nl_catd catopen(const char *name, int oflag);
The catopen() function shall open a message catalog and return a message catalog descriptor. The name argument specifies the name of the message catalog to be opened. If name contains a '/' , then name specifies a complete name for the message catalog. Otherwise, the environment variable NLSPATH is used with name substituted for the %N conversion specification (see the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 8, Environment Variables). If NLSPATH exists in the environment when the process starts, then if the process has appropriate privileges, the behavior of catopen() is undefined. If NLSPATH does not exist in the environment, or if a message catalog cannot be found in any of the components specified by NLSPATH, then an implementation-defined default path shall be used. This default may be affected by the setting of LC_MESSAGES if the value of oflag is NL_CAT_LOCALE, or the LANG environment variable if oflag is 0.
A message catalog descriptor shall remain 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 catalogs.
If a file descriptor is used to implement message catalog descriptors, the FD_CLOEXEC flag shall be set; see <fcntl.h>.
If the value of the oflag argument is 0, the LANG environment variable is used to locate the catalog 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 catalog (see the Base Definitions volume of IEEE Std 1003.1-2001, Section 8.2, Internationalization Variables).
Upon successful completion, catopen() shall return a message catalog descriptor for use on subsequent calls to catgets() and catclose(). Otherwise, catopen() shall return ( nl_catd) -1 and set errno to indicate the error.
The catopen() function may fail if:
The following sections are informative.
Some implementations of catopen() use malloc() to allocate space for internal buffer areas. The catopen() function may fail if there is insufficient storage space available to accommodate these buffers.
Conforming applications must assume that message catalog descriptors are not valid after a call to one of the exec functions.
Application writers should be aware that guidelines for the location of message catalogs have not yet been developed. Therefore they should take care to avoid conflicting with catalogs used by other applications and the standard utilities.
catclose() , catgets() , the Base Definitions volume of IEEE Std 1003.1-2001, <fcntl.h>, <nl_types.h>, the Shell and Utilities volume of IEEE Std 1003.1-2001