# catopen

## PROLOG



           This manual page is part of the POSIX Programmer's Manual.  The
           Linux implementation of this interface may differ (consult the
           corresponding Linux manual page for details of Linux behavior), or
           the interface may not be implemented on Linux.
    


## NAME



           catopen — open a message catalog
    


## SYNOPSIS



           #include <nl_types.h>
    
           nl_catd catopen(const char *_name_ , int _oflag_);
    


## DESCRIPTION



           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 pathname 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
           POSIX.1‐2017, _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 POSIX.1‐2017, _Section 8.2_ ,
           _Internationalization Variables_).
    


## RETURN VALUE



           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.
    


## ERRORS



           The _catopen_() function may fail if:
    
           **EACCES** Search permission is denied for the component of the path
                  prefix of the message catalog or read permission is denied
                  for the message catalog.
    
           **EMFILE** All file descriptors available to the process are currently
                  open.
    
           **ENAMETOOLONG**
                  The length of a component of a pathname is longer than
                  {NAME_MAX}.
    
           **ENAMETOOLONG**
                  The length of a pathname exceeds {PATH_MAX}, or pathname
                  resolution of a symbolic link produced an intermediate
                  result with a length that exceeds {PATH_MAX}.
    
           **ENFILE** Too many files are currently open in the system.
    
           **ENOENT** The message catalog does not exist or the _name_ argument
                  points to an empty string.
    
           **ENOMEM** Insufficient storage space is available.
    
           **ENOTDIR**
                  A component of the path prefix of the message catalog names
                  an existing file that is neither a directory nor a symbolic
                  link to a directory, or the pathname of the message catalog
                  contains at least one non-<slash> character and ends with
                  one or more trailing <slash> characters and the last
                  pathname component names an existing file that is neither a
                  directory nor a symbolic link to a directory.
    
           _The following sections are informative._
    


## EXAMPLES



           None.
    


## APPLICATION USAGE



           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 developers 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.
    
           To be sure that messages produced by an application running with
           appropriate privileges cannot be used by an attacker setting an
           unexpected value for _NLSPATH_ in the environment to confuse a
           system administrator, such applications should use pathnames
           containing a **'/'** to get defined behavior when using _catopen_() to
           open a message catalog.
    


## RATIONALE



           None.
    


## FUTURE DIRECTIONS



           None.
    


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