5.7.4 Special File Name Caveats

Here is a list of things to bear in mind when using the special file names that gawk provides.

• Recognition of these special file names is disabled if gawk is in compatibility mode (see section Command-Line Options).

• The As mentioned earlier, the special files that provide process-related information are now considered obsolete and will disappear entirely in the next release of gawk. gawk prints a warning message every time you use one of these files. To obtain process-related information, use the PROCINFO array. See section 7.5 Built-in Variables.

• Starting with version 3.1, gawk always interprets these special file names.(18) 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.