How to make a script for two txt files with different names in perl - perl

Question

I want to make the same calculations in two similar files, but I do not want to double the code for each file nor to create two scripts for this.
my $file = "file1.txt";
my $tempfile = "file1_temp.txt";
if (not defined $file) {
die "Input file not found";
}
open(my $inputFileHandler, '<:encoding(UTF-8)', $file)
or die "Could not open file '$file' $!";
open(my $outs, '>', $tempfile) or die $!;
/*Calculations made*/
close($outs);
copy($tempfile,$file) or die "Copy failed: $!";
unlink($tempfile) or die "Could not delete the file!\n";
close($inputFileHandler);
So i want to do the exact calculations for file2.txt_temp and copy it in file2.txt is there a way to do it without writing the code again for file2?
Thank you very much.

Answer 1

Write your code as a Unix filter. Read the data from STDIN and write it to STDOUT. Your code will be simpler and your program will be more flexible.
#!/usr/bin/perl
use strict;
use warnings;
while (<STDIN>) {
# do a calculation using the data that is in $_
print $output_data
}
The cleverness is in how you call the program:
$ ./my_clever_filter < file1.txt > file1_out.txt
$ ./my_clever_filter < file2.txt > file2_out.txt
See The Unix Filter Model: What, Why and How? for far more information.

Answer 2

Assuming your code is well written (not manipulating any globals, ...) you could use a for-loop
foreach my $prefix ('file1', 'file2') {
my $file = $prefix . ".txt";
my $tempfile = $prefix . "_temp.txt";
...
}

Answer 3

There is a certain Perl feature that is designed especially for cases like this, and that is this:
$ perl -pi -e'/*Calculations made*/' file1.txt file2.txt ... fileN.txt
Loosely referred to as "in-place edit", which basically does what your code does: It writes to a temp file and then overwrites the original.
Which will apply your calculations to the files named as arguments. If you have complex calculations you can put them in a file and skip the -e'....' part
$ perl -pi foo.pl file1.txt ...
Say for example that your "calculations" consist of incrementing each pair of numbers by 1:
s/(\d+) (\d+)/($1 + 1) . ($2 + 1)/ge
You would do either
$ perl -pi -e's/(\d+) (\d+)/($1 + 1) . ($2 + 1)/ge' file1.txt file2.txt
$ perl -pi foo.pl file1.txt file2.txt
Where foo.pl contains the code.
Be aware that the -i switch is destructive, so make backups before running the command. You can supply a backup extension to save a backup, but that backup is overwritten if you run the command again. E.g. -i.bak.
-p places a while (<>) loop around your code, followed by a print of each line,
-i.bak does the editing of the original file, and saves a backup with the extension, if it is supplied.