Here are some things to bear in mind when using the
special file names that
gawkis in compatibility mode (either --traditional or --posix; see Command-Line Options).
gawkalways interprets these special file names. For example, using ‘/dev/fd/4’ for output actually writes on file descriptor 4, and not on a new file descriptor that is
dup()ed from file descriptor 4. Most of the time this does not matter; however, it is important to not close any of the files related to file descriptors 0, 1, and 2. Doing so results in unpredictable behavior.