Converting an Integer to a Hexadecimal String in Ruby

Converting an integer to a hexadecimal string in Ruby

You can give to_s a base other than 10:

10.to_s(16)  #=> "a"

Note that in ruby 2.4 FixNum and BigNum were unified in the Integer class.
If you are using an older ruby check the documentation of FixNum#to_s and BigNum#to_s

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

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.

Convert a hex string to a hex int

You'd need supply integer base argument to String#to_i method:

irb> color = "0xFF00FF"
irb> color.to_i(16)
=> 16711935
irb> color.to_i(16).to_s(16)
=> "ff00ff"
irb> '%#X' % color.to_i(16)
=> "0XFF00FF"

Convert Integer in Hex String Notation into a signed 8-Bit Integer

The c directive comes very close but it expects a different input: a single character representing the signed 8-bit integer. This requires the input "0xff" to be "\xff". So this conversion must take place first. At least one method known by you can be used here; the other one is Integer#chr:

"0xff".hex.chr # => "\xFF"

And the complete solution:

"0xff".hex.chr.unpack1(?c) # => -1

Decimal to hexadecimal conversion

Fixnum#to_s

255.to_s(16) # => "ff"

Convert string to hexadecimal in Ruby

Change this line:

line = a.map { |b| ", #{b}" }.join

to this:

line = a.map { |b| sprintf(", 0x%02X",b) }.join

(Change to %02x if necessary, it's unclear from the example whether the hex digits should be capitalized.)

Converting a hexadecimal string to a decimal number

Just use String#to_i with a base of 16:

"1a2f".to_i(16) # => 6703

convert decimal to hexidecimal 2 digits at a time Ruby

You can use String#gsub with a regular expression and Kernel#sprintf:

"01 67 15 06 01 76 61   73".gsub(/\d{2} */) { |s| sprintf("%02x", s.to_i) } 
  #=> "01430f06014c3d49"

The regular expression /\d{2} */) matches two digits followed by zero or more spaces (note 73 is not followed by space).

The result of the block calculation replaces the two or three characters that were matched by the regular expression.

sprintf's formatting directive forms a sting containing 2 characters, padded to the left with '0''s, if necessary, and converting the string representation of an integer in base 10 to the string representation of an integer in base 16 ('x').

Alternatively, one could use String#% (with sprintf's formatting directives):

"01 67 15 06 01 76 61   73".gsub(/\d{2} */) { |s| "%02x" % s.to_i } 
  #=> "01430f06014c3d49"

Convert byte array to hex string

This works:

[1, 1, 65, -50].map { |n| '%02X' % (n & 0xFF) }.join

The %02X format specifier makes a 2-character-wide hex number, padded with 0 digits. The & 0xFF is necessary to convert your negative numbers into the standard 0 through 255 range that people usually use when talking about byte values.

Convert binary string to hexadecimal in Ruby

You can convert it to an integer first, hinting that the string is binary (to_i(2)), then to hexadecimal (to_s(16)

"1010".to_i(2).to_s(16) # => 'a'

If you need it in uppercase, you can call upcase on the resulting string.

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