1 .\" Copyright (c) 1993 Michael Haardt (michael@moria.de),
2 .\" Fri Apr 2 11:32:09 MET DST 1993
3 .\" and Andries Brouwer (aeb@cwi.nl), Fri Feb 14 21:47:50 1997.
5 .\" %%%LICENSE_START(GPLv2+_DOC_FULL)
6 .\" This is free documentation; you can redistribute it and/or
7 .\" modify it under the terms of the GNU General Public License as
8 .\" published by the Free Software Foundation; either version 2 of
9 .\" the License, or (at your option) any later version.
11 .\" The GNU General Public License's references to "object code"
12 .\" and "executables" are to be interpreted as the output of any
13 .\" document formatting or typesetting system, including
14 .\" intermediate and printed output.
16 .\" This manual is distributed in the hope that it will be useful,
17 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of
18 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 .\" GNU General Public License for more details.
21 .\" You should have received a copy of the GNU General Public
22 .\" License along with this manual; if not, see
23 .\" <http://www.gnu.org/licenses/>.
26 .\" Modified Sun Jul 25 10:45:30 1993 by Rik Faith (faith@cs.unc.edu)
27 .\" Modified Sun Jul 21 21:25:26 1996 by Andries Brouwer (aeb@cwi.nl)
28 .\" Modified Mon Oct 21 17:47:19 1996 by Eric S. Raymond (esr@thyrsus.com)
29 .\" Modified Wed Aug 27 20:28:58 1997 by Nicolás Lichtmaier (nick@debian.org)
30 .\" Modified Mon Sep 21 00:00:26 1998 by Andries Brouwer (aeb@cwi.nl)
31 .\" Modified Wed Jan 24 06:37:24 2001 by Eric S. Raymond (esr@thyrsus.com)
32 .\" Modified Thu Dec 13 23:53:27 2001 by Martin Schulze <joey@infodrom.org>
34 .TH ENVIRON 7 2014-01-18 "Linux" "Linux Programmer's Manual"
36 environ \- user environment
39 .BI "extern char **" environ ;
45 points to an array of pointers to strings called the "environment".
46 The last pointer in this array has the value NULL.
47 (This variable must be declared in the user program,
48 but is declared in the header file
50 in case the header files came from libc4 or libc5, and
51 in case they came from glibc and
54 This array of strings is made available to the process by the
56 call that started the process.
58 By convention the strings in
60 have the form "\fIname\fP\fB=\fP\fIvalue\fP".
64 The name of the logged-in user (used by some BSD-derived programs).
67 The name of the logged-in user (used by some System-V derived programs).
70 A user's login directory, set by
72 from the password file
76 The name of a locale to use for locale categories when not overridden
79 or more specific environment variables such as
89 for further details of the
91 environment variables).
94 The sequence of directory prefixes that
97 programs apply in searching for a file known by an incomplete pathname.
98 The prefixes are separated by \(aq\fB:\fP\(aq.
101 used by some shells to find the target
102 of a change directory command,
106 to find manual pages, and so on)
109 The current working directory.
113 The pathname of the user's login shell.
116 The terminal type for which output is to be prepared.
119 The user's preferred utility to display text files.
122 The user's preferred utility to edit text files.
125 .\" The user's preferred utility to browse URLs. Sequence of colon-separated
126 .\" browser commands. See http://www.catb.org/~esr/BROWSER/ .
128 Further names may be placed in the environment by the
130 command and "name=value" in
136 Arguments may also be placed in the
137 environment at the point of an
139 A C program can manipulate its environment using the functions
146 Note that the behavior of many programs and library routines is
147 influenced by the presence or value of certain environment variables.
151 .BR LANG ", " LANGUAGE ", " NLSPATH ", " LOCPATH ", "
152 .BR LC_ALL ", " LC_MESSAGES ", "
153 and so on influence locale handling; see
160 influences the path prefix of names created by
162 and other routines, and the temporary directory used by
166 .BR LD_LIBRARY_PATH ", " LD_PRELOAD
167 and other LD_* variables influence
168 the behavior of the dynamic loader/linker.
171 makes certain programs and library routines follow
172 the prescriptions of POSIX.
182 gives the name of a file containing aliases
184 .BR gethostbyname (3).
187 give timezone information used by
189 and through that by functions like
198 gives information on how to address a given terminal
199 (or gives the name of a file containing such information).
201 .BR COLUMNS " and " LINES
202 tell applications about the window size, possibly overriding the actual size.
204 .BR PRINTER " or " LPDEST
205 may specify the desired printer to use.
211 Clearly there is a security risk here.
212 Many a system command has been
213 tricked into mischief by a user who specified unusual values for
214 .BR IFS " or " LD_LIBRARY_PATH .
216 There is also the risk of name space pollution.
221 allow overriding of default utility names from the
222 environment with similarly named variables in all caps.
225 to select the desired C compiler (and similarly
235 However, in some traditional uses such an environment variable
236 gives options for the program instead of a pathname.
242 Such usage is considered mistaken, and to be avoided in new
246 should consider renaming their option to
263 This page is part of release 3.68 of the Linux
266 A description of the project,
267 information about reporting bugs,
268 and the latest version of this page,
270 \%http://www.kernel.org/doc/man\-pages/.