This example sends a message to the output file "MYMSG.DAT", automatically wrapping if necessary.

#define INCL_DOSFILEMGR /* File Manager values */
#define INCL_DOSMISC    /* Miscellaneous values */
#define INCL_DOSERRORS  /* DOS Error values */
#include <os2.h>
#include <stdio.h>
#include <string.h>

int main(VOID) {

HFILE   FileHandle       = NULLHANDLE;      /* File handle */
ULONG   ulAction         = 0;               /* Action taken by DosOpen */
UCHAR   uchDataArea[160] = "";              /* Message buffer */
APIRET  rc               = 0;               /* Return code */

rc = DosOpen ("MYMSG.DAT", &FileHandle, &ulAction, 120L, FILE_ARCHIVED,
              OPEN_ACTION_CREATE_IF_NEW | OPEN_ACTION_OPEN_IF_EXISTS,
              OPEN_FLAGS_NOINHERIT | OPEN_SHARE_DENYREADWRITE |
              OPEN_ACCESS_READWRITE, 0L);

strcpy (uchDataArea, "This is a sample message that is going to be written ");
strcat (uchDataArea, "to the message file.  It is longer than 80");
strcat (uchDataArea, " characters, so it should wrap.              ");

rc = DosPutMessage(FileHandle, strlen(uchDataArea), uchDataArea);
if (rc != NO_ERROR) {
   printf("DosPutMessage error: return code = %u\n", rc);
   return 1;
}

rc = DosClose(FileHandle);

return NO_ERROR;
}