catopen, catclose — open/close a message catalog
#include <nl_types.h>
nl_catd catopen( |
const char * | name, |
| int | flag); |
int
catclose( |
nl_catd | catalog); |
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.
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.
LC_MESSAGESMay be the source of the LC_MESSAGES locale setting, and thus
determine the language to use if flag is set to
NL_CAT_LOCALE.
LANGThe language to use if flag is 0.
POSIX.1-2001. It is unclear what the source was for the
constants MCLoadBySet and
MCLoadAll (see below).
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.
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.