Disambiguating file descriptors

Abstract

File descriptors associated with specific file types are disambiguated from other file descriptors by maintaining and examining an indicator table containing indicators concerning file descriptors associated with a specific, desired file type. System calls that establish a descriptor of the specific, desired type are intercepted, and an indicator concerning the established file descriptor is added to the indicator table. To keep the indicator table current, system calls that make a copy of a file descriptor or that delete a file descriptor are intercepted. If a file descriptor associated with the desired type is copied or deleted, the indicator table is updated. Therefore, the indicator table preferably includes indicators concerning all file descriptors associated with files of the specific desired type. The indicator table is examined to determine whether or not a specific file descriptor is of the desired type. In one embodiment, system calls that access files via file descriptors are intercepted, and the system call wrapper examines the indicator table to determine whether the file being accessed is of the desired type. Only if the file is of the desired type does the system call wrapper continues to execute. If the file is not of the desired type, the default system call is made. Thus, system calls that access files are selectively intercepted based upon file type.