Backquoting special characters

  1. Custom sort
  2. Custom search
  3. The current script

Go ahead and look up songs from the album “4”:

./show --album 4 songs.txt

You’ll end up getting about 100 songs from all albums that include the number “4” in the album title. Currently, our searches look for the search text anywhere in the album name, song title, or artist name. What if we specifically want only the albums with that exact name? Let’s add a switch called “exact”:

} elsif ($switch eq "exact") {
$exact = 1;

We can implement this immediately after “if (%switches) {“:

#the first item on the command line is what we're searching for

#if we're looking for exact matches, set them up ahead of time
if ($exact) {
foreach $search (keys %searches) {
$searchText = $searches{$search};
$searches{$search} = "^$searchText\$";

We done all of this before except for the “\$”. It just goes through the keys of %searches, and adds “^” to the beginning of the search text and “$” to the end. But within Perl texts the dollar sign means something special. It means replace this with the variable whose name follows. It doesn’t matter that the variable that follows doesn’t exist, because Perl brings variables into existence the moment they’re used.

So, what we do is “backquote” the dollar sign. A backquote in front of a special character tells Perl not to interpret the special character, but rather to leave it as is. You can even backquote backquotes: "\\n" will not be a new line, it will be a backquote and the letter “n”.

You’ll do the same if you need to put a double-quote inside of double-quoted text. Backquote the “"” character. Instead of ending the text, Perl will insert the “"” into the text at that point:

$mobster = "Johnny \"Ratface\" Martin";

Don’t forget to add it to the help:

print "\t--exact: the search text must match exactly\n";

As an exercise, you might consider adding a “beginswith” and an “endswith” switch, to match albums, songs, and artists that begin or end with a specific text.

  1. Custom sort
  2. Custom search
  3. The current script