From: Mike Stok <mike@...>
Date: 2002-09-11T22:56:51+09:00
Subject: Re: Is there a "get" function for words and dwords?

In article <9ba6a8da.0209110515.4b63b152@posting.google.com>, Khurram wrote:
> The sysread returns a string... I want the actual binary value.
> 
> Is there a way to do this conversion?

[Sorry if this is a duplicate, I fat fingered something...]

Unpack e.g.

[mike@rand mike]$ od -c /bin/ls | head -1
0000000 177   E   L   F 001 001 001  \0  \0  \0  \0  \0  \0  \0  \0  \0

so the first two bytes are 0x7F and 0x45 (the ASCII value for E)

irb(main):001:0> f = File.new('/bin/ls', 'r')
#<File:/bin/ls>
irb(main):002:0> bytes = f.sysread(2)
"\177E"
irb(main):003:0> bytes.unpack('n')
[32581]
irb(main):004:0> bytes.unpack('v')
[17791]

The difference between 'n' and 'v' in the template is the byte ordering
used - 'n' is network (or big-endian) order, 'v' is little endian.  The
values here are 0x7F45 and 0x457F

Unpack returns an array because it can be used to unpack many things
at once.

Hope this helps,

Mike

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