ENVIRON(7)

NAME
environ - user environment

SYNOPSIS
extern char **environ;

DESCRIPTION
An array of strings called the environment is made available by execve(2) when a process begins. By convention these strings have the form “name=value”. The following names are used by various commands:

BLOCKSIZE
    The size of the block units used by several commands, most notably df(1), du(1) and ls(1). BLOCKSIZE may be specified in units of a byte by specifying a number, in units of a kilobyte by specifying a number followed by ``K'' or ``k'', in units of a megabyte by specifying a number followed by ``M'' or ``m'' and in units of a gigabyte by specifying a number followed by ``G'' or ``g''. Sizes less than 512 bytes or greater than a gigabyte are ignored.

EXINIT
    A startup list of commands read by ex(1) and vi(1).

HOME
    A user's login directory, set by login(1) from the password file passwd(5).

PATH
    The sequence of directories, separated by colons, searched by csh(1), sh(1), system(3), execvp(3), etc, when looking for an executable file. PATH is set to ``/usr/bin:/bin'' initially by login(1).

PRINTER
    The name of the default printer to be used by lpr(1), lpq(1), and lprm(1).

SHELL
    The full pathname of the user's login shell.

TERM
    The kind of terminal for which output is to be prepared. This information is used by commands, such as nroff(1) which may exploit special terminal capabilities. See termcap(3) and terminfo(5).

TMPDIR
    The directory in which to store temporary files. Most applications use either “/tmp” or “/var/tmp”. Setting this variable will make them use another directory.

TZ  The timezone to use when displaying dates. The normal format is a pathname relative to “/usr/share/zoneinfo”. For example, the command “env TZ=US/Pacific date” displays the current time in California. See tzset(3) for more information.

LOGNAME
    The login name of the user.

USER
    Deprecated synonym of LOGNAME (for backwards compatibility).

Further names may be placed in the environment by the export command and name=value arguments in sh(1), or by the setenv command if you use csh(1). It is unwise to change certain sh(1) variables that are frequently exported by .profile files, such as MAIL, PS1, PS2, and IFS, unless you know what you are doing.

PROGRAMMING
Programs can query and modify the environment, using the environment routines getenv(3), putenv(3), setenv(3) and unsetenv(3). Direct access can be made through the global variable environ, though it is recommended that changes to the enviroment still be made through the environment routines.

Shared libraries and bundles don't have direct access to environ, which is only available to the loader ld(1) when a complete program is being linked. The environment routines can still be used, but if direct access to environ is needed, the _NSGetEnviron() routine, defined in <crt_externs.h>, can be used to retrieve the address of environ at runtime.

SEE ALSO
csh(1), ex(1), login(1), sh(1), getenv(3), putenv(3), setenv(3), unsetenv(3), execve(2), execle(3), system(3), termcap(3), terminfo(5)

HISTORY
The environ manual page appeared in 4.2BSD.