Ruby: How to convert a list of integers into a hexadecimal string?

Question

I have an array of integers that range from 0 to 255, each representing two hexadecimal digits. I want to convert this array into one hexadecimal string using Ruby. How would I do that?

Answer 1

With pack and unpack: (or unpack1 in Ruby 2.4+)

[0, 128, 255].pack('C*').unpack('H*')[0]
#=> "0080ff"

[0, 128, 255].pack('C*').unpack1('H*')
#=> "0080ff"

The actual binary hexadecimal string is already returned by pack('C*'):

[0, 128, 255].pack('C*')
#=> "\x00\x80\xFF"

unpack('H*') then converts it back to a human readable representation.

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A light-weight alternative is sprintf-style formatting via String@% which takes an array:

'%02x%02x%02x' % [0, 128, 255]
#=> "0080ff"

x means hexadecimal number and 02 means 2 digits with leading zero.