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


catopen, catclose - open/close a message catalog


#include <nl_types.h>

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

int catclose(nl_catd catd);


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:


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/, if oflag is 0, or in
/nlslib/{LC_MESSAGES}/, 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:

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

The value of LANG or LC_MESSAGES.

The value of the language element of LANG or LC_MESSAGES.

The value of the territory element of LANG or LC_MESSAGES.

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


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


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.


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.


The catopen() function may fail if:

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

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

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

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

Too many files are currently open in the system.

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

Insufficient storage space is available.

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

The catclose() function may fail if:

The catalogue descriptor is not valid.

The catclose() function was interrupted by a signal.


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.


See attributes(7) for descriptions of the following attributes:

|Interface Stability | Standard |
|MT-Level | MT-Safe |


gencat(1), catgets(3C), gettext(3C), setlocale(3C), nl_types.h(3HEAD),
attributes(7), environ(7)

December 29, 1996 CATOPEN(3C)