File: gawk.info,  Node: Special Caveats,  Prev: Special Network,  Up: Special Files

5.8.3 Special File name Caveats
-------------------------------

Here are some things to bear in mind when using the special file names
that 'gawk' provides:

   * Recognition of the file names for the three standard preopened
     files is disabled only in POSIX mode.

   * Recognition of the other special file names is disabled if 'gawk'
     is in compatibility mode (either '--traditional' or '--posix';
     *note Options::).

   * 'gawk' _always_ 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.