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
See
attributes(7) for descriptions of the following attributes:
+--------------------+-----------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-----------------+
|Interface Stability | Standard |
+--------------------+-----------------+
|MT-Level | MT-Safe |
+--------------------+-----------------+
SEE ALSO
gencat(1),
catgets(3C),
gettext(3C),
setlocale(3C),
nl_types.h(3HEAD),
attributes(7),
environ(7) December 29, 1996
CATOPEN(3C)