get_mfield_list_by_type (3) - Linux Manuals

get_mfield_list_by_type: retrieve a list of fields in a dirfile


get_mfield_list_by_type --- retrieve a list of fields in a dirfile


#include <getdata.h>
const char **get_mfield_list_by_type(DIRFILE *dirfile, const char *parent, gd_entype_t type);


The get_mfield_list_by_type() function queries a dirfile(5) database specified by dirfile and returns a read-only list of names of the all metafields of the indicated type for the supplied parent field.

The dirfile argument must point to a valid DIRFILE object previously created by a call to dirfile_open(3). The type argument should be one of the following symbols indicating the desired field type:


The array returned will be de-allocated by a call to dirfile_close(3) and should not be de-allocated by the caller. The list returned should not be assumed to be in any particular order. The array is terminated by a NULL pointer. The number of fields in the array can be obtained from a call to get_nmfields_by_type(3).

The caller may not modify any strings in the array, or the array itself. Doing so may cause database corruption. The pointer returned is guaranteed to be valid until get_mfield_list_by_type() is called again with the same arguments, or until the array is deallocated by a call to dirfile_close(3).

For CONST and STRING field types, corresponding lists of values for may be obtained by calling get_mconstants(3) or get_mstrings(3).


Upon successful completion, get_mfield_list_by_type() returns a pointer to an array of strings containing the names of all the metafields of the specific type for the given parent. On error it returns NULL and sets the dirfile error to a non-zero error value. Possible error values are:
The library was unable to allocate memory.
The supplied parent field code was not found, or referred to a metafield itself.
The supplied dirfile was invalid. The dirfile error may be retrieved by calling get_error(3). A descriptive error string for the last error encountered can be obtained from a call to get_error_string(3).