Microsoft KB Archive/32800

INF: How to Truncate a File ID Number: Q32800

2.x 3.x 4.x 5.00 MS-DOS

Summary:

The following is a fast algorithm for truncating a file handle using the MS-DOS file handle services of interrupt 21h:


 * 1) Open the file using interrupt 21h service 03Dh (open file handle).
 * 2) Move the file pointer to the point at which truncation is to occur using interrupt 21h service 042h (move file handle pointer).
 * 3) Write 0 bytes to the file using interrupt 21h service 040h (write file handle).
 * 4) Close the file using interrupt 21h service 03Eh (close file handle).