Simple Hex Viewer (My First Ruby!)

# My First Ruby - I LOVE HEX!
# Large file will get slow speed.
# I guess I should use File.open for such a case.

if ARGV.length == 0 then
    puts "No file input"
    exit 1
end

if File.exist?(ARGV[0]) then
    printf "%s (%d bytes)\n", ARGV[0], File.size(ARGV[0])
else
    STDERR.printf "No such file: %s\n", ARGV[0]
    exit 1
end

Align = 16
offset = 0
dump_s = ""
File.binread(ARGV[0]).bytes { |c|
    if offset % Align == 0 then
        printf "%08X: ", offset
    end

    printf "%02X", c

    offset += 1
    print " "
    if /[[:print:]]/ === c.chr then
        dump_s << c
    else
        dump_s << "."
    end

    if offset % 16 == 0 then
        puts " " << dump_s
        dump_s = ""
    end
}
if offset % Align != 0 then
    puts "   " * (Align - (offset % Align)) << " " + dump_s
end