This function sets attributes of the media in a file opened for writing by mmioOpen. It issues an MMIOM_SETHEADER message to the I/O procedure. The specific header depends on the media type of the file and current track setting, in the case of multiple tracks. This header can be a raw header or a translated header.

This function does not change the current file position. Typically, mmioGetHeader is issued to obtain the attribute data and mmioSetHeader is issued to update it. mmioSetHeader can be issued independently of mmioGetHeader, such as to create the header initially.

#define INCL_MMIOOS2
#include <os2.h>

HMMIO    hmmio;           /*  Open file handle. */
PVOID    pHeader;         /*  Pointer to header structure. */
LONG     lHeaderLength;   /*  Size of header structure. */
PLONG    plBytesWritten;  /*  # of bytes written. */
ULONG    ulReserved;      /*  Reserved. */
ULONG    ulFlags;         /*  Reserved. */
ULONG    rc;              /*  Return codes. */

rc = mmioSetHeader(hmmio, pHeader, lHeaderLength,
       plBytesWritten, ulReserved, ulFlags);