From: Peter Bailey <pbailey@...>
Date: 2006-04-12T20:58:17+09:00
Subject: Simple substitutions

Hello,
Some of you all helped this newbie a couple of weeks ago. I'm getting 
there!

I have a need to parse postscript print files on a daily basis. Some of 
them are over 10 mB. One thing I need to find out is the number of pages 
in the files. There's a simple one-liner at the top of each .ps file 
that states the number of pages. It reads:
                             %%Pages: xx
It's a line of its own.

I simply want to find that line in my source file and then write a 
corresponding line in my output file:
                             Number of pages: xx

I tried the following in IRB, but I get the syntax error shown below.

     File.open("psout.txt", "w") do |output|
       File.foreach("test1.ps") do |line|
         line.sub!(/\%\%Pages: ([0-9]{1,5})/"Pages: \1"/)
         output << line
       end
     end

    SyntaxError: compile error
    (irb):26: parse error, unexpected tSTRING_BEG, expecting ')'
    line.sub!(/\%\%Pages: ([0-9]{1,5})/"Pages: \1"/)
                                    ^
    (irb):26: parse error, unexpected ')'
           from (irb):29

Is there a significance to the ^ under the "P" in my syntax error? 
What's it telling me? My sub requires parentheses. Is there a conflict 
with my grouping parentheses inside my regular expression?

Another request for help--my translation above would basically move the 
entire contents of my source file to the target file, with the exception 
of the one line I want changed. That's overkill for me. I just want a 
few lines of information in my target file. Would you suggest I just do 
a simple search, using matching (=~), and then write about that find in 
my target file, or, would it be better to do mass deletions of 
everything I don't want from my source to my target files? In other 
words, should I say "in this file, find this, then say this . . ." or, 
"convert this entire file, but just change this?"

Thank you.


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