print "Options for this program:\n-f --file for input file default= bonds.trj\n-a --atoms atom types (in correct order and input separately) default= @test\n";
exit;
}
open INPUT, "<$in_file" or die "Cannot open $in_file: $!";
open OUTPUT, ">frac.dat" or die "Cannot open output file: $!";
if(@atoms) {
@test = @atoms;
}
print "Input for this run:\n Input file = $in_file\n Atom types = @test\n";