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From: lwall@jato.Jpl.Nasa.Gov (Larry Wall)
Newsgroups: comp.unix.questions,gnu.misc.discuss,comp.lang.perl
Subject: Re: Passing variables to gawk
Message-ID: <2609@jato.Jpl.Nasa.Gov>
Date: 19 Jan 90 02:47:07 GMT
References: <MIKEMC.90Jan17141246@mustang.ncr-fc.FtCollins.NCR.com>
Reply-To: lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall)
Distribution: comp, gnu
Organization: Jet Propulsion Laboratory, Pasadena, CA
Lines: 34

In article <MIKEMC.90Jan17141246@mustang.ncr-fc.FtCollins.NCR.com> mikemc@mustang.ncr-fc.FtCollins.NCR.com (Mike McManus) writes:
: 
: I want to pass variables to a gawk program via the command line.  According to
: the man page, all you need do is call gawk with <var>=<value> instead of file
: names:
: 
: gawk -f foo.awk a=1 b=2 c=3 infile > outfile
: 
: and the variables a,b,c will be free to use in foo.awk (the gawk script), and
: will be assigned the values 1,2,3.  I can't seem to get this to work!  When I
: print the value of the variables inside a BEGIN{} block in foo.awk, they are
: all set to 0.  Anybody have any experience with this that they'd like to
: share?

I believe this is called "bug emulation".  awk itself has the same problem.

(It is possible that this was not considered a bug when first implemented.
I can imagine someone wishing to override the BEGIN section from the command
line.  Let us be charitable, and call it a misleading feature  :-)

I chose not to emulate this particular misleading feature in the awk-to-perl
translator.  The produced perl script evaluates the foo=bar switches before
doing the "BEGIN" stuff.  If you want the other behavior, you can just move
the line that does that, which says

    eval '$'.$1.'$2;' while $ARGV[0] =~ /^([A-Za-z_]+=)(.*)/ && shift;

down below the stuff derived from BEGIN.

Oddly enough, in the version of nawk I have access to, it is documented
to have the buggy behavior, but, in fact, works right.  Go figure.

Larry Wall
lwall@jpl-devvax.jpl.nasa.gov