Perl replacing Strings from files in directory

Question

I'm trying to make a program that replaces a string in all files in a directory. The catch is that I need to make it possible to only change it if it is at the beginning of a sentence or at the end, or both. This is what I have so far:

use strict;
use warnings;
use File::Find;     #This lets us use the find() function, similar to 'find' in Unix 
                # -- which is especially helpful for searching recursively.

print "Which directory do you want to use?\n"; #Ask what directory to use
my $dir = readline STDIN;
chomp $dir; #Used for eliminating the newline character '\n'

print "What String would you like to search for?\n"; #Ask for what String to search for.
my $search = readline STDIN;
chomp $search;

print "What String would you like to replace it with?\n"; #Ask for what to replace it with.
my $replace = readline STDIN;
chomp $replace;

print "Would you like to replace $search if it is at the beginning of the sentence? (y/n) \n";
my $beg = readline STDIN;
chomp $beg;

print "Would you like to replace $search if it is at the end of the sentence? (y/n) \n";
my $end = readline STDIN;
chomp $end;


find(\&txtrep, $dir); #This function lets us loop through each file in the directory

sub txtrep  {
    if ( -f and /.txt$/) { # Proceeds only if it is a regular .txt file
        my $file = $_;  # Set the name of the file, using special Perl variable
        open (FILE , $file);
        my @lines = <FILE>; #Puts the file into an array and separates sentences
        my @lines2 = split(".", @lines);
        close FILE;

        if ($beg eq "y") {
            foreach my $slot (@lines2) {
                $slot =~ s/^$search/$replace/gi;
            }
        }

        if ($end eq "y") {
            foreach my $slot (@lines2) {
                $slot =~ s/$search$/$replace/gi;
            }
        }

        open (FILE, ">$file");
        print FILE @lines2;
        close FILE;
    }
}

After I run this, it just deletes everything in the files, and I don't know if the syntax is right for changing the string @ the beginning and the end of the sentences. Please let me know what I am doing wrong! Thank you!

Answer 1

I would just use a perl one-liner

perl -i.bak -pe 's/^[search]/[replace]/g;' [files] for a beginning of a line perl -i.bak -pe 's/[search]$/[replace]/g;' [files] for the end of the line

[search] and [replace] are place holders.

the '-i.bak' will make a backup of the file prior to replacement.

quick google search: perl one-liner search & repalce example

Answer 2

You have use strict; on, but you have a syntax error with using the variable @lines2 .

Also, you should add use autodie; , since you're doing file processing.

The following is probably what you're searching for:

my $data = do {
    open my $fh, $file;
    local $/;
    <$fh>
};

if ($beg eq "y") {
    $data =~ s/(?:^|(?<=\.))\Q$search\E/$replace/gim;
}

if ($end eq "y") {
    $data =~ s/\Q$search\E(?=\.|$)/$replace/gim;
}

open my $fh, '>', $file;
print $fh $data;
close $fh;

Obviously, your code could probably be tightened up more, but the above should get it working.