man-pages/man3/catopen.3

.\" Copyright 1993 Mitchum DSouza <m.dsouza@mrc-applied-psychology.cambridge.ac.uk>
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.\" Modified Thu Dec 13 22:51:19 2001 by Martin Schulze <joey@infodrom.org>
.\" Modified 2001-12-14 aeb
.\"
.TH CATOPEN 3 2021-03-22 "GNU" "Linux Programmer's Manual"
.SH NAME
catopen, catclose \- open/close a message catalog
.SH SYNOPSIS
.nf
.B #include <nl_types.h>
.PP
.BI "nl_catd catopen(const char *" name ", int " flag );
.BI "int catclose(nl_catd " catalog );
.fi
.SH DESCRIPTION
The function
.BR catopen ()
opens a message catalog and returns a catalog descriptor.
The descriptor remains valid until
.BR catclose ()
or
.BR execve (2).
If a file descriptor is used to implement catalog descriptors,
then the
.B FD_CLOEXEC
flag will be set.
.PP
The argument
.I name
specifies the name of the message catalog to be opened.
If
.I name
specifies an absolute path (i.e., contains a \(aq/\(aq),
then
.I name
specifies a pathname for the message catalog.
Otherwise, the environment variable
.B NLSPATH
is used with
.I name
substituted for
.B %N
(see
.BR locale (7)).
It is unspecified whether
.B NLSPATH
will be used when the process has root privileges.
If
.B 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
.B LC_MESSAGES
locale setting when the
.I flag
argument is
.B NL_CAT_LOCALE
and on the
.B LANG
environment variable when the
.I flag
argument is 0.
Changing the
.B LC_MESSAGES
part of the locale may invalidate
open catalog descriptors.
.PP
The
.I flag
argument to
.BR catopen ()
is used to indicate the source for the language to use.
If it is set to
.BR NL_CAT_LOCALE ,
then it will use the current locale setting for
.BR LC_MESSAGES .
Otherwise, it will use the
.B LANG
environment variable.
.PP
The function
.BR catclose ()
closes the message catalog identified by
.IR catalog .
It invalidates any subsequent references to the message catalog
defined by
.IR catalog .
.SH RETURN VALUE
The function
.BR catopen ()
returns a message catalog descriptor of type
.I nl_catd
on success.
On failure, it returns
.IR "(nl_catd)\ \-1"
and sets
.I errno
to indicate the error.
The possible error values include all
possible values for the
.BR open (2)
call.
.PP
The function
.BR catclose ()
returns 0 on success, or \-1 on failure.
.SH ENVIRONMENT
.TP
.B LC_MESSAGES
May be the source of the
.B LC_MESSAGES
locale setting, and thus
determine the language to use if
.I flag
is set to
.BR NL_CAT_LOCALE .
.TP
.B LANG
The language to use if
.I flag
is 0.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.ad l
.nh
.TS
allbox;
lbx lb lb
l l l.
Interface	Attribute	Value
T{
.BR catopen ()
T}	Thread safety	MT-Safe env
T{
.BR catclose ()
T}	Thread safety	MT-Safe
.TE
.hy
.ad
.sp 1
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.\" In XPG 1987, Vol. 3 it says:
.\" .I "The flag argument of catopen is reserved for future use"
.\" .IR "and should be set to 0" .
.\"
.\" It is unclear what the source was for the constants
.\" .B MCLoadBySet
.\" and
.\" .B MCLoadAll
.\" (see below).
.SH NOTES
The above is the POSIX.1 description.
The glibc value for
.B NL_CAT_LOCALE
is 1.
.\" (Compare
.\" .B MCLoadAll
.\" below.)
The default path varies, but usually looks at a number of places below
.IR /usr/share/locale .
.\" .SS Linux notes
.\" These functions are available for Linux since libc 4.4.4c.
.\" In the case of linux libc4 and libc5, the catalog descriptor
.\" .I nl_catd
.\" is a
.\" .BR mmap (2)'ed
.\" area of memory and not a file descriptor.
.\" The
.\" .I flag
.\" argument to
.\" .BR catopen ()
.\" should be either
.\" .B MCLoadBySet
.\" (=0) or
.\" .B 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
.\" .BR catopen ()
.\" to load the entire catalog into memory.
.\" The default search path varies, but usually looks at a number of places below
.\" .I /etc/locale
.\" and
.\" .IR /usr/lib/locale .
.SH SEE ALSO
.BR catgets (3),
.BR setlocale (3)