Question

I need to print escaped characters to a binary file using Ruby. The main problem is that slashes need the whole byte to escape correctly, and I don’t know/can’t create the byte in such a way.

I am creating the hex value with, basically:

'\x' + char 

Where char is some ‘hex’ value, such as 65. In hex, \x65 is the ASCII character ‘e’.

Unfortunately, when I puts this sequence to the file, I end up with this:

\\x65 

How do I create a hex string with the properly escaped value? I have tried a lot of things, involving single or double quotes, pack, unpack, multiple slashes, etc. I have tried so many different combinations that I feel as though I understand the problem less now then I did when I started.

How?

Answer 1

Okay, if you want to create a string whose first byte has the integer value 0x65, use Array#pack

irb> [0x65].pack('U') #=> 'e' irb> 'e'[0] #=> 101 

101₁₀ = 65₁₆, so this works.

If you want to create a literal string whose first byte is ‘\’, second is ‘x’, third is ‘6’, and fourth is ‘5’, then just use interpolation:

irb> '\\x#{65}' #=> '\\x65' irb> '\\x65'.split('') #=> ['\\', 'x', '6', '5']