When a process begins execution, one of the exec family of functions makes available an array of strings called the environment; see exec(2). By convention, these strings have the form variable=value, for example, PATH=/sbin:/usr/sbin. These environmental variables provide a way to make information about a program's environment available to programs.

A name may be placed in the environment by the export command and name=value arguments in sh(1), or by one of the exec functions. It is unwise to conflict with certain shell variables such as MAIL, PS1, PS2, and IFS that are frequently exported by .profile files; see profile(4).

The following environmental variables can be used by applications and are expected to be set in the target run-time environment.

HOME

The name of the user's login directory, set by login(1) from the password file; see passwd(4).

LANG

The string used to specify internationalization information that allows users to work with different national conventions. The setlocale(3C) function checks the LANG environment variable when it is called with "" as the locale argument. LANG is used as the default locale if the corresponding environment variable for a particular category is unset or null. If, however, LC_ALL is set to a valid, non-empty value, its contents are used to override both the LANG and the other LC_* variables. For example, when invoked as setlocale(LC_CTYPE, ""), setlocale() will query the LC_CTYPE environment variable first to see if it is set and non-null. If LC_CTYPE is not set or null, then setlocale() will check the LANG environment variable to see if it is set and non-null. If both LANG and LC_CTYPE are unset or NULL, the default "C" locale will be used to set the LC_CTYPE category.

Most commands will invoke setlocale(LC_ALL, "") prior to any other processing. This allows the command to be used with different national conventions by setting the appropriate environment variables.

The following environment variables correspond to each category of setlocale(3C):

LC_ALL

If set to a valid, non-empty string value, override the values of LANG and all the other LC_*variables.

LC_COLLATE

This category specifies the character collation sequence being used. The information corresponding to this category is stored in a database created by the localedef(1) command. This environment variable affects strcoll(3C) and strxfrm(3C).

LC_CTYPE

This category specifies character classification, character conversion, and widths of multibyte characters. When LC_CTYPE is set to a valid value, the calling utility can display and handle text and file names containing valid characters for that locale; Extended Unix Code (EUC) characters where any individual character can be 1, 2, or 3 bytes wide; and EUC characters of 1, 2, or 3 column widths. The default "C" locale corresponds to the 7-bit ASCII character set; only characters from ISO 8859-1 are valid. The information corresponding to this category is stored in a database created by the localedef() command. This environment variable is used by ctype(3C), mblen(3C), and many commands, such as cat(1), ed(1), ls(1), and vi(1).

LC_MESSAGES

This category specifies the language of the message database being used. For example, an application may have one message database with French messages, and another database with German messages. Message databases are created by the mkmsgs(1) command. This environment variable is used by exstr(1), gettxt(1), srchtxt(1), gettxt(3C), and gettext(3C).

LC_MONETARY

This category specifies the monetary symbols and delimiters used for a particular locale. The information corresponding to this category is stored in a database created by the localedef(1) command. This environment variable is used by localeconv(3C).

LC_NUMERIC

This category specifies the decimal and thousands delimiters. The information corresponding to this category is stored in a database created by the localedef() command. The default C locale corresponds to "." as the decimal delimiter and no thousands delimiter. This environment variable is used by localeconv(3C), printf(3C), and strtod(3C).

LC_TIME

This category specifies date and time formats. The information corresponding to this category is stored in a database specified in localedef(). The default C locale corresponds to U.S. date and time formats. This environment variable is used by many commands and functions; for example: at(1), calendar(1), date(1), strftime(3C), and getdate(3C).

MSGVERB

Controls which standard format message components fmtmsg selects when messages are displayed to stderr; see fmtmsg(1) and fmtmsg(3C).

NETPATH

A colon-separated list of network identifiers. A network identifier is a character string used by the Network Selection component of the system to provide application-specific default network search paths. A network identifier must consist of non-null characters and must have a length of at least 1. No maximum length is specified. Network identifiers are normally chosen by the system administrator. A network identifier is also the first field in any /etc/netconfig file entry. NETPATH thus provides a link into the /etc/netconfig file and the information about a network contained in that network's entry. /etc/netconfig is maintained by the system administrator. The library routines described in getnetpath(3NSL) access the NETPATH environment variable.

NLSPATH

Contains a sequence of templates which catopen(3C) and gettext(3C) use when attempting to locate message catalogs. Each template consists of an optional prefix, one or more substitution fields, a filename and an optional suffix. For example:

NLSPATH="/system/nlslib/%N.cat"

defines that catopen() should look for all message catalogs in the directory /system/nlslib, where the catalog name should be constructed from the name parameter passed to catopen(), %N, with the suffix .cat.

Substitution fields consist of a % symbol, followed by a single-letter keyword. The following keywords are currently defined:

%N

The value of the name parameter passed to catopen().

%L

The value of LANG or LC_MESSAGES.

%l

The language element from LANG or LC_MESSAGES.

%t

The territory element from LANG or LC_MESSAGES.

%c

The codeset element from LANG or LC_MESSAGES.

%%

A single % character.

An empty string is substituted if the specified value is not currently defined. The separators "_" and "." are not included in %t and %c substitutions.

Templates defined in NLSPATH are separated by colons (:). A leading colon or two adjacent colons (::) is equivalent to specifying %N. For example:

NLSPATH=":%N.cat:/nlslib/%L/%N.cat"

indicates to catopen() that it should look for the requested message catalog in name, name.cat and /nlslib/$LANG/name.cat. For gettext(), %N automatically maps to "messages".

If NLSPATH is unset or NULL, catopen() and gettext() call setlocale(3C), which checks LANG and the LC_* variables to locate the message catalogs.

NLSPATH will normally be set up on a system wide basis (in /etc/profile) and thus makes the location and naming conventions associated with message catalogs transparent to both programs and users.

PATH

The sequence of directory prefixes that sh(1), time(1), nice(1), nohup(1), and other utilities apply in searching for a file known by an incomplete path name. The prefixes are separated by colons (:). login(1) sets PATH=/usr/bin. For more detail, see sh(1).

SEV_LEVEL

Define severity levels and associate and print strings with them in standard format error messages; see addseverity(3C), fmtmsg(1), and fmtmsg(3C).

TERM

The kind of terminal for which output is to be prepared. This information is used by commands, such as vi(1), which may exploit special capabilities of that terminal.

TZ

Timezone information. The contents of this environment variable are used by the functions ctime(3C), localtime(3C), strftime(3C), and mktime(3C) to override the default timezone. If TZ is not in the following form, it designates a path to a timezone database file relative to /usr/share/lib/zoneinfo/, ignoring the first character if it is a colon (:). Otherwise, TZ has the form:

stdoffset[dst[offset][,start[/time],end[/time]]]

std and dst

Three or more bytes that are the designation for the standard (std) and daylight savings time (dst) timezones. Only std is required. If dst is missing, then daylight savings time does not apply in this locale. Upper- and lower-case letters from the portable character set are explicitly allowed. Any graphic characters from the portable character set except a leading colon (:) or digits, the comma (,), the minus (-), the plus (+), and the null character are permitted to appear in these fields, but their meaning is unspecified.

offset

Indicates the value one must add to the local time to arrive at Coordinated Universal Time. The offset has the form:

hh[:mm[:ss]]

The minutes (mm) and seconds (ss) are optional. The hour (hh) is required and may be a single digit. The offset following std is required. If no offset follows dst , daylight savings time is assumed to be one hour ahead of standard time. One or more digits may be used. The value is always interpreted as a decimal number. The hour must be between 0 and 24, and the minutes (and seconds), if present, must be between 0 and 59. Out of range values may cause unpredictable behavior. If preceded by a "-", the timezone is east of the Prime Meridian. Otherwise, it is west of the Prime Meridian (which may be indicated by an optional preceding "+" sign).

start/time,end/time

Indicate when to change to and back from daylight savings time, where start/time describes when the change from standard time to daylight savings time occurs, and end/time describes when the change back happens. Each time field describes when, in current local time, the change is made.

The formats of start and end are one of the following:

Jn

The Julian day n (1 <= n <= 365). Leap days are not counted. That is, in all years, February 28 is day 59 and March 1 is day 60. It is impossible to refer to the occasional February 29.

n

The zero-based Julian day (0 <= n <= 365). Leap days are counted, and it is possible to refer to February 29.

Mm.n.d

The d^th day, (0 <= d <= 6) of week n of month m of the year (1 <= n <= 5, 1 <= m <= 12), where week 5 means "the last d-day in month m" which may occur in either the fourth or the fifth week). Week 1 is the first week in which the d^th day occurs. Day zero is Sunday.

Implementation specific defaults are used for start and end if these optional fields are not given.

The time has the same format as offset except that no leading sign ("-" or "+" is allowed. The default, if time is not given is 02:00:00.

cat(1), date(1), ed(1), fmtmsg(1), localedef(1), login(1), ls(1), mkmsgs(1), nice(1), nohup(1), sh(1), sort(1), time(1), vi(1), exec(2), addseverity(3C), catopen(3C), ctime(3C), ctype(3C), fmtmsg(3C), getdate(3C), getnetpath(3NSL), gettext(3C), gettxt(3C), localeconv(3C), mblen(3C), mktime(3C), printf(3C), setlocale(3C), strcoll(3C), strftime(3C), strtod(3C), strxfrm(3C), TIMEZONE(4), netconfig(4), passwd(4), profile(4)