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.\"	@(#)environ.7	8.3 (Berkeley) 4/19/94
.\"
.Dd $Mdocdate: October 28 2010 $
.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
.Dq environment
is made available by
.Xr execve 2
when a process begins.
By convention these strings have the form
.Ar name Ns = Ns Ar value .
The following variables are recognized 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 .
May be specified in units of a byte by specifying a number,
in units of a kilobyte by specifying a number followed by
.Sq K
or
.Sq k ,
in units of a megabyte by specifying a number followed by
.Sq M
or
.Sq m ,
or in units of a gigabyte by specifying a number followed
by
.Sq G
or
.Sq g .
Sizes less than 512 bytes or greater than a gigabyte are ignored.
.It Ev EXINIT
A list of startup commands read by
.Xr ex 1
and
.Xr vi 1 .
.It Ev HOME
The user's login directory, set by
.Xr login 1
from the password file
.Xr passwd 5 .
.It Ev LOGNAME
The login name of the user.
.It Ev PATH
The sequence of directories, separated by colons, searched by
.Xr csh 1 ,
.Xr sh 1 ,
.Xr ksh 1 ,
.Xr system 3 ,
.Xr execvp 3 ,
etc. when looking for an executable file.
Initially set to the value of
.Dv _PATH_DEFPATH
by
.Xr login 1 ,
traditionally
.Pa /usr/bin:/bin ,
but expanded to include
.Pa /usr/sbin ,
.Pa /sbin ,
.Pa /usr/X11R6/bin ,
and
.Pa /usr/local/bin
in
.Ox .
.It Ev PRINTER
The name of the default printer to be used by
.Xr lpq 1 ,
.Xr lpr 1 ,
and
.Xr lprm 1 .
.It Ev PWD
The current working directory.
.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 mandoc 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
.Ql / ,
the name of the termcap file.
See
.Ev TERMPATH
below,
.Xr termcap 5 ,
and
.Xr termcap 3 .
.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 time zone to use when displaying dates.
The normal format is a pathname relative to
.Pa /usr/share/zoneinfo .
For example, the command
.Ic env TZ=US/Pacific date
displays the current time in California.
See
.Xr tzset 3
for more information.
.It Ev USER
Deprecated synonym of
.Ev LOGNAME
(for backwards compatibility).
.El
.Pp
Further names may be placed in the environment by the
.Ic export
command and
.Ar name Ns = Ns Ar 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
or
.Xr printenv 1 .
.Sh SEE ALSO
.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 system 3 ,
.Xr termcap 3 ,
.Xr tzset 3 ,
.Xr termcap 5
.Sh HISTORY
The
.Nm
manual page appeared in
.Bx 4.2 .