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

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.\"	@(#)environ.7	8.3 (Berkeley) 4/19/94
.\" $FreeBSD$
.\"
.Dd April 12, 2003
.Dt ENVIRON 7
.Os
.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 LC_MONETARY
.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 .
This variable is processed by the
.Xr getbsize 3
function.
.It Ev COLUMNS
The user's preferred width in column positions for the terminal.
Utilities such as
.Xr ls 1
and
.Xr who 1
use this to format output into columns.
If unset or empty, utilities will use an
.Xr ioctl 2
call to ask the terminal driver for the width.
.It Ev EDITOR
Default editor name.
.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 LANG
This variable configures all programs which use
.Xr setlocale 3
to use the specified locale unless the
.Ev LC_*
variables are set.
.It Ev LC_ALL
Overrides the values of
.Ev LC_COLLATE ,
.Ev LC_CTYPE ,
.Ev LC_MESSAGES ,
.Ev LC_MONETARY ,
.Ev LC_NUMERIC ,
.Ev LC_TIME
and
.Ev LANG .
.It Ev LC_COLLATE
Locale to be used for ordering of strings.
.It Ev LC_CTYPE
Locale to be used for character classification
(letter, space, digit, etc.) and for interpreting byte sequences as
multibyte characters.
.It Ev LC_MESSAGES
Locale to be used for diagnostic messages.
.It Ev LC_MONETARY
Locale to be used for interpreting monetary input
and formatting output.
.It Ev LC_NUMERIC
Locale to be used for interpreting numeric input and
formatting output.
.It Ev LC_TIME
Locale to be used for interpreting dates input and
for formatting output.
.It Ev MAIL
The location of the user's
mailbox instead of the default in /var/mail,
used by
.Xr mail 1 ,
.Xr sh 1 ,
and many other mail clients.
.It Ev NLSPATH
List of directories to be searched for the message catalog referred to by
.Ev LC_MESSAGES .
See
.Xr catopen 3 .
.It Ev PAGER
Default paginator program.
The program specified by this variable is used by
.Xr mail 1 ,
.Xr man 1 ,
.Xr ftp 1 ,
etc, to display information which is longer than the current display.
.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.
.Ev 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 PWD
The current directory pathname.
.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
or
.Xr plot 1
which may exploit special terminal capabilities.
See
.Pa /usr/share/misc/termcap
.Pq Xr termcap 5
for a list of terminal types.
.It Ev TERMCAP
The string describing the terminal in
.Ev TERM ,
or, if
it begins with a '/', the name of the termcap file.
See
.Ev TERMPATH
below, and
.Xr termcap 5 .
.It Ev TERMPATH
A sequence of pathnames of termcap files, separated by colons or spaces,
which are searched for terminal descriptions in the order listed.
Having
no
.Ev TERMPATH
is equivalent to a
.Ev TERMPATH
of
.Dq Pa $HOME/.termcap:/etc/termcap .
.Ev TERMPATH
is ignored if
.Ev TERMCAP
contains a full pathname.
.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 Pa /usr/share/zoneinfo .
For example, the command
.Dq env TZ=America/Los_Angeles date
displays the current time in California.
See
.Xr tzset 3
for more information.
.It Ev USER
The login name of the user.
.El
.Pp
Further names may be placed in the environment by the
.Ic export
command and
.Ar name=value
arguments in
.Xr sh 1 ,
or by the
.Ic 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.
.Pp
The current environment variables can be printed with
.Xr env 1 ,
.Xr set 1
or
.Xr printenv 1
in
.Xr sh 1
and
.Xr env 1 ,
.Xr printenv 1
or the
.Cm printenv
built-in command in
.Xr csh 1 .
.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 cd 1 ,
.Xr csh 1 ,
.Xr env 1 ,
.Xr ex 1 ,
.Xr login 1 ,
.Xr printenv 1 ,
.Xr sh 1 ,
.Xr execve 2 ,
.Xr execle 3 ,
.Xr getenv 3 ,
.Xr putenv 3 ,
.Xr setenv 3 ,
.Xr unsetenv 3 ,
.Xr setlocale 3 ,
.Xr system 3 ,
.Xr termcap 3 ,
.Xr termcap 5
.Sh HISTORY
The
.Nm
manual page appeared in
.Bx 4.2 .