[apple/libc.git] / man / environ.7

.\"	$NetBSD: environ.7,v 1.4 1995/07/03 19:45:07 jtc Exp $
.\"
.\" Copyright (c) 1983, 1990, 1993
.\"	The Regents of the University of California.  All rights reserved.
.\"
.\" 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.
.\"
.\"	@(#)environ.7	8.3 (Berkeley) 4/19/94
.\"
.Dd April 19, 1994
.Dt ENVIRON 7
.Os BSD 4.2
.Sh NAME
.Nm environ
.Nd user environment
.Sh SYNOPSIS
.Ar extern char **environ ;
.Sh DESCRIPTION
An array of strings called the
.Ar environment
is made available by
.Xr execve  2
when a process begins.  By convention these strings have the form
.Dq Ar name=value .
The following names are used by various commands:
.Bl -tag -width BLOCKSIZE
.It Ev BLOCKSIZE
The size of the block units used by several commands, most notably
.Xr df 1 ,
.Xr du 1
and
.Xr ls 1 .
BLOCKSIZE may be specified in units of a byte by specifying a number, 
in units of a kilobyte by specifying a number followed by ``K'' or
``k'', in units of a megabyte by specifying a number followed by ``M''
or ``m'' and in units of a gigabyte by specifying a number followed
by ``G'' or ``g''.
Sizes less than 512 bytes or greater than a gigabyte are ignored.
.It Ev EXINIT
A startup list of commands read by
.Xr ex  1
and
.Xr vi  1  .
.It Ev HOME
A user's login directory, set by
.Xr login  1
from the password file
.Xr passwd  5  .
.It Ev PATH
The sequence of directories, separated by colons, searched by
.Xr csh  1  ,
.Xr sh  1 ,
.Xr system  3  ,
.Xr execvp  3 ,
etc, when looking for an executable file.
PATH is set to ``/usr/bin:/bin'' initially by
.Xr login  1  .
.It Ev PRINTER
The name of the default printer to be used by
.Xr lpr  1  ,
.Xr lpq  1 ,
and
.Xr lprm  1  .
.It Ev SHELL
The full pathname of the user's login shell.
.It Ev TERM
The kind of terminal for which output is to be prepared.
This information is used by commands, such as
.Xr nroff  1
which may exploit special terminal capabilities.  See
.Xr termcap 3
and
.Xr terminfo 5 .
.It Ev TMPDIR
The directory in which to store temporary files.
Most applications use either
.Dq /tmp
or
.Dq /var/tmp .
Setting this variable will make them use another directory.
.It Ev TZ
The timezone to use when displaying dates.
The normal format is a pathname relative to
.Dq /usr/share/zoneinfo .
For example, the command
.Dq env TZ=US/Pacific date
displays the current time in California.
See
.Xr tzset 3
for more information.
.It Ev LOGNAME
The login name of the user.
.It Ev USER
Deprecated synonym of
.Ev LOGNAME
(for backwards compatibility).
.El
.Pp
Further names may be placed in the environment by the
.Xr export
command and
.Ar name=value
arguments in
.Xr sh  1  ,
or by the
.Xr setenv
command if you use
.Xr csh  1  .
It is unwise to change certain
.Xr sh  1
variables that are frequently exported by
.Pa .profile
files, such as
.Ev MAIL ,
.Ev PS1 ,
.Ev PS2 ,
and
.Ev IFS ,
unless you know what you are doing.
.Sh PROGRAMMING
Programs can query and modify the environment, using the environment routines
.Xr getenv 3 ,
.Xr putenv 3 ,
.Xr setenv 3
and
.Xr unsetenv 3 .
Direct access can be made through the global variable
.Va environ ,
though it is recommended that changes to the enviroment still be made through
the environment routines.
.Pp
Shared libraries and bundles don't have direct access to
.Va environ ,
which is only available to the loader
.Xr ld 1
when a complete program is being linked.
The environment routines can still be used, but if direct access to
.Va environ
is needed, the
.Fn _NSGetEnviron
routine, defined in
.In crt_externs.h ,
can be used to retrieve the address of
.Va environ
at runtime.
.Sh SEE ALSO
.Xr csh 1 ,
.Xr ex 1 ,
.Xr login 1 ,
.Xr sh 1 ,
.Xr getenv 3 ,
.Xr putenv 3 ,
.Xr setenv 3 ,
.Xr unsetenv 3 ,
.Xr execve 2 ,
.Xr execle 3 ,
.Xr system 3 ,
.Xr termcap 3 ,
.Xr terminfo 5
.Sh HISTORY
The
.Nm environ
manual page appeared in
.Bx 4.2 .
Commit	Line	Data
224c7076 A	1	.\" $NetBSD: environ.7,v 1.4 1995/07/03 19:45:07 jtc Exp $
	2	.\"
	3	.\" Copyright (c) 1983, 1990, 1993
	4	.\" The Regents of the University of California. All rights reserved.
	5	.\"
	6	.\" Redistribution and use in source and binary forms, with or without
	7	.\" modification, are permitted provided that the following conditions
	8	.\" are met:
	9	.\" 1. Redistributions of source code must retain the above copyright
	10	.\" notice, this list of conditions and the following disclaimer.
	11	.\" 2. Redistributions in binary form must reproduce the above copyright
	12	.\" notice, this list of conditions and the following disclaimer in the
	13	.\" documentation and/or other materials provided with the distribution.
	14	.\" 3. All advertising materials mentioning features or use of this software
	15	.\" must display the following acknowledgement:
	16	.\" This product includes software developed by the University of
	17	.\" California, Berkeley and its contributors.
	18	.\" 4. Neither the name of the University nor the names of its contributors
	19	.\" may be used to endorse or promote products derived from this software
	20	.\" without specific prior written permission.
	21	.\"
	22	.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	23	.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	24	.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	25	.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	26	.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	27	.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	28	.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	29	.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	30	.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	31	.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	32	.\" SUCH DAMAGE.
	33	.\"
	34	.\" @(#)environ.7 8.3 (Berkeley) 4/19/94
	35	.\"
	36	.Dd April 19, 1994
	37	.Dt ENVIRON 7
	38	.Os BSD 4.2
	39	.Sh NAME
	40	.Nm environ
	41	.Nd user environment
	42	.Sh SYNOPSIS
	43	.Ar extern char **environ ;
	44	.Sh DESCRIPTION
	45	An array of strings called the
	46	.Ar environment
	47	is made available by
	48	.Xr execve 2
	49	when a process begins. By convention these strings have the form
	50	.Dq Ar name=value .
	51	The following names are used by various commands:
	52	.Bl -tag -width BLOCKSIZE
	53	.It Ev BLOCKSIZE
	54	The size of the block units used by several commands, most notably
	55	.Xr df 1 ,
	56	.Xr du 1
	57	and
	58	.Xr ls 1 .
	59	BLOCKSIZE may be specified in units of a byte by specifying a number,
	60	in units of a kilobyte by specifying a number followed by ``K'' or
	61	``k'', in units of a megabyte by specifying a number followed by ``M''
	62	or ``m'' and in units of a gigabyte by specifying a number followed
	63	by ``G'' or ``g''.
	64	Sizes less than 512 bytes or greater than a gigabyte are ignored.
65	.It Ev EXINIT
66	A startup list of commands read by
6465356a	67	.Xr ex 1
224c7076 A	68	and
	69	.Xr vi 1 .
	70	.It Ev HOME
	71	A user's login directory, set by
	72	.Xr login 1
	73	from the password file
	74	.Xr passwd 5 .
	75	.It Ev PATH
	76	The sequence of directories, separated by colons, searched by
	77	.Xr csh 1 ,
	78	.Xr sh 1 ,
	79	.Xr system 3 ,
	80	.Xr execvp 3 ,
	81	etc, when looking for an executable file.
	82	PATH is set to ``/usr/bin:/bin'' initially by
	83	.Xr login 1 .
	84	.It Ev PRINTER
	85	The name of the default printer to be used by
	86	.Xr lpr 1 ,
	87	.Xr lpq 1 ,
	88	and
	89	.Xr lprm 1 .
	90	.It Ev SHELL
	91	The full pathname of the user's login shell.
	92	.It Ev TERM
	93	The kind of terminal for which output is to be prepared.
	94	This information is used by commands, such as
	95	.Xr nroff 1
224c7076	96	which may exploit special terminal capabilities. See
6465356a	97	.Xr termcap 3
224c7076	98	and
6465356a	99	.Xr terminfo 5 .
224c7076 A	100	.It Ev TMPDIR
	101	The directory in which to store temporary files.
	102	Most applications use either
	103	.Dq /tmp
	104	or
	105	.Dq /var/tmp .
	106	Setting this variable will make them use another directory.
	107	.It Ev TZ
	108	The timezone to use when displaying dates.
	109	The normal format is a pathname relative to
	110	.Dq /usr/share/zoneinfo .
	111	For example, the command
	112	.Dq env TZ=US/Pacific date
	113	displays the current time in California.
	114	See
	115	.Xr tzset 3
	116	for more information.
	117	.It Ev LOGNAME
	118	The login name of the user.
	119	.It Ev USER
	120	Deprecated synonym of
	121	.Ev LOGNAME
	122	(for backwards compatibility).
	123	.El
	124	.Pp
	125	Further names may be placed in the environment by the
	126	.Xr export
	127	command and
	128	.Ar name=value
	129	arguments in
	130	.Xr sh 1 ,
	131	or by the
	132	.Xr setenv
	133	command if you use
	134	.Xr csh 1 .
	135	It is unwise to change certain
	136	.Xr sh 1
	137	variables that are frequently exported by
	138	.Pa .profile
	139	files, such as
	140	.Ev MAIL ,
	141	.Ev PS1 ,
	142	.Ev PS2 ,
	143	and
	144	.Ev IFS ,
	145	unless you know what you are doing.
	146	.Sh PROGRAMMING
	147	Programs can query and modify the environment, using the environment routines
	148	.Xr getenv 3 ,
	149	.Xr putenv 3 ,
	150	.Xr setenv 3
	151	and
	152	.Xr unsetenv 3 .
	153	Direct access can be made through the global variable
	154	.Va environ ,
	155	though it is recommended that changes to the enviroment still be made through
	156	the environment routines.
	157	.Pp
	158	Shared libraries and bundles don't have direct access to
	159	.Va environ ,
	160	which is only available to the loader
	161	.Xr ld 1
	162	when a complete program is being linked.
	163	The environment routines can still be used, but if direct access to
164	.Va environ
165	is needed, the
166	.Fn _NSGetEnviron
167	routine, defined in
168	.In crt_externs.h ,
169	can be used to retrieve the address of
170	.Va environ
171	at runtime.
172	.Sh SEE ALSO
173	.Xr csh 1 ,
174	.Xr ex 1 ,
175	.Xr login 1 ,
176	.Xr sh 1 ,
177	.Xr getenv 3 ,
178	.Xr putenv 3 ,
179	.Xr setenv 3 ,
180	.Xr unsetenv 3 ,
181	.Xr execve 2 ,
182	.Xr execle 3 ,
183	.Xr system 3 ,
184	.Xr termcap 3 ,
6465356a	185	.Xr terminfo 5
224c7076 A	186	.Sh HISTORY
	187	The
	188	.Nm environ
	189	manual page appeared in
	190	.Bx 4.2 .