NAME
environ - user environment
SYNOPSIS
extern char *const *environ;
DESCRIPTION
An array of strings called the `environment' is made avail-
able by execve(2) when a process begins. By convention
these strings have the form `name=value'. The following
names are used by various commands:
PATH The sequence of directory prefixes that sh, time,
nice(1), etc., apply in searching for a file known
by an incomplete path name. The prefixes are
separated by `:'. Login shells set
PATH=:/bin:/usr/bin. Note that the empty space
between the `=' and the `:' indicates the current
directory. Security aware people move the extra `:'
to the end of their path or omit it.
HOME A user's login directory, set by login(1) from the
password file passwd(5).
TERM The kind of terminal for which output is to be
prepared. This information is used by programs that
wish to exploit special terminal capabilities, a
screen oriented text editor for instance. The ter-
minal type is set by login(1) from the tty database
ttytab(5).
SHELL The file name of the users login shell, set by
login(1) from the password file passwd(5).
TERMCAP The string describing the terminal in TERM, or the
name of the termcap file, see termcap(5),
termcap(3).
EXINIT A startup list of commands read by elvis(1).
USER The login name of the user, set by login(1) from the
password file passwd(5).
LOGNAME Set to the same value as USER. BSD derived systems
have USER, System V has LOGNAME, so modern systems
have both to avoid problems.
Further names may be placed in the environment by the
export command and `name=value' arguments in sh(1).
Arguments may also be placed in their environment by
programs if they use putenv(3). Or in the environment
of another program by building a new environment for
one of the exec functions that accepts an environment
list, like execle(2) or execve(2). It is unwise to
conflict with certain sh(1) variables that are fre-
quently set and/or exported by `.profile' files: MAIL,
PS1, PS2, IFS.
SEE ALSO
elvis(1), login(1), sh(1), execl(3), execve(2), system(3),
termcap(3), termcap(5), passwd(5), ttytab(5).