ENVIRON(7) Miscellaneous Information Manual 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). This variable is processed
by the getbsize(3) function.
COLUMNS The user's preferred width in column positions for the
terminal. Utilities such as ls(1) and who(1) use this to
format output into columns. If unset or empty, utilities
will use an ioctl(2) call to ask the terminal driver for the
width.
EDITOR Default editor name.
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).
LANG This variable configures all programs which use setlocale(3)
to use the specified locale unless the LC_* variables are
set.
LC_ALL Overrides the values of LC_COLLATE, LC_CTYPE, LC_MESSAGES,
LC_MONETARY, LC_NUMERIC, LC_TIME and LANG.
LC_COLLATE Locale to be used for ordering of characters. Note that
this may also affect character ranges in regex(3), e.g.,
“[A-Z]” may include characters that “[[:upper:]]” would not,
depending on how the specified locale orders characters.
LC_CTYPE Locale to be used for character classification (letter,
space, digit, etc.) and for interpreting byte sequences as
multibyte characters.
LC_MESSAGES Locale to be used for diagnostic messages.
LC_MONETARY Locale to be used for interpreting monetary input and
formatting output.
LC_NUMERIC Locale to be used for interpreting numeric input and
formatting output.
LC_TIME Locale to be used for interpreting dates input and for
formatting output.
MAIL The location of the user's mailbox instead of the default in
/var/mail, used by mail(1), sh(1), and many other mail
clients.
NLSPATH List of directories to be searched for the message catalog
referred to by LC_MESSAGES. See catopen(3).
PAGER Default paginator program. The program specified by this
variable is used by mail(1), man(1), ftp(1), etc, to display
information which is longer than the current display.
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).
PWD The current directory pathname.
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) or
plot(1) which may exploit special terminal capabilities.
See /usr/share/misc/termcap (termcap(5)) for a list of
terminal types.
TERMCAP The string describing the terminal in TERM, or, if it begins
with a '/', the name of the termcap file. See TERMPATH
below, and termcap(5).
TERMPATH A sequence of pathnames of termcap files, separated by
colons or spaces, which are searched for terminal
descriptions in the order listed. Having no TERMPATH is
equivalent to a TERMPATH of “$HOME/.termcap:/etc/termcap”.
TERMPATH is ignored if TERMCAP contains a full pathname.
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=America/Los_Angeles date”
displays the current time in California. See tzset(3) for
more information.
USER The login name of the user.
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.
The current environment variables can be printed with env(1), set(1) or
printenv(1) in sh(1) and env(1), printenv(1) or the printenv built-in
command in csh(1).
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
cd(1), csh(1), env(1), ex(1), login(1), printenv(1), sh(1), execve(2),
execle(3), getenv(3), putenv(3), setenv(3), unsetenv(3), setlocale(3),
system(3), termcap(3), termcap(5)
HISTORY
The environ manual page appeared in 4.2BSD.
macOS 15.2 April 12, 2003 macOS 15.2