This function will determine (if possible) the format of a file by either using the file name or querying currently installed I/O procedures to see which I/O procedure can understand and process the specified file.

#define INCL_MMIOOS2
#include <os2.h>

PSZ              pszFileName;        /*  Filename. */
PMMIOINFO        pmmioinfo;          /*  Pointer to MMIOINFO. */
PMMFORMATINFO    pmmformatinfo;      /*  Pointer to MMFORMATINFO. */
PFOURCC          pfccStorageSystem;  /*  FOURCC pointer. */
ULONG            ulReserved;         /*  Reserved. */
ULONG            ulFlags;            /*  Flags. */
ULONG            rc;                 /*  Return codes. */

rc = mmioIdentifyFile(pszFileName, pmmioinfo,
       pmmformatinfo, pfccStorageSystem, ulReserved,
       ulFlags);