Perl script help

[toolman]

Hi there,

 

I am trying to fix a bug in a Perl script.

 

Can someone explain what the below code does/would do?

 

while (my $a = readdir(DIR)){

    if($a =~ m/(.+?)_(air)?port/ && $a !~ m/featured_(air)?port/ && $a !~ m/london_airport/i && $a !~ m/glasgow/ && $a !~ m/_opt/i){

        push(@dirs,$a);

    }

}

 

Thanks

[Irate]

Your human-readable code would be something like this.

 

"While we can still read files from this directory, loop through them; then, if it matches the expression m/(.+?)_(air)?port/ but does not match the other ones, push the current file into the array 'dirs'."

[dalecosp]

Bingo ... you beat me.  Although the last part should probably say "push the name of the current directory into the array 'dirs'".

[toolman]

Thanks.

 

What does the

m/(.+?)

part mean as there are also other

m/

 

 

m/(.+?)_(air)?port/

 

also, does the script mean if the files are broken/missing, it will revert to london_airport?

 

I'm not sure if that makes sense.

 

Thanks

[dalecosp]

m/ is "multiline mode".  

https://courses.cs.washington.edu/courses/cse190m/12sp/cheat-sheets/php-regex-cheat-sheet.pdf

 

 

 

also, does the script mean if the files are broken/missing, it will revert to london_airport?

Not sure what you mean, either.  It will create a list (array) of dirnames that have to do with airports, but not featured airports or London airport, or Glasgow or any dir with "opt" in it, more or less. Edited November 19, 2013 by dalecosp

[Irate]

Those expressions with m/(.+?)_/ and others are regular expressions.

The prefix m is for multiline mode, as dalecops pointed out previously.

 

There are many guides to understand regular expressions, but they are pretty complex subjects and even though I've been trying to for the past months, I haven't completely understood everything about them.