Microsoft KB Archive/32736

PRB: Determining a File’s Name Given a File Handle ID Number: Q32736

2.x 3.x 4.00 4.00a 4.01 4.01a 5.00 MS-DOS

Summary:

SYMPTOMS Given a file handle number for an open file handle, there is no way to get the file specification (the filename) of this open file handle.

CAUSE Normally, this information is not needed, since there are usually two situations in which an application has a file handle. The most common one is that it has opened the file itself; in this case, the application should have the filename already and should not forget it. If it inherited this file from a parent process, it should not need to know what the filename is, since the application is in the process of redirection, and should “trust” its parent process in its choice of input and output files.

RESOLUTION One workaround for this problem is to have an interrupt service routine (ISR) trap the MS-DOS system service for opening a file (interrupt 21h service 3Dh) and store the filename information, along with the PSP (process ID) of the process that opened it. Then, this ISR could in turn allocate one of the user-definable interrupts (60h through 67h). Given a process ID and a handle number, it could conceivably return the actual filename. However, this would be difficult to write, since it would be very hard for the ISR to determine which process owned the file.

Additional reference words: 2.x 3.x 4.00 4.00a 4.01 4.01a 5.00