From: Brian Candler <b.candler@...>
Date: 2008-12-17T20:35:45+09:00
Subject: Re: ruby way of dumping file

Einar Magn炭s Boson wrote:
> p open(ARGV[0], "rb"){|f|f.read(20)}
> 
> but I don't think read(20) is guaranteed to read 20 bytes but maybe
> that is just in sockets.

In Ruby, I believe it's guaranteed to read 20 bytes, from both files and 
sockets - it will restart the underlying OS calls if necessary - unless 
EOF is reached.

I think the each_byte approach is cleanest, but here are some 
alternatives:

# not ruby-1.9 clean
puts File.read(ARGV[0],20).gsub(/(.)/) { "0x%02x\n" % $1[0] }

# different output format
puts File.read(ARGV[0],20).unpack("H*")[0].scan(/../).join(" ")
puts File.read(ARGV[0],20).unpack("H2 "*20).join(" ")
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