.\"	@(#)getenv.3	6.3 (Berkeley) 03/11/87
.\"
.TH GETENV 3 ""
.AT 3
.SH NAME
getenv, setenv, unsetenv \- manipulate environmental variables
.SH SYNOPSIS
.nf
.B char *getenv(name)
.B char *name;
.PP
.B setenv(name, value, overwrite)
.B char *name, value;
.B int overwrite;
.PP
.B void unsetenv(name)
.B char *name;
.fi
.SH DESCRIPTION
\fIGetenv\fP searches the environment list (see \fIenviron\fP(7))
for a string of the form \fIname\fP\fB=\fP\fIvalue\fP and returns
a pointer to the string \fIvalue\fP if such a string is present,
and 0 (NULL) if it is not.
.PP
\fISetenv\fP searches the environment list as \fIgetenv\fP does; if
the string \fIname\fP is not found, a string of the form
\fIname\fP\fB=\fP\fIvalue\fP is added to the environment.  If it is
found and \fIoverwrite\fP is non-zero, its value is changed to
\fIvalue\fP.  \fISetenv\fP returns 0 on success and -1 on failure.
.PP
\fIUnsetenv\fP removes all occurrences of the string \fIname\fP from
the environment.
.PP
All of these routines permit, but do not require, a trailing equals
(``='') sign on \fIname\fP or a leading equals sign on \fIvalue\fP.
.SH SEE ALSO
csh(1), sh(1), execve(2), environ(7)