This example opens, or creates and opens, a file named "DOSTEST.DAT", writes to it, reads from it, and finally closes it.
#define INCL_DOSFILEMGR /* File Manager values */ #define INCL_DOSERRORS /* DOS Error values */ #include <os2.h> #include <stdio.h> #include <string.h> int main(void) { HFILE hfFileHandle = 0L; /* Handle for file being manipulated */ ULONG ulAction = 0; /* Action taken by DosOpen */ ULONG ulBytesRead = 0; /* Number of bytes read by DosRead */ ULONG ulWrote = 0; /* Number of bytes written by DosWrite */ ULONG ulLocal = 0; /* File pointer position after DosSetFilePtr */ UCHAR uchFileName[20] = "dostest.dat", /* Name of file */ uchFileData[100] = " "; /* Data to write to file */ APIRET rc = NO_ERROR; /* Return code */ /* Open the file dostest.dat. Use an existing file or create a new */ /* one if it doesn't exist. */ rc = DosOpen(uchFileName, /* File path name */ &hfFileHandle, /* File handle */ &ulAction, /* Action taken */ 100L, /* File primary allocation */ FILE_ARCHIVED | FILE_NORMAL, /* File attribute */ OPEN_ACTION_CREATE_IF_NEW | OPEN_ACTION_OPEN_IF_EXISTS, /* Open function type */ OPEN_FLAGS_NOINHERIT | OPEN_SHARE_DENYNONE | OPEN_ACCESS_READWRITE, /* Open mode of the file */ 0L); /* No extended attribute */ if (rc != NO_ERROR) { printf("DosOpen error: return code = %u\n", rc); return 1; } else { printf ("DosOpen: Action taken = %ld\n", ulAction); } /* endif */ /* Write a string to the file */ strcpy (uchFileData, "testing...\n1...\n2...\n3\n"); rc = DosWrite (hfFileHandle, /* File handle */ (PVOID) uchFileData, /* String to be written */ sizeof (uchFileData), /* Size of string to be written */ &ulWrote); /* Bytes actually written */ if (rc != NO_ERROR) { printf("DosWrite error: return code = %u\n", rc); return 1; } else { printf ("DosWrite: Bytes written = %u\n", ulWrote); } /* endif */ /* Move the file pointer back to the beginning of the file */ rc = DosSetFilePtr (hfFileHandle, /* File Handle */ 0L, /* Offset */ FILE_BEGIN, /* Move from BOF */ &ulLocal); /* New location address */ if (rc != NO_ERROR) { printf("DosSetFilePtr error: return code = %u\n", rc); return 1; } /* Read the first 100 bytes of the file */ rc = DosRead (hfFileHandle, /* File Handle */ uchFileData, /* String to be read */ 100L, /* Length of string to be read */ &ulBytesRead); /* Bytes actually read */ if (rc != NO_ERROR) { printf("DosRead error: return code = %u\n", rc); return 1; } else { printf ("DosRead: Bytes read = %u\n%s\n", ulBytesRead, uchFileData); } /* endif */ rc = DosClose(hfFileHandle); /* Close the file */ if (rc != NO_ERROR) { printf("DosClose error: return code = %u\n", rc); return 1; } return NO_ERROR; }