Regular Expressions

grep and replace

[Reynolds]

Hello
This may be the wrong forum but I know a lot of you are very sharp so I'm going to try.
I have a bunch of .txt files. Each file has a common string of text.

Does anyone have or know of a script that will parse the files, grep the string and replace it with another?

Thank you very much.
Eric Reynolds

[oilman]

Welcome to the forums Reynolds. Sorry I can't answer your question but I know a number of folks around here can do that stuff in their sleep. ;)

Guys...little help?

[littleman]

At the simplest level you would do something like this:

#!/usr/bin/perl
$fine = "what_you_want_put";
$replace = "what_to_put_in";
  open(FILE,"/path/to/file");
 my(@lines) = <FILE>;
 close(FILE);
foreach $words (@lines) {
  $words =~ s/$fine/$replace/g;
}

So what do you want to do with it then? Print it, or replace the file with the altered one?

[DaveAtIFG]

A handy-dandy quick reference on regular expressions is at [brainstorm.co.uk...]
It may help with LM's variables "what_you_want_put" and "what_to_put_in".
[marker rcjordan]

Edited by: rcjordan

[littleman]

Dave, nice link - it is kind of like a handy reference sheet.

[Reynolds]

Thank you very much everyone.

[Brett_Tabke]

And keeping with the net geek perl creed of nitpicking any perl post (lm understands) here is a version that will work with larger files. Takes the input file and outputs it to the output file.

#!/usr/bin/perl
$fine = "source string";
$replace = "replacement string";
open(FILE2,"> /path/to/outputfile");
open(FILE,"< /path/to/inputfile");
while (<FILE>) {
 chomp;  #incase moving across file systems linux<->win
 s/$fine/$replace/gi;
 print FILE2 "$_\n";
}
 close(FILE);
 close(FILE2); #file is now in file2

btw: this post will eventually move to the technology forum. I love code discussions and hope we can generate enough interest to justify a cgi/perl forum in the near future.

[littleman]

Ok, here is more for you to nitpick. I wasn't sure which way we were going to go with this, but it looks now like we are talking about getting a file and altering it - as
oppose to printing it. So I threw this together:

#!/usr/bin/perl
#the path to the files
$serverpath = "/path/to/files/";
#the docs you want changed
$doctype = "txt";
#the string to look for
$fine = "source string";
#what you want to replace it with
$replace = "replacement string";
#
#
#ok, getting started
print "Finding \"$fine\" and replacing it with \"$replace\"\n";
#going to directory
opendir(DIR, "$serverpath");
#looking for files
@files = grep(/\.$doctype$/,readdir(DIR));
closedir(DIR);
#lining the files up
foreach $file(@files){
#opening the file to read it
 print "opening file $serverpath$file\n";
 open(FILE,"$serverpath/$file");
 my(@subm) = <FILE>;
 close(FILE);
#clear the document
 open(CLR,">$serverpath/$file");
 close(CLR);
 $n=0;
#printing new
 foreach $line (@subm) {
 $line =~ s/$fine/$replace/g;
 open(SUB,">>$serverpath/$file");
 print SUB $line;
 close(SUB);
 $n++;
 }
 print "$n lines searched in $file\n";
}

It will search and replace an entire folder for an extension and then will do a search and replace for all the docs.

[NFFC]

Hmmm...

#!/usr/bin/perl
#the path to the files
$serverpath = "/help/needed/here/";
#the docs you want changed
$doctype = "genuine";
#the string to look for
$fine = "learn perl";
#what you want to replace it with
$replace = "no rush";
#
#
#ok, getting started
print "Finding \"$fine\" and replacing it with \"$got books\"\n";
#going to directory
opendir(DIR, "$serverpath"[just need]);
#looking for files
@files = grep(/\.$doctype$/,readdir(DIR));
closedir(DIR);
#lining the files up
foreach $file(@files){
#opening the file to read it
 print "opening file $serverpath$file\n";
 open(FILE,"$serverpath/$file"[a bit]);
 my(@subm) = <FILE>;
 close(FILE);
#clear the document
 open(CLR,">$serverpath/$file"[of backup]);
 close(CLR);
 $n=0;
#printing new
 foreach $line (@subm) {
 $line =~ s/$fine/$replace/g;
 open(SUB,">>$serverpath/$file"[any takers]);
 print SUB $line;
 close(SUB);
 $n++;
 }
 print "$n lines searched in $file\n";
}

This might be worth considering. ;)

[littleman]

Ok

#!/usr/bin/perl
#the path to the files
$serverpath = "/path/to/files";#no trailing slash
#the docs you want changed
$doctype = "txt";
#the string to look for
$fine = "source string";
#what you want to replace it with
$replace = "replacement string";
#
#
#ok, getting started
print "Finding \"$fine\" and replacing it with \"$replace\"\n";
#going to directory
opendir(DIR, "$serverpath");
#looking for files
@files = grep(/\.$doctype$/,readdir(DIR));
closedir(DIR);
#lining the files up
foreach $file(@files){
$pa_fi = "$serverpath/$file";
#opening the file to read it
 print "opening file $pa_fi\n";
 open(FILE,"$pa_fi");
 my(@subm) = <FILE>;
 close(FILE);
#backup the document
  rename $pa_fi, $pa_fi . '.bac';
print "making backup\n";
 $n=0;
#printing new
 foreach $line (@subm) {
  $line =~ s/$fine/$replace/g;
  open(SUB,">>$pa_fi");
  print SUB $line;
  close(SUB);
  $n++;
 }
 print "$n lines searched in $file\n";
}

[Brett_Tabke]

Ok, lets go the other way this time instead of nitpicking, lets point out some of the better lines. The best snip of the whole thread is this one:

opendir(DIR, "$serverpath");
@files = grep(/\.$doctype$/,readdir(DIR));
closedir(DIR);

There are alot of people who try to hand parse out files through complicated reg ex includes/excludes. The above is sweet, simple, and fast. It could use a dose of pre-error checking to double check that the dir exists, but we'll leave that as an exercise for the reader.

[sugarkane]

A quick and dirty version if you have access to perl from the shell:

perl -e 's/old string/new string/' -p -i.bak *.txt

[littleman]

sugarkane
Nice one-liner! Anyone know of a website that specializes in command line tricks?