From: Eric Wong <normalperson@...>
Date: 2011-09-10T10:32:59+09:00
Subject: Re: how to write data in binary to a file?

frank hi <yw_hi@163.com> wrote:
> I want to write the data into a file in binary mode. The file is opened
> in binary mode by ofile=File.open("filename",'wb'). However, when I
> write the data using ofile.write(1), ruby will write the ascii code 31
> to the file. I want it to write one byte number withe value 1. How can I
> do it? I have been googling a lot and could not find the answer.

You need to pack the data into a string before writing.  The following
will write one unsigned byte:

	buffer = [ 1 ].pack("C")
	file.write(buffer)

See `ri Array#pack` for full documentation on things you can do with
pack (and String#unpack for the inverse).

There are also a nearly-identical `pack'/`unpack' functions in Perl.
The "perlpacktut" manpage is a great read for this.

-- 
Eric Wong