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Manual Pages  — ENVIRON


environ – user environment



extern char **environ;


An array of strings, called the environment is made available to each process by execve(2) when a process begins. By convention these strings have the form name=value, and are referred to as "environment variables". A process can query, update, and delete these strings using the getenv(3), setenv(3), and unsetenv(3) functions, respectively. The shells also provide commands to manipulate the environment; they are described in the respective shell manual pages.

What follows is a list of environment variables typically seen on a Unix system. It includes only those variables that a user can expect to see during their day-to-day use of the system, and is far from complete. Environment variables specific to a particular program or library function are documented in the ENVIRONMENT section of the appropriate manual page.


BLOCKSIZE The size of the block units used by several disk-related 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. 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_COLLATE Locale to be used for ordering of strings.
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.
MANPATH The sequence of directories, separated by colons, searched by man(1) when looking for manual pages.
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).
  When set to any value, this environment variable modifies the behaviour of certain commands to (mostly) execute in a strictly POSIX-compliant manner.
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. It is recommended that portable applications use LOGNAME instead.

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).


cd(1), csh(1), env(1), ex(1), login(1), printenv(1), sh(1), execve(2), execle(3), getbsize(3), getenv(3), setenv(3), setlocale(3), system(3), termcap(3), termcap(5)


The environ manual page appeared in AT&T v7 .

ENVIRON (7) August 5, 2020

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