fd(4)                                                          fd(4)


       NAME
             fd - file descriptor files

       SYNOPSIS
             /dev/fd/*

       DESCRIPTION
             These files, conventionally called /dev/fd/0, /dev/fd/1,
             /dev/fd/2, and so on, refer to files accessible through file
             descriptors.  If file descriptor n is open, these two system
             calls have the same effect:
                   fd = open("/dev/fd/n",mode);
                   fd = dup(n);

             On these files creat(2) is equivalent to open, and the read
             and write bits are ignored and O_TRUNC is failed with ENOSYS.
             As with dup, subsequent reads or writes on fd fail unless the
             original file descriptor allows the operations.

             For convenience in referring to standard input, standard
             output, and standard error, an additional set of names is
             provided: /dev/stdin is a synonym for /dev/fd/0, /dev/stdout
             for /dev/fd/1, and /dev/stderr for /dev/fd/2.

       REFERENCES
             access(2), dup(2), ls(1) open(2), stat(2)

       NOTICES
             open(2) returns -1 and EBADF if the associated file descriptor
             is not open.  However, if the truncation is specified in the
             call to open, then ENOSYS is returned.  If a file is open for
             reading, an attempt to reopen it for writing will fail;
             instead a new file descriptor (read-only) is created.

             access(2) always returns with success.  stat(2) returns a
             reasonable value for /dev/fd itself, but when called for files
             in /dev/fd, the attributes for those ``files'' are faked.
             Note also that using ls(1) on /dev/fd always lists nf files,
             where nf is the user's current soft limit for open files, and
             not only those the user has opened.








                           Copyright 1994 Novell, Inc.               Page 1