Is there a way to do matching pattern using array in perl?

Question

For example,

@seed = ('seed_1', 'seed_2', 'seed_3', 'seed_4);

However, in the future there could be more than seed_4. How can I make this as general as possible? Meaning I don't have to manually write the future seed_. It can be 'seed_50' or random values.

example:

$file ='text.txt';
for my $seed (@seed)
 {
   if (open my $data, "<", $file)
    {
      my $line =<$data>;
      print "ERROR: $line\n";
    }
   close $data;
}

the seed_ are actually folders in directories. So, I need to go through every seed to open the text file but I may not know the values in every seed folder. The dir are directories I need to open. I just need to read out the first line of the text.

so for example:

for my $dir (@dir){
    for my $seed (@seed)
     {
       if (open my $data, "<", $file)
        {
          my $line =<$data>;
          print "ERROR: $line\n";
        }
       close $data;
    }
}

@ikegami I have @array = ('seed_1', 'seed_2', 'seed_3', 'seed_4');. But in the future, there may be more than this. Is there a way to automatically match the pattern without writing out manually the seed_ ? — Alyssa Low
– Alyssa Low, Commented Oct 20, 2020 at 3:29
Thank you for editing and adding an example. Can you add more to show how is regex with @seed elements involved? (Do you mean to test whether any of $seed matches, for each $line? Or something else?) — zdim
– zdim, Commented Oct 20, 2020 at 4:51
(I mean even just adding a comment to the code would clarify it (like # check whether $seed matches $line or some such) — zdim
– zdim, Commented Oct 20, 2020 at 5:13
Your example doesn't use $seed?!? Did you use $file where you meant to use $seed? If so, you want glob("\Q$dir\E/seed*") — ikegami
– ikegami, Commented Oct 20, 2020 at 6:13

zdim · Accepted Answer · 2020-10-20 03:16:43Z

5

Escape possible non-"word" ASCII characters in the array elements using quotemeta, and build a pattern with them using alternation

my $pattern = join '|', map { quotemeta } @ary;

Then use this $pattern in a regex pattern

if ( $string =~ /$pattern/ ) { say $& }

to find the first of elements that matches in the $string (if any), or

while ( $string =~ /$pattern/g ) { say $& }

to iterate over all matches, etc.

Depending on the details it may be necessary to sort the array first.

edited Oct 20, 2020 at 3:16

answered Oct 20, 2020 at 2:16

zdim

67.2k5 gold badges59 silver badges87 bronze badges

Sign up to request clarification or add additional context in comments.

6 Comments

Alyssa Low Over a year ago

Hi, thank you for suggesting this. I tried it and it works. However, if my array increases such as there are seed_1 till seed_10 or random numbers behind seed_, do i have to manually type it out in the @seed?

zdim Over a year ago

@AlyssaLow No, you never need to type specific elements; that is the point. The code never names what is in the array -- the whole array is used, whether it has two elements or a thousand. The map applies quotemeta (which escapes special characters if there are any) to every element of whatever list you give it, then all those are join'-ed with |. The only specific item to provide is the array name (@seed in your case instead of @ary here)

zdim Over a year ago

@AlyssaLow The code uses the array (@seed in your case) with all its elements. The array itself has to be formed somehow elsewhere in the code; either you type in those elements, read them from a file, compute them at runtime ... it depends on how your program operates.

Alyssa Low Over a year ago

Ohh okay, thank you for the explanation. I'll give it a try.

mpapec Over a year ago

Any benefits of making a compiled regex? my ($pattern) = map { qr/$_/ } ..

|

Collectives™ on Stack Overflow

Is there a way to do matching pattern using array in perl?

1 Answer 1

6 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

6 Comments

Your Answer

Sign up or log in

Post as a guest

Related