp
.LP
The strings described by \fIenvname\fR and \fIenvval\fR are copied by this
function.
.SH RETURN VALUES
.sp
.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
.sp
.LP
The \fBsetenv()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
The \fIenvname\fR argument is a null pointer, points to an empty string, or
points to a string containing an '=' character.
.RE

.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 10n
Insufficient memory was available to add a variable or its value to the
environment.
.RE

.SH ATTRIBUTES
.sp
.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
.sp
.LP
.BR getenv (3C),
.BR unsetenv (3C),
.BR attributes (7),
.BR standards (7)