V7/usr/man/man5/environ.5

.TH ENVIRON 5
.SH NAME
environ \- user environment
.SH SYNOPSIS
.B extern char **environ;
.SH DESCRIPTION
An array of strings called the `environment' is
made available by
.IR exec (2)
when a process begins.
By convention these strings have the form
`name=value'.
The following names are used by various commands:
.TP
PATH
The sequence of directory prefixes that
.I sh, time,
.IR nice (1),
etc.,
apply in searching for a file known by an incomplete path name.
The prefixes are separated by `:'.
.IR Login (1)
sets PATH=:/bin:/usr/bin.
.TP
HOME
A user's login directory, set by
.IR login (1)
from the password file
.IR passwd (5).
.TP
TERM
The kind of terminal for which output is to be prepared.
This information is used by commands, such as
.I nroff
or
.IR plot (1),
which may exploit special terminal capabilities.
See
.IR term (7)
for a list of terminal types.
.PP
Further names may be placed in the environment by
the
.I export
command and `name=value' arguments in
.IR sh (1),
or by 
.IR exec (2).
It is unwise to conflict with
certain Shell variables that are frequently exported by
`.profile' files:
MAIL, PS1, PS2, IFS.
.SH SEE ALSO
exec(2), sh(1), term(7), login(1)