NAME
catopen, catclose - open/close a message catalog
SYNOPSIS
#include <nl_types.h>
nl_catd catopen(const char *name, int flag);
int catclose(nl_catd catalog);
DESCRIPTION
The function catopen() opens a message catalog and returns a catalog
descriptor. The descriptor remains valid until catclose() or
execve(2). If a file descriptor is used to implement catalog
descriptors then the FD_CLOEXEC flag will be set.
The argument name specifies the name of the message catalog to be
opened. If name specifies and absolute path (i.e., contains a '/'),
then name specifies a pathname for the message catalog. Otherwise, the
environment variable NLSPATH is used with name substituted for %N (see
locale(7)). It is unspecified whether NLSPATH will be used when the
process has root privileges. If NLSPATH does not exist in the
environment, or if a message catalog cannot be opened in any of the
paths specified by it, then an implementation defined path is used.
This latter default path may depend on the LC_MESSAGES locale setting
when the flag argument is NL_CAT_LOCALE and on the LANG environment
variable when the flag argument is 0. Changing the LC_MESSAGES part of
the locale may invalidate open catalog descriptors.
The flag argument to catopen() is used to indicate the source for the
language to use. If it is set to NL_CAT_LOCALE then it will use the
current locale setting for LC_MESSAGES. Otherwise it will use the LANG
environment variable.
The function catclose() closes the message catalog identified by
catalog. It invalidates any subsequent references to the message
catalog defined by catalog.
RETURN VALUE
The function catopen() returns a message catalog descriptor of type
nl_catd on success. On failure, it returns (nl_catd) -1 and sets errno
to indicate the error. The possible error values include all possible
values for the open(2) call.
The function catclose() returns 0 on success, or -1 on failure.
ENVIRONMENT
LC_MESSAGES
May be the source of the LC_MESSAGES locale setting, and thus
determine the language to use if flag is set to NL_CAT_LOCALE.
LANG The language to use if flag is 0.
CONFORMING TO
POSIX.1-2001. It is unclear what the source was for the constants
MCLoadBySet and MCLoadAll (see below).
NOTES
The above is the POSIX.1-2001 description. The glibc value for
NL_CAT_LOCALE is 1. (Compare MCLoadAll below.) The default path
varies, but usually looks at a number of places below
/usr/share/locale.
Linux Notes
These functions are available for Linux since libc 4.4.4c. In the case
of linux libc4 and libc5, the catalog descriptor nl_catd is a
mmap(2)’ed area of memory and not a file descriptor. The flag argument
to catopen() should be either MCLoadBySet (=0) or MCLoadAll (=1). The
former value indicates that a set from the catalog is to be loaded when
needed, whereas the latter causes the initial call to catopen() to load
the entire catalog into memory. The default search path varies, but
usually looks at a number of places below /etc/locale and
/usr/lib/locale.
SEE ALSO
catgets(3), setlocale(3)
COLOPHON
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