如何从Perl中的命令行参数计算文件的大小

Question

I was trying out a sample program that can calculate the size of the file given in command line arguments. It gives the size correctly when I have a file name stored inside a variable, but doesn't output a result when got the filename from the command line arguments.

#! /usr/bin/perl 
use File::stat;

while(<>){
 if(($_ cmp "\n") == 0){
   exit 0;
 }
 else{
   my $file_size =  stat($_)->size; # $filesize = s $_;
   print $file_size;
 }
}

I get no output when using file test operator -s and I get errors when using stat module:

Unsuccessful stat on filename containing newline at /usr/share/perl/5.10/File/stat.pm line 49, <> line 1.
Can't call method "size" on an undefined value at 2.pl line 17, <> line 1.

1.txt is the filename I'm giving as an input.

Answer 1

#!/usr/bin/perl 

for (@ARGV){
  my $file_size = -s $_;
  print $file_size;
}

or similar cmd oneliner,

perl -E 'say "$_, size: ", -s for @ARGV' *

Answer 2

#!/usr/bin/perl -w

$filename = '/path/to/your/file.doc';
$filesize = -s $filename;
print $filesize; 

Simple enough, right? First you create a string that contains the path to the file that you want to test, then you use the -s File Test Operator on it. You could easily shorten this to one line using simply:

print -s '/path/to/your/file.doc';

Also, keep in mind that this will always return true if a file is larger than zero bytes, but will be false if the file size is zero. It makes a handy and quick way to check for zero byte files.