6/17/2023 Intro to Perl

Install on MacOs

Install perl with brew install perl

$ command -v perl

/opt/homebrew/bin/perl

Let's print file.txt with perl :

perl -p -e '' file.txt

The -p option implicitly runs a loop that prints the content of _$ each time around the loop.

LINE:
  while (<>) {
    # your code goes here
  } continue {
    print or die "-p destination: $!\n";
  }

This above uses the (little-used) continue block on a while loop to ensure that the print statement is always called.

So let's give an example using this option : print the number of the line before each line

perl -p -e '$_ = "$. - $_"' file.txt

Let's use a search and replace regex to edit a file :

perl -pe 's/\bPHP\b/Perl/g' < file.txt > edited_file.txt

Same, but overwriting file.txt :

perl -i -pe 's/\bPHP\b/Perl/g' file.txt

Same, but with a backup in file.txt.bak :

perl -i.bak -pe 's/\bPHP\b/Perl/g' file.txt

vim can be tremendously slow when running a command like :

:%s/\n//g

To achieve the same, inside vim with perl :

First go to the top of the file with gg.

Then !G and then write

perl -p -e 's/\n//g'

vim will replace the entire buffer with the output of the perl script.

See this link :