man/man7/environ.7

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.Dd September 3, 2023
.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 to each process by
.Xr execve 2
when a process begins.
By convention these strings have the form
.Va name Ns No = Ns Ar value ,
and are referred to as
.Dq environment variables .
A process can query, update, and delete these strings using the
.Xr getenv 3 ,
.Xr setenv 3 ,
and
.Xr unsetenv 3
functions, respectively.
The shells also provide commands to manipulate the environment;
they are described in the respective shell manual pages.
.Pp
What follows is a list of environment variables typically
seen on a
.Ux
system.
It includes only those variables that a user can expect to see during their
day-to-day use of the system, and is far from complete.
Environment variables specific to a particular program or library function
are documented in the
.Sx ENVIRONMENT
section of the appropriate manual page.
.Sh ENVIRONMENT
.Bl -tag -width LD_LIBRARY_PATH
.It Ev ARCHLEVEL
On
.Em amd64 ,
controls the level of SIMD enhancements used.
See
.Xr simd 7
for details.
.It Ev BLOCKSIZE
The size of the block units used by several disk-related commands,
most notably
.Xr df 1 ,
.Xr du 1
and
.Xr ls 1 .
.Ev BLOCKSIZE
may be specified in units of a byte by specifying a number,
in units of a kilobyte by specifying a number followed by
.Ql K
or
.Ql k ,
in units of a megabyte by specifying a number followed by
.Ql M
or
.Ql m ,
and in units of a gigabyte by specifying a number followed
by
.Ql G
or
.Ql g .
Sizes less than 512 bytes or greater than a gigabyte are ignored.
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 MANPATH
The sequence of directories, separated by colons, searched by
.Xr man 1
when looking for manual pages.
.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 POSIXLY_CORRECT
When set to any value, this environment variable modifies the behaviour
of certain commands to (mostly) execute in a strictly POSIX-compliant manner.
.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 Pq Pa ports/textproc/groff
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
.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
.Pa /tmp
or
.Pa /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
.Pa /usr/share/zoneinfo .
For example, the command
.Pp
.Dl env TZ=America/Los_Angeles date
.Pp
displays the current time in California.
See
.Xr tzset 3
for more information.
.It Ev USER
The login name of the user.
It is recommended that portable applications use
.Ev LOGNAME
instead.
.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 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 getbsize 3 ,
.Xr getenv 3 ,
.Xr setenv 3 ,
.Xr setlocale 3 ,
.Xr system 3 ,
.Xr termcap 3 ,
.Xr termcap 5 ,
.Xr simd 7
.Sh HISTORY
The
.Nm
manual page appeared in
.At v7 .