Perl loop through text files in a directory, locate file based on file name and print content - perl

Question

How do i loop through files in a directory, locate file based on file name and print file content?
Please see below code:
files in directory:
1234.txt
345.txt
234.txt
Code:
opendir (DIR, "LOCATION")|| die "cant open directory\n";
my #DATA = grep {(!/^\./)} readdir (DIR);
while ( my $file = shift #DATA) {
open FILE, "LOCATION";
while (FILE){
if ($file eq "235") {
print $_;
}
}
}

Answer 1

This should do (untested):
opendir( DIR, "/path/to/dir" );
while ( my $entry = readdir( DIR ) ) {
if ( $entry =~ /^$filenameImLookingFor$/ ) {
open( FILE, "$entry/$filenameImLookingFor" );
my #lines = <FILE>;
close( FILE );
print( join( '', #lines );
}
}
closedir( DIR );

Answer 2

The code in your question:
opendir (DIR, "LOCATION")|| die "cant open directory\n";
my #DATA = grep {(!/^\./)} readdir (DIR);
while ( my $file = shift #DATA) {
open FILE, "LOCATION";
while (FILE){
if ($file eq "235") {
print $_;
}
}
}
Will do this:
First it will handily find all files in directory "LOCATION" that do not begin with a period. Then it will iterate in a rather odd loop over each file name. The normal version of this loop would be:
for my $file (#DATA)
Then it will attempt to open the directory "LOCATION" again. This will likely fail, because "LOCATION" is a directory. Since you do not check the return value with die, this error will be silent.
What you probably want is to use
if ($file eq "235.txt") {
open my $fh, "<", $file or die $!;
print <$fh>;
}
This part:
while (FILE)
Is not actually checking the return value of readline(), it is checking whether the file handle is returning a true value. As near as I can tell on my system, it does return a true value even if the open failed. Which means of course that the loop will run indefinitely. What you probably meant was
while (<FILE>)
However, as explained earlier, this will only result in the error "readline() on unopened file handle FILE" since the open statement cannot open a directory.
Your check
if ($file eq "235")
Will never be true, since you said your file names had a .txt extension. You might instead do
if ($file eq "235.txt")
Which should work.
If you wanted to be clever, you could include your check directly in the grep:
my #files = grep { $_ eq "235.txt" } readdir DIR;
And since perl can use the <> diamond operator to print files listed in the #ARGV array, you can even do this
#ARGV = grep { $_ eq "235.txt" } #ARGV;
print <>;
Assuming you call the script with:
perl script.pl dir/*.txt
This is, of course, just the long version of doing:
perl -pe0 235.txt
Which is the long version of
cat 235.txt
So, I get the feeling you are trying to do something other than what your code implies.