Chapter 6. LOCALE technology

55

Giving

NULL

for locale will return the current value of the specified locale category. Otherwise,

setlocale()

returns the newly set locale name, or

NULL

for error.

Given

for locale,

setlocale()

will determine the locale name in the following manner:

  At first, consult

LC_ALL

environmental variable.

  If

LC_ALL

is not available, consult environmental variable same as the name of the locale

category. For example,

LC_COLLATE

.

  If none of them are available, consult

LANG

environmental variable.

This is why a user is expected to set

LANG

variable. In other words, all what a user has to do is to

set

LANG

variable so that all locale compliant softwares work well for desired way.

Thus, I recommend strongly to call

setlocale(LC_ALL,   );

at the first of your softwares, if

the softwares are to be international.

6.2 Locale Names

We can specify locale names for these six locale categories. Then, which name should we specify?

The syntax to build a locale name is determined as follows:

language[_territory][.codeset][@modifier]

where language is two lowercase alphabets described in ISO639, such as

en

for English,

eo

for

Esperanto, and

zh

for Chinese, territory is two uppercase alphabets described in ISO3166, such

as

GB

for United Kingdom,

KR

for Republic of Korea (South Korea),

CN

for China. There are

no standard for codeset and modifier. GNU libc uses

ISO 8859 1

,

ISO 8859 13

,

eucJP

,

SJIS

,

UTF8

, and so on for codeset, and

euro

for modifier.

However, it is depend on the system which locale names are valid. In other words, you have to

install locale database for locale you want to use. Type

locale  a

to display all supported locale

names on the system.

Note that locale names of

 C 

and

 POSIX 

are determined for the names for default behav 

ior. For example, when your software need to parse the output of

date(1)

, you'd better call

setlocale(LC_TIME,  C );

before invocation of

date(1)

.