I want to do:
File.open(path_to_file, “r”) do |f|
magic_number = f.read(8)
$stderr.print “Magic number is: #{magic_number}\n”
end
but I want to print the bytes as HEX values - how do I do that?
Thanks,
Wes
On Mar 21, 2006, at 11:28 PM, Wes G. wrote:
Wes
Use printf/sprintf/%
Ex:
puts “%#x” % 100 -> 0x64
– Daniel
On 3/21/06, Wes G. [email protected] wrote:
I want to do:
File.open(path_to_file, “r”) do |f|
magic_number = f.read(8)
$stderr.print “Magic number is: #{magic_number}\n”
endbut I want to print the bytes as HEX values - how do I do that?
You can do this with String.unpack. In the PickAxe 2 book, see table
27.14 “Directives for String#unpack”. In my copy, it’s on page 624.
Daniel,
Not to be obtuse, but what is the # sign for in the specification?
And what is the mod 100 -> 0x64 business about?
wg
Daniel H. wrote:
On Mar 21, 2006, at 11:28 PM, Wes G. wrote:
Wes
Use printf/sprintf/%Ex:
puts “%#x” % 100 -> 0x64– Daniel
Why do I have to read my bytes into a string and then convert them back?
Is there any way to read an array of bytes from my file?
WG
Daniel H. wrote:
On Mar 21, 2006, at 11:43 PM, Wes G. wrote:
Daniel,
Not to be obtuse, but what is the # sign for in the specification?
And what is the mod 100 -> 0x64 business about?
wg
Sorry, I misread your question. What you need is String#unpack. Do a
‘ri String#upack’. String#% is the format method. It’s function is
the same as printf. See Kernel#sprintf for a list of format options
(including #).– Daniel
Answer:
puts “Magic number is: #{magic_number.unpack(‘H*’)}”
Thanks for all the help.
Argh!
I sure wish there were a get_bytes() method on the File and/or IO
objects.
WG
Wes G. wrote:
Why do I have to read my bytes into a string and then convert them back?
Is there any way to read an array of bytes from my file?
WG
Daniel H. wrote:
On Mar 21, 2006, at 11:43 PM, Wes G. wrote:
Daniel,
Not to be obtuse, but what is the # sign for in the specification?
And what is the mod 100 -> 0x64 business about?
wg
Sorry, I misread your question. What you need is String#unpack. Do a
‘ri String#upack’. String#% is the format method. It’s function is
the same as printf. See Kernel#sprintf for a list of format options
(including #).– Daniel
On 21-Mar-06, at 6:20 PM, Wes G. wrote:
Why do I have to read my bytes into a string and then convert them
back?Is there any way to read an array of bytes from my file?
You can view a String as an array of character values:
---------------------------------------------------------- Class: String
A +String+ object holds and manipulates an arbitrary sequence of
bytes, typically representing characters. String objects may be
created using +String::new+ or as literals.
ratdog:~/tmp mike$ irb
irb(main):001:0> f = File.open(‘try.rb’, ‘r’)
=> #<File:try.rb>
irb(main):002:0> s = f.read(32)
=> “#!/usr/bin/env ruby\n\nBASENAMES =”
irb(main):003:0> s[0]
=> 35
irb(main):004:0> s[0].chr
=> “#”
irb(main):005:0> ‘0x%02x’ % s[0]
=> “0x23”
irb(main):006:0> s.unpack(‘H*’)
=> [“23212f7573722f62696e2f656e7620727562790a0a424153454e414d4553203d”]
Mike
And what is the mod 100 → 0x64 business about?
–
Posted via http://www.ruby-forum.com/.
–
Mike S. [email protected]
http://www.stok.ca/~mike/
The “`Stok’ disclaimers” apply.
To print a hexdump of the string to stdout, check out:
http://www.unixgods.org/~tilo/Ruby/hexdump.html
-keith
On Mar 21, 2006, at 11:43 PM, Wes G. wrote:
Daniel,
Not to be obtuse, but what is the # sign for in the specification?
And what is the mod 100 -> 0x64 business about?
wg
Sorry, I misread your question. What you need is String#unpack. Do a
‘ri String#upack’. String#% is the format method. It’s function is
the same as printf. See Kernel#sprintf for a list of format options
(including #).
– Daniel