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(5).
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(5).
LANG
The string used to specify internationalization
information that allows users to work with different national conventions. The
setlocale(3C) and
newlocale(3C) functions check the
LANG
environment variable when they are 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. In addition, some commands will use uselocale(3C) to set a
thread-specific locale.
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
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.
The value of
TZ has one of the two formats (spaces inserted for
clarity):
:characters
or
std offset dst offset, rule
If TZ is of the first format (that is, if the first
character is a colon (:)), or if TZ is not of the second format, then
TZ designates a path to a timezone database file relative to
/usr/share/lib/zoneinfo/, ignoring a leading colon if one exists.
Otherwise, TZ is of the second form, which when expanded is
as follows:
stdoffset[dst[offset][,start[/time],end[/time]]]
std and dst
Indicate no less than three, nor more than
{
TZNAME_MAX}, bytes that are the designation for the standard
(
std) or the alternative (
dst, such as Daylight Savings Time)
timezone. Only
std is required; if
dst is missing, then the
alternative time does not apply in this timezone. Each of these fields can
occur in either of two formats, quoted or unquoted:
- o
- In the quoted form, the first character is the less-than ('<')
character and the last character is the greater-than ('>') character.
All characters between these quoting characters are alphanumeric
characters from the portable character set in the current locale, the
plus-sign ('+') character, or the minus-sign ('-') character. The
std and dst fields in this case do not include the quoting
characters.
- o
- In the unquoted form, all characters in these fields are alphabetic
characters from the portable character set in the current locale.
The interpretation of these fields is unspecified if either field is less than
three bytes (except for the case when
dst is missing), more than
{
TZNAME_MAX} bytes, or if they contain characters other than those
specified.
offset
Indicate 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 can 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 can 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 can cause
unpredictable behavior. If preceded by a "-", the timezone is east
of the Prime Meridian. Otherwise, it is west of the Prime Meridian (which
can 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 occurs. 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 specified.
The time has the same format as offset except that
no leading sign ("-" or "+" ) is allowed. If time
is not specified, the default value is 02:00:00.