mirror of
https://git.FreeBSD.org/src.git
synced 2024-12-13 10:02:38 +00:00
175 lines
4.4 KiB
Groff
175 lines
4.4 KiB
Groff
.\" Copyright (c) 1988, 1991, 1993
|
|
.\" The Regents of the University of California. All rights reserved.
|
|
.\"
|
|
.\" This code is derived from software contributed to Berkeley by
|
|
.\" the American National Standards Committee X3, on Information
|
|
.\" Processing Systems.
|
|
.\"
|
|
.\" Redistribution and use in source and binary forms, with or without
|
|
.\" modification, are permitted provided that the following conditions
|
|
.\" are met:
|
|
.\" 1. Redistributions of source code must retain the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer.
|
|
.\" 2. Redistributions in binary form must reproduce the above copyright
|
|
.\" notice, this list of conditions and the following disclaimer in the
|
|
.\" documentation and/or other materials provided with the distribution.
|
|
.\" 3. All advertising materials mentioning features or use of this software
|
|
.\" must display the following acknowledgement:
|
|
.\" This product includes software developed by the University of
|
|
.\" California, Berkeley and its contributors.
|
|
.\" 4. Neither the name of the University nor the names of its contributors
|
|
.\" may be used to endorse or promote products derived from this software
|
|
.\" without specific prior written permission.
|
|
.\"
|
|
.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
|
|
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
|
|
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
|
|
.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
|
|
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
|
|
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
|
|
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
|
|
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
|
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
|
|
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
|
|
.\" SUCH DAMAGE.
|
|
.\"
|
|
.\" @(#)getenv.3 8.2 (Berkeley) 12/11/93
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd December 11, 1993
|
|
.Dt GETENV 3
|
|
.Os
|
|
.Sh NAME
|
|
.Nm getenv ,
|
|
.Nm putenv ,
|
|
.Nm setenv ,
|
|
.Nm unsetenv
|
|
.Nd environment variable functions
|
|
.Sh LIBRARY
|
|
.Lb libc
|
|
.Sh SYNOPSIS
|
|
.In stdlib.h
|
|
.Ft char *
|
|
.Fn getenv "const char *name"
|
|
.Ft int
|
|
.Fn setenv "const char *name" "const char *value" "int overwrite"
|
|
.Ft int
|
|
.Fn putenv "const char *string"
|
|
.Ft void
|
|
.Fn unsetenv "const char *name"
|
|
.Sh DESCRIPTION
|
|
These functions set, unset and fetch environment variables from the
|
|
host
|
|
.Em environment list .
|
|
For compatibility with differing environment conventions,
|
|
the given arguments
|
|
.Fa name
|
|
and
|
|
.Fa value
|
|
may be appended and prepended,
|
|
respectively,
|
|
with an equal sign
|
|
.Dq Li \&= .
|
|
.Pp
|
|
The
|
|
.Fn getenv
|
|
function obtains the current value of the environment variable,
|
|
.Fa name .
|
|
.Pp
|
|
The
|
|
.Fn setenv
|
|
function inserts or resets the environment variable
|
|
.Fa name
|
|
in the current environment list.
|
|
If the variable
|
|
.Fa name
|
|
does not exist in the list,
|
|
it is inserted with the given
|
|
.Fa value .
|
|
If the variable does exist, the argument
|
|
.Fa overwrite
|
|
is tested; if
|
|
.Fa overwrite
|
|
is
|
|
zero, the
|
|
variable is not reset, otherwise it is reset
|
|
to the given
|
|
.Fa value .
|
|
.Pp
|
|
The
|
|
.Fn putenv
|
|
function takes an argument of the form ``name=value'' and is
|
|
equivalent to:
|
|
.Bd -literal -offset indent
|
|
setenv(name, value, 1);
|
|
.Ed
|
|
.Pp
|
|
The
|
|
.Fn unsetenv
|
|
function
|
|
deletes all instances of the variable name pointed to by
|
|
.Fa name
|
|
from the list.
|
|
.Sh RETURN VALUES
|
|
The
|
|
.Fn getenv
|
|
function returns the value of the environment variable as a
|
|
.Dv NUL Ns
|
|
-terminated string.
|
|
If the variable
|
|
.Fa name
|
|
is not in the current environment,
|
|
.Dv NULL
|
|
is returned.
|
|
.Pp
|
|
.Rv -std setenv putenv
|
|
.Sh ERRORS
|
|
.Bl -tag -width Er
|
|
.It Bq Er ENOMEM
|
|
The function
|
|
.Fn setenv
|
|
or
|
|
.Fn putenv
|
|
failed because they were unable to allocate memory for the environment.
|
|
.El
|
|
.Sh SEE ALSO
|
|
.Xr csh 1 ,
|
|
.Xr sh 1 ,
|
|
.Xr execve 2 ,
|
|
.Xr environ 7
|
|
.Sh STANDARDS
|
|
The
|
|
.Fn getenv
|
|
function conforms to
|
|
.St -isoC .
|
|
.Sh HISTORY
|
|
The functions
|
|
.Fn setenv
|
|
and
|
|
.Fn unsetenv
|
|
appeared in
|
|
.At v7 .
|
|
The
|
|
.Fn putenv
|
|
function appeared in
|
|
.Bx 4.3 Reno .
|
|
.Sh BUGS
|
|
Successive calls to
|
|
.Fn setenv
|
|
or
|
|
.Fn putenv
|
|
assigning a differently sized
|
|
.Fa value
|
|
to the same
|
|
.Fa name
|
|
will result in a memory leak.
|
|
The
|
|
.Fx
|
|
semantics for these functions
|
|
(namely, that the contents of
|
|
.Fa value
|
|
are copied and that old values remain accessible indefinitely) make this
|
|
bug unavoidable.
|
|
Future versions may eliminate one or both of these
|
|
semantic guarantees in order to fix the bug.
|