environ.7

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)environ.7	8.1	9/11/90
.TH environ 7
.SH Name
environ \- user environment
.SH Syntax
.B extern char **environ;
.SH Description
.NXR "environ global variable"
An array of strings, called the environment, is made available by
.PN execve 
when a process begins.  By convention, these strings have the form
.RI `` name = value ''.
.NXR "environment" "strings"
The following names are used by various commands:
.NXR "PATH string"
.TP "\w'TERMCAP 'u"
PATH
The sequence of directory prefixes that
.PN sh , 
.PN time , 
and 
.PN nice 
apply in searching for a file known by an incomplete path name.
The prefixes are separated by a colon (:).
The 
.MS login 1 
command sets 
.PN PATH=:/usr/ucb:/bin:/usr/bin .
.NXR "HOME string"
.TP
HOME
A user's login directory, set by
.PN login
from the password file 
.PN passwd .
.NXR "TERM string"
.TP
TERM
The kind of terminal for which output is to be prepared.
This information is used by commands, such as 
.PN nroff 
or 
.PN plot ,
which may exploit special terminal capabilities.  See 
.PN /etc/termcap
in 
.MS termcap 5 
for a list of terminal types.
.NXR "SHELL string"
.TP
SHELL
The file name of the user's login shell.
.NXR "TERMCAP string"
.TP
TERMCAP
The string describing the terminal in TERM
or the name of the termcap file.  For further information, see
.MS termcap 5 
and
.MS termcap 3x .
.NXR "EXINIT string"
.TP
EXINIT
A startup list of commands read by 
.PN ex , 
.PN edit , 
and 
.PN vi .
.NXR "USER string"
.TP
USER
The login name of the user.
.NXR "PRINTER string"
.TP
PRINTER
The name of the default printer to be used by 
.PN lpr , 
.PN lpq ,
and 
.PN lprm .
.PP
Further names may be placed in the environment by the
.PN export
command and ``name=value'' arguments in 
.PN sh , 
or by the
.PN setenv
command if you use 
.PN csh .
Arguments can also be placed in the environment at the point of an
.PN execve .
It is unwise to conflict with certain 
.PN sh 
variables that are frequently exported by 
.PN .profile 
files:
.PN MAIL ,
.PN PS1 ,
.PN PS2 ,
and
.PN IFS .
.SH See Also
csh(1), ex(1), login(1), sh(1), execve(2), system(3), termcap(3x),
passwd(5), termcap(5)