Question

I have a program expecting input from stdin, OR from a mix of .log and .log.gz files. Here are the three types of calls I want the program to handle:

cat input.log | prog
prog < input.log
prog input.log input.log.gz

The program considers all input files as one. I was hoping to capitalize on ARGV to process all input uniformly:

while (<>) {
# process input
}

My goal is to process gz files in the same loop. How can this be done? I want to know how messy it is. If it is too bad I will handle gz separately.

I can only use core modules with Perl 5.8.8.

Answer 1

You can’t really do that and get the shorthand benefit of the diamond operator.

• Because you’re going to have to monkey with the input handle, you’re going to need to open the files yourself.

• You might be able to use @ARGV for this, but you’ll only get the easy handling if you reopen *::STDIN for these files.

  my $file = shift;
  if    ( !$file )           {} # use STDIN as is.
  elsif ( $file =~ /\.gz$/ ) { 
      open( ::STDIN, '-|', "gunzip $file" ) or die "Could not open: $!!";
  }
  else {
      open( ::STDIN, '<', $file ) or die "Could not open $file: $!!";
  }
  
  while ( <> ) { 
      ...
  }
  close STDIN;