ENVIRON(7) BSD Miscellaneous Information Manual ENVIRON(7)NAMEenviron — 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 appli‐
cations use either “/tmp” or “/var/tmp”. Setting this vari‐
able 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 fre‐
quently 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 rou‐
tines 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 rou‐
tines.
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 run‐
time.
SEE ALSOcsh(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.
4.2 Berkeley Distribution April 19, 1994 4.2 Berkeley Distribution
