newline character in comm perl script

Question

There is a newline character getting inserted between the 2 filenames. How do I avoid this?

$diff = `comm -3 "/tmp/${PATH1U}_${SITE1}_s_${USER} /tmp/${PATH2U}_${SITE2}_s_${USER}"|wc -l`;

This is the error message while executing:

comm: missing operand after `/tmp/file1\n /tmp/file2\n'

Answer 1

Two problems:

• $USER's value ends with a newline. You can chomp it away. Fix:

  chomp($USER);
  

• You are passing one very long and incorrect path instead of two. Fix:

  `comm -3 '/tmp/${PATH1U}_${SITE1}_s_${USER}' '/tmp/${PATH2U}_${SITE2}_s_${USER}' | wc -l`
  

  But that's a hackish way of creating shell literals. Cleaner:

  use String::ShellQuote qw( shell_quote );
  
  my $comm_cmd = shell_quote('comm', '-3',
     "/tmp/${PATH1U}_${SITE1}_s_${USER}",
     "/tmp/${PATH2U}_${SITE2}_s_${USER}");
  
  `$comm_cmd | wc -l`