Kage has asked for the wisdom of the Perl Monks concerning the following question:

ok... if I did like 
open (FILE,"<$footer");
if ($lock){ flock(DATA, $lock)}
@footerfile = <FILE>;
close(FILE);
foreach $footerline(@footerfile) {
print "$footerline";
}

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how would I put in a  while( $tmpl = <FILE> ) { $tmpl =~ s/<<whatever>>/$whatever/g; } ?

Edit kudra, 2001-10-30 Changed title

Replies are listed 'Best First'.
Re: Oooh, Oooh, Help Me Help Me (:
by jj808 (Hermit) on Oct 28, 2001 at 07:44 UTC
    Use grep map. Update: Of course, ChemBoy is entirely right about this. That's what I get for posting after a 13-hour night shift...

    If you just want to print the (modified) contents of the file, you can do 

    open (FILE,"<$filename") or die "Cannot open: $!";
map{s/stuff/other_stuff/g;print}(<FILE>);

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    Or if you want to keep the modified file in an array, try 
    open (FILE,"<$filename") or die "Cannot open: $!";
@ary = map{s/stuff/other_stuff/g}(<FILE>);

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    Update: You could also do this as a one-liner: 
    perl -pe 's/stuff/other_stuff/g' filename.txt

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    Hope this helps,

    JJ

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      No, please don't use grep that way, unless you actually want to strip lines out of your input if they don't match the substitution pattern. Use map, instead--that's what it's for. 

      @footerfile = map {s/something/else/} <FILE>;

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      Note that the first solution proposed using grep wouldn't have the undesired side-effects, but it's still bad coding practice--never use grep or map in void context (obfuscatory and inefficient).

      And Kage, please find a better descriptive title for your question next time...

      Update: or, of course, you could alter the array in place after reading it in, using 

      s/nothing/something/ for @footerfile;

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      Update 2: of course, it would help if I told you the right syntax for map, too... 

      @footerfile = map {s/something/else/;$_} <FILE>;

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      (thanks, Zaxo! And I wish I had as good an excuse as jj808 for screwing this one up....)


      If God had meant us to fly, he would *never* have given us the railroads.
          --Michael Flanders

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Re: How can I make a regex apply to each line of a file?
by Hofmator (Curate) on Oct 30, 2001 at 21:02 UTC

    and it might be a good idea to check the return value of your open call open (FILE, "<$footer") or die "Couldn't open file $footer: $!";

    Apart from that, it might not be necessary to read the whole file into memory. So you could do something like 

    open (FILE, "<$footer") or die "Couldn't open file $footer: $!";

while (my $line = <FILE>) {
  $line =~ s/something/something_else/g;
  
  # print changed line
  print $line;

  # do some very complicated other stuff here
}
close FILE;

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    But this depends strongly on what you are doing with the lines of the file.

    Update: Added comment pointing to more complex operations in while loop.

    Thanks davorg, I was aware of your command line solution. Nevertheless I posted in order to stress the fact that there is the while-loop alternative to the memory intensive 'map on array' which was suggested by jj808 and ChemBoy. And I assumed that Kage wanted to do a little bit more than just printing the changed line - although my short snippet didn't show that :)

    -- Hofmator

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      That's the kind of thing that Perl command line options make very easy:

      perl -i.bak -pe 's/something/something else/g' input.txt

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      --
      <http://www.dave.org.uk>

      "The first rule of Perl club is you don't talk about Perl club."

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