NAME dup - duplicate an open file descriptor SYNOPSIS (dup = 41.; not in assembler) (file descriptor in r0) sys dup dup(fildes) int fildes; DESCRIPTION Given a file descriptor returned from an open, pipe, or creat call, dup will allocate another file descriptor syn- onymous with the original. The new file descriptor is returned in r0. Dup is used more to reassign the value of file descriptors than to genuinely duplicate a file descriptor. Since the algorithm to allocate file descriptors returns the lowest available value, combinations of dup and close can be used to manipulate file descriptors in a general way. This is handy for manipulating standard input and/or standard out- put. SEE ALSO creat (II), open (II), close (II), pipe (II) DIAGNOSTICS The error bit (c-bit) is set if: the given file descriptor is invalid; there are already too many open files. From C, a -1 returned value indicates an error. 1