gawk: Special Caveats

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1 5.8.3 Special File name Caveats
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1 Here are some things to bear in mind when using the special file names
1 that 'gawk' provides:
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1    * Recognition of the file names for the three standard preopened
1      files is disabled only in POSIX mode.
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1    * Recognition of the other special file names is disabled if 'gawk'
1      is in compatibility mode (either '--traditional' or '--posix';
1      ⇒Options).
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1    * 'gawk' _always_ interprets these special file names.  For example,
1      using '/dev/fd/4' for output actually writes on file descriptor 4,
1      and not on a new file descriptor that is 'dup()'ed from file
1      descriptor 4.  Most of the time this does not matter; however, it
1      is important to _not_ close any of the files related to file
1      descriptors 0, 1, and 2.  Doing so results in unpredictable
1      behavior.
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