environment File

Purpose

Sets up the user environment.

Description

The /etc/environment file contains variables specifying the basic environment for all processes. When a new process begins, the exec subroutine makes an array of strings available that have the form Name=Value. This array of strings is called the environment. Each name defined by one of the strings is called an environment variable or shell variable. The exec subroutine allows the entire environment to be set at one time.

Environment variables are examined when a command starts running. The environment of a process is not changed by altering the /etc/environment file. Any processes that were started prior to the change to the /etc/environment file must be restarted if the change is to take effect for those processes. If the TZ variable is changed, the cron daemon must be restarted, because this variable is used to determine the current local time.

The following restrictions apply, when modifying the environment file:

Ensure that newly created environment variables do not conflict with standard variables such as MAIL, PS1, PS2, and IFS.
Ensure that the information in the environment file is in the Name=Value format. Unlike profile scripts, the environment file is not a shell script and does not accept data in any format other than the Name=Value format.

The Basic Environment

When you log in, the system sets environment variables from the environment file before reading your login profile, .profile.

The following variables make up the basic environment:

Variable	Description
HOME	The full path name of the user login or HOME directory. The login program sets this to the name specified in the /etc/passwd file.
LANG	The locale name currently in effect. The LANG variable is set in the /etc/environment file at installation time.
NLSPATH	The full path name for message catalogs. The default is: /usr/lib/nls/msg/%L/%N: /usr/lib/nls/msg/%L/%N.cat: where %L is the value of the LC_MESSAGES category and %N is the catalog file name. Note: See the chlang command for more information about changing message catalogs.
LC__FASTMSG	If LC_FASTMEG is set to false, POSIX-compliant message handling is performed. If LC__FASTMSG is set to true, it specifies that default messages should be used for the C and POSIX locales and that NLSPATH is ignored. If this variable is set to anything other than false or unset, it is considered the same as being set to true. The default value is LC__FASTMSG=true in the /etc/environment file.
LOCPATH	The full path name of the location of National Language Support tables. The default is /usr/lib/nls/loc and is set in the /etc/profile file. If the LOCPATH variable is a null value, it assumes that the current directory contains the locale files. Note: All setuid and setgid programs will ignore the LOCPATH environment variable.
PATH	The sequence of directories that commands such as the sh, time, nice and nohup commands search when looking for a command whose path name is incomplete. The directory names are separated by colons.
TZ	The time-zone information. The TZ environment variable is set by the /etc/environment file. The TZ environment variable has the following format (spaces inserted for readability): `std offset dst offset , rule` The fields within the TZ environment variable are defined as follows: std and dst Designate the standard (std) and summer (dst) time zones. Only the std value along with the appropriate offset value is required. If the dst value is not specified, summer time does not apply. The values specified may be no less than three and no more than TZNAME_MAX bytes in length. The length of the variables corresponds to the `%Z` field of the date command; for libc and libbsd, TZNAME_MAX equals three characters. Any nonnumeric ASCII characters except the following may be entered into each field: a leading : (colon), a , (comma), a - (minus sign), a + (plus sign), or the ASCII null character. Note: POSIX 1.0 reserves the leading : (colon) for an implementation-defined TZ specification. The operating system disallows the leading colon, selecting CUT0 and setting the `%Z` field to a null string. An example of std and dst format is as follows: `EST5EDT` Note: If the value set is invalid or unrecognized, the time zone defaults to UTC/GMT.
`EST`	Specifies Eastern U.S. standard time.
`5`	Specifies the offset, which is 5 hours behind Coordinated Universal Time (CUT). `EDT` Specifies the corresponding summer time zone abbreviation. Note: See "Time Zones" for a list of time zone names defined for the system. offset Denotes the value added to local time to equal Coordinated Universal Time (CUT). CUT is the international time standard that has largely replaced Greenwich Mean Time. The offset variable has the following format: `hh:mm:ss` The fields within the offset variable are defined as follows:
`hh`	Specifies the dst offset in hours. This field is required. The `hh` value can range between the integers -12 and +11. A negative value indicates the time zone is east of the prime meridian; a positive value or no value indicates the time zone is west of the prime meridian.
`mm`	Specifies the dst offset detailed to the minute. This field is optional. If the `mm` value is present, it must be specified between 0 and 59 and preceded by a : (colon). `ss` Specifies the dst offset detailed to the second. The `ss` field is optional. If the `ss` value is present, it must be specified between 0 and 59 and preceded by a : (colon). An offset variable must be specified with the std variable. An offset variable for the dst variable is optional. If no offset is specified with the dst variable, the system assumes that summer time is one hour ahead of standard time. As an example of offset syntax, Zurich is one hour ahead of CUT, so its offset is -1. Newfoundland is 1.5 hours ahead of eastern U.S. standard time zones. Its syntax can be stated as any of the following: 3:30, 03:30, +3:30, or 3:30:00. rule The rule variable indicates when to change to and back from summer time. The rule variable has the following format: `start/time,end/time` The fields within the rule variable are defined as follows:
`start`	Specifies the change from standard to summer time.
`end`	Specifies the return to standard time from summer time.
`time`	Specifies when the time changes occur within the time zone. For example, if the `time` variable is encoded for 2 a.m. then the time changes when the time zone reaches 2 a.m. on the date specified in the `start` variable.
`/`	Delimits the start date, end date, and time variables. `,` (Comma) Delimits two date and time pairs. The `start` and `end` variables support a syntax for Julian time (`J`) and a syntax for leap years (`M`): `Jn Mm.n.d` In the `J` syntax, the `n` variable has the value of 1 through 365. Leap days are not counted. In the `M` syntax, `m` is the month, `n` the week, and `d` the day of the week starting from day 0 (Sunday). The rule variable has the same format as the offset variable except no leading - (minus sign) or + (plus sign) is allowed. The default of the `start` variable is 02:00:00 (2 a.m.). Note: The time zone offsets and time change points are interrelated and context-dependent. The rule variable's runtime execution semantics change as a function of the offsets. For example, if the summer time zone changes one hour, as in `CST6CDT5`, (the default 2 a.m.) summer time changes instantaneously from 2 a.m. to 3 a.m. CDT. The fall change is from 2 a.m. CDT to 1 a.m. CST. The respective changes for a time zone of `CST6CDT4` are 2 a.m. CST to 4 a.m. CDT and 2 a.m. CDT to 12 a.m. CST. In an example of the rule variable, if the law changed so that the Central United States experienced summer time between Julian 129 and Julian 131, the TZ variable would be stated as follows: `TZ=CST6CDT5,J129,J131` In this example, the dates indicated are May 09 and May 11,1993, respectively. (Use the date +%j command to get the Julian date number.) In another example, if the time changes were to occur at 2 a.m. CST and 19:30 CDT, respectively, the variables would be stated as follows: `TZ=CST6CDT5,J129,J131/19:30` In nonleap years, the fallback time change would be from 19:30 CDT to 18:30 CST on May 11 (1993). For the leap year (`M`) syntax, the spring ahead date would be 2 May and the fallback date is 9 May. The variables are stated as follows: `TZ=CST6CDT5,M5.1.0,M5.2.0`

Time Zones

The system defines the following time zones and time zone names:

Note: Coordinated Universal Time (CUT) is the international time standard.

Table 1. Time Zones Defined on the System
Name	Time Zone	CUT Offset
CUT0GDT	Coordinated Universal Time	CUT
GMT0BST	United Kingdom	CUT
WET0WEST	Western Europe	CUT
AZOREST1AZOREDT	Azores, Cape Verde	CUT -1
FALKST2FALKDT	Falkland Islands	CUT -2
GRNLNDST3GRNLNDDT	Greenland, East Brazil	CUT -3
AST4ADT	Central Brazil	CUT -4
EST5EDT	Eastern United States, Colombia	CUT -4
CST6CDT	Central United States, Honduras	CUT -6
MST7MDT	Mountain United States	CUT -7
PST8PDT	Pacific United States, Yukon	CUT -8
AST9ADT	Alaska	CUT -9
HST10HDT	Hawaii, Aleutian Islands	CUT -10
BST11BDT	Bering Strait	CUT -11
NZST-12NZDT	New Zealand	CUT +12

Item	Description
MET-11METDT	Solomon Islands	CUT +11
EET-10EETDT	Eastern Australia	CUT +10
JST-9JSTDT	Japan	CUT +9
KORST-9KORDT	Korea	CUT +9
WAUST-8WAUDT	Western Australia	CUT +8
TAIST-8TAIDT	Taiwan	CUT +8
THAIST-7THAIDT	Thailand	CUT +7
TASHST-6TASHDT	Central Asia	CUT +6
PAKST-5PAKDT	Pakistan	CUT +5
WST-4WDT	Gorki, Central Asia, Oman	CUT +4
MEST-3MEDT	Turkey	CUT +3
SAUST-3SAUDT	Saudi Arabia	CUT +3
EET-2EEST	Eastern Europe	CUT +2
USAST-2USADT	South Africa	CUT +2
CET-1CEST	Central Europe	CUT +1

Files

Item	Description
/etc/profile	Specifies variables to be added to the environment by the shell.
/etc/environment	Specifies the basic environment for all processes.
$HOME/.profile	Specifies the environment for specific user needs.
/etc/passwd	Specifies user IDs.