Here are some of the things I spotted in your wanted sub. open temp_file_cy, "$File::Find::name;

1. I think you want to use a lexical variable my $temp_file_cy instead of a bareword temp_file_cy as your file-handle
2. then, "$File::Find::name has only one quote at the beginning.
3. If you may, use 3 agrument open function, then check error if file is not opened
4. I will advise you use warnings and strict in your script. As it shows several 'mis-typed' variables. It will help alot

thanks for your kind reply.

a) in fact I insert"use warnings" and "use strict" in my code. I just omitted them for simple demo of my code. And in my real code I didn't miss quote, it is a type error here. Any way, thanks for your kind remind.

b) accroding to your ideas,I use

open $temp_file_cy, "$File::Find::name"

it is interesting that I haven't see "open $filehandle ...", but always "open filehandle ...". in the text book. Can you tell me the difference between them? thanks.

c) I have checked the attributes of those files, they are all -rw-rw----, so I guess "-r " should be ok here. In fact what I want to do really is this:

 my @matching = grep {/$pattern/} <temp_file_cy>;

I always get this message: " readline() on unopened filehandle temp_file_cy at ../cy_find line 99", which make me to insert code "-r temp_file_cy" to see what happened

can you give me some help on this? thanks

Maybe there was an error in opening the file. Try autodie or check for errors like this:

unless (open my $filehandle,"<",$File::Find::name) {
 warn $!;
 return;
}
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Sorry if my advice was wrong.

Why do you open the file just to close it again? You know -r can take a file name, not just a file handle, right?

Putting variables in quotes when you don't need to may bite you in future when you get to using references. But maybe you won't put variables containing references in quotes and so it is just a style issue.

But the main problem with your code is that $File::Find::name will often not be useful for opening a file (nor for checking the permissions on a file).

If you call File::Find's find() and pass it "foo" as the directory to search, then find() will chdir into the "foo" directory (by default) before doing much of any work. If you have a file "foo/bar", then your 'wanted' subroutine will be called with $_ set to "bar" and $File::Find::name set to "foo/bar".

Since your program is now cd'd into "foo", trying to open "foo/bar" would only work if you also had a "foo/foo/bar" file. So try:

sub wanted {
    print "hello 1\n"
        if -r $_;
}
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thank you for your reply. I tried your code and it WORKS! thank you very much and thanks for every one who had replied my questions.

by the way, I would like to do some operation to the file, I tried some code like this:

 print "hello 1\n" if (-r $_);
 my @matching = grep {/$my_pattern/} <$_>;
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I failed with this code. I have to

 open $filehandle,"<", $_" or die .... 
 my @matching = grep {/$my_pattern/} <$_>;
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did I do something wrong? or is there any better way to do grep or similar operateion in the $_? thanks.

Use File::Slurp to read a file in one command.
Sorry if my advice was wrong.

thanks for your reply. I have checked the attributes and they are -rw-rw----. Thanks.