Tribblix: manual page: catopen.3c

CATOPEN(3C) Standard C Library Functions CATOPEN(3C)

NAME

catopen, catclose - open/close a message catalog

SYNOPSIS

#include <nl_types.h>

nl_catd catopen(const char *name, int oflag);

int catclose(nl_catd catd);

DESCRIPTION

The catopen() function opens a message catalog and returns a message
catalog descriptor. name specifies the name of the message catalog to
be opened. If name contains a "/", then name specifies a complete
pathname for the message catalog; otherwise, the environment variable
NLSPATH is used and /usr/lib/locale/locale/LC_MESSAGES must exist.
If NLSPATH does not exist in the environment, or if a message catalog
cannot be opened in any of the paths specified by NLSPATH, then the
default path /usr/lib/locale/locale/LC_MESSAGES is used. In the "C"
locale, catopen() will always succeed without checking the default
search path.

The names of message catalogs and their location in the filesystem
can vary from one system to another. Individual applications can
choose to name or locate message catalogs according to their own
special needs. A mechanism is therefore required to specify where the
catalog resides.

The NLSPATH variable provides both the location of message catalogs,
in the form of a search path, and the naming conventions associated
with message catalog files. For example:

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

The metacharacter % introduces a substitution field, where %L
substitutes the current setting of either the LANG environment
variable, if the value of oflag is 0, or the LC_MESSAGES category,
if the value of oflag is NL_CAT_LOCALE, and %N substitutes the
value of the name parameter passed to catopen(). Thus, in the above
example, catopen() will search in /nlslib/$LANG/name.cat, if oflag
is 0, or in /nlslib/{LC_MESSAGES}/name.cat, if oflag is
NL_CAT_LOCALE.

The NLSPATH variable 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.

The full set of metacharacters is:

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

%L
The value of LANG or LC_MESSAGES.

%l
The value of the language element of LANG or LC_MESSAGES.

%t
The value of the territory element of LANG or LC_MESSAGES.

%c
The value of the codeset element of LANG or LC_MESSAGES.

%%
A single %.

The LANG environment variable provides the ability to specify the
user's requirements for native languages, local customs and character
set, as an ASCII string in the form

LANG=language[_territory[.codeset]]

A user who speaks German as it is spoken in Austria and has a
terminal which operates in ISO 8859/1 codeset, would want the setting
of the LANG variable to be

LANG=De_A.88591

With this setting it should be possible for that user to find any
relevant catalogs should they exist.

Should the LANG variable not be set, the value of LC_MESSAGES as
returned by setlocale() is used. If this is NULL, the default path
as defined in <nl_types.h> is used.

A message catalogue descriptor remains valid in a process until that
process closes it, or a successful call to one of the exec functions.
A change in the setting of the LC_MESSAGES category may invalidate
existing open catalogues.

If a file descriptor is used to implement message catalogue
descriptors, the FD_CLOEXEC flag will be set; see <fcntl.h>.

If the value of oflag argument is 0, the LANG environment variable
is used to locate the catalogue without regard to the LC_MESSAGES
category. If the oflag argument is NL_CAT_LOCALE, the LC_MESSAGES
category is used to locate the message catalogue.

The catclose() function closes the message catalog identified by
catd. If a file descriptor is used to implement the type nl_catd,
that file descriptor will be closed.

RETURN VALUES

Upon successful completion, catopen() returns a message catalog
descriptor for use on subsequent calls to catgets() and catclose().
Otherwise it returns (nl_catd) -1.

Upon successful completion, catclose() returns 0. Otherwise it
returns -1 and sets errno to indicate the error.

ERRORS

The catopen() function may fail if:

EACCES
Search permission is denied for the component of the
path prefix of the message catalogue or read
permission is denied for the message catalogue.

EMFILE
There are OPEN_MAX file descriptors currently open in
the calling process.

ENAMETOOLONG
The length of the pathname of the message catalogue
exceeds PATH_MAX, or a pathname component is longer
than NAME_MAX.

ENAMETOOLONG
Pathname resolution of a symbolic link produced an
intermediate result whose length exceeds PATH_MAX.

ENFILE
Too many files are currently open in the system.

ENOENT
The message catalogue does not exist or the name
argument points to an empty string.

ENOMEM
Insufficient storage space is available.

ENOTDIR
A component of the path prefix of the message
catalogue is not a directory.

The catclose() function may fail if:

EBADF
The catalogue descriptor is not valid.

EINTR
The catclose() function was interrupted by a signal.

USAGE

The catopen() and catclose() functions can be used safely in
multithreaded applications, as long as setlocale(3C) is not being
called to change the locale.

ATTRIBUTES