Searching a file name using regex and glob variable - regex

Question

I have a requirement to find a file name display a text if it is present and below is the code I am using
use strict;
use warnings;
use feature "say";
my #arr={"file1*.gz","file2*.gz"};
foreach my $file (#arr) {
my $file1=glob ("$file");
say "$file1";
if (-e $file1) {
say "File Generated using script";
}
}
When I use the below code, I am able to get 1st element of array properly, but for the 2nd element, I am seeing below error:
Use of uninitialized value $file1 in string
And if the size of the array is 1, then it is working properly.
I am not sure what's going wrong in the above code.

Answer 1

There is a problem with this line:
my #arr={"file1*.gz","file2*.gz"};
I think you meant to use parentheses instead of curlies to create your array; what you have is a hash reference.
There is also a problem with this line:
my $file1=glob ("$file");
Instead of returning a file name, glob returns undef the second time because you are using it in scalar context and:
In scalar context, glob iterates through such filename expansions,
returning undef when the list is exhausted.
You can use glob in list context, which can be enforced with parentheses around $file:
use strict;
use warnings;
use feature "say";
my #arr = ("file1*.gz", "file2*.gz");
foreach my $file (#arr) {
my ($file1) = glob($file);
say $file1;
if ( -e $file1 ) {
say "File Generated using script";
}
}
This code grabs only the 1st file name that matches your wildcard. If you want all files that match, you need to add another for loop.

Answer 2

You are not using all the power of the glob function. As toolic says, you are also using curly braces {} wrong -- they create a hash reference, not a list.
Your options in normal array assignment are typically:
my #arr = ('foo', 'bar'); # parenthesis
my #arr = qw(foo bar); # "quote word", basically a string split on space
But this is not relevant to the answer to your question: How to find the names of files that exist that match the glob expression.
First off, the argument to glob can contain several patterns, separated by space. For example, from the documentation perldoc -f glob:
...glob("*.c *.h") matches all files with a .c or .h extension.
You should read the entire documentation, it is very enlightening, and core Perl knowledge.
So you do not need to loop around your number of glob patterns, just concatenate them. E.g.
my $globs = "file1*.gz file2*.gz"; # two patterns at once
But there is more. You can use curly braces in globs, creating an alternation. For example, {1,2} will create two alternations with 1 and 2 respectively, so we can simplify your expression further
my $globs = "file{1,2}*.gz"; # still two patterns at once
And there is more. You do not need to store these glob patterns in an array and loop over it, you can just loop over the glob result itself. E.g.
for my $file (glob $globs) { # loop over globs
You also do not need to check if a file exists with -e, as the glob already takes care of that check. If the glob does not return a file name, it was not found. It works much the same as using globs on the command line in bash.
So in short, you can use something like this:
use strict;
use warnings;
use feature "say";
foreach my $file (glob "file{1,2}*.gz") {
say "File '$file1' found";
}

Answer 3

Perhaps OP intended something of following kind
use strict;
use warnings;
use feature 'say';
my #patterns = qw/file1*.gz file2*.gz/;
for my $pat (#patterns) {
say 'Pattern: ' . $pat;
for my $fname ( glob($pat) ) {
say "\t$fname :: File Generated using script" if -e $fname;
}
}