FcConfigFilename − Find a config file

#include <fontconfig.h>

char * FcConfigFilename (const char *name);

     Given the specified external entity name, return the
associated filename.  This provides applications a way to
convert various configuration file references into filename

     A null or empty name indicates that the default
configuration file should be used; which file this
references can be overridden with the FC_CONFIG_FILE
environment variable.  Next, if the name starts with ~, it
refers to a file in the current users home directory.
Otherwise if the name doesn’t start with ’/’, it refers to a
file in the default configuration directory; the built‐in
default directory can be overridden with the FC_CONFIG_DIR
environment variable.

     Fontconfig version 2.4.2