From: Josef 'Jupp' SCHUGT <jupp@...>
Date: 2004-03-12T05:58:37+09:00
Subject: Re: Novice question, tranlate awk code to ruby code

Hi!

* Horacio Castellini:

> I'm a novice ruby user, but ancient user in Linux world. We assume
> have a data file with two data field in two columns. In awk program
> when I like time them a script code may be:
> 
> {
>     print $1*$2
> }
> 
> for example I can use "% cat foo.dat|awk -f times.awk" d'accorde.
> Well, how can I do this in ruby code?

First some remark on the above command line: It is unnecessarily 
complicated, 

    awk '{print $1 * $2}' times.awk

works as well. Two solutions using Ruby. First one does integer 
arithmetics:

    ruby -a -n -e 'puts $F[0].to_i * $F[1].to_i'

Second one does floating-point arithmetics:

    ruby -a -n -e 'puts $F[0].to_f * $F[1].to_f'

They only differ in the type conversion part.

'-e' means that what follows is code to be executed.

'-n' makes the Ruby iterate over all lines successively assigning
     them to $_

'-a' makes Ruby split $_ into its parts assigning the result to $F 
     which is an array of strings

To specify the column separator you can use the '-F' option that is 
familiar from awk.

Please note that awk's $0 maps to Ruby's $_ and that $1, $2, ... map 
to $F[0], $F[1], ...

HTH,

Josef 'Jupp' SCHUGT
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