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Using `gawk' on PC Operating Systems
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   The OS/2 and MS-DOS versions of `gawk' search for program files as
described in Note: The `AWKPATH' Environment Variable.
However, semicolons (rather than colons) separate elements in the
`AWKPATH' variable. If `AWKPATH' is not set or is empty, then the
default search path is `".;c:/lib/awk;c:/gnu/lib/awk"'.

   An `sh'-like shell (as opposed to `command.com' under MS-DOS or
`cmd.exe' under OS/2) may be useful for `awk' programming.  Ian
Stewartson has written an excellent shell for MS-DOS and OS/2, Daisuke
Aoyama has ported GNU `bash' to MS-DOS using the DJGPP tools, and
several shells are available for OS/2, including `ksh'.  The file
`README_d/README.pc' in the `gawk' distribution contains information on
these shells.  Users of Stewartson's shell on DOS should examine its
documentation for handling command lines; in particular, the setting
for `gawk' in the shell configuration may need to be changed and the
`ignoretype' option may also be of interest.

   Under OS/2 and DOS, `gawk' (and many other text programs) silently
translate end-of-line `"\r\n"' to `"\n"' on input and `"\n"' to
`"\r\n"' on output.  A special `BINMODE' variable allows control over
these translations and is interpreted as follows.

   * If `BINMODE' is `"r"', or `(BINMODE & 1)' is nonzero, then binary
     mode is set on read (i.e., no translations on reads).

   * If `BINMODE' is `"w"', or `(BINMODE & 2)' is nonzero, then binary
     mode is set on write (i.e., no translations on writes).

   * If `BINMODE' is `"rw"' or `"wr"', binary mode is set for both read
     and write (same as `(BINMODE & 3)').

   * `BINMODE=NON-NULL-STRING' is the same as `BINMODE=3' (i.e., no
     translations on reads or writes).  However, `gawk' issues a warning
     message if the string is not one of `"rw"' or `"wr"'.

The modes for standard input and standard output are set one time only
(after the command line is read, but before processing any of the `awk'
program).  Setting `BINMODE' for standard input or standard output is
accomplished by using an appropriate `-v BINMODE=N' option on the
command line.  `BINMODE' is set at the time a file or pipe is opened
and cannot be changed mid-stream.

   The name `BINMODE' was chosen to match `mawk' (Note: Other Freely
Available `awk' Implementations.).  Both `mawk' and
`gawk' handle `BINMODE' similarly; however, `mawk' adds a `-W
BINMODE=N' option and an environment variable that can set `BINMODE',
`RS', and `ORS'.  The files `binmode[1-3].awk' (under `gnu/lib/awk' in
some of the prepared distributions) have been chosen to match `mawk''s
`-W BINMODE=N' option.  These can be changed or discarded; in
particular, the setting of `RS' giving the fewest "surprises" is open
to debate.  `mawk' uses `RS = "\r\n"' if binary mode is set on read,
which is appropriate for files with the DOS-style end-of-line.

   To Illustrate, the following examples set binary mode on writes for
standard output and other files, and set `ORS' as the "usual" DOS-style
end-of-line:

     gawk -v BINMODE=2 -v ORS="\r\n" ...

or:

     gawk -v BINMODE=w -f binmode2.awk ...

These give the same result as the `-W BINMODE=2' option in `mawk'.  The
following changes the record separator to `"\r\n"' and sets binary mode
on reads, but does not affect the mode on standard input:

     gawk -v RS="\r\n" --source "BEGIN { BINMODE = 1 }" ...

or:

     gawk -f binmode1.awk ...

With proper quoting, in the first example the setting of `RS' can be
moved into the `BEGIN' rule.