I need:
"ff".hex.chr #=> "\xff"
but instead I get:
"ff".hex.chr #=> "\377"
Where is my mistake? What is missing? Environment is HBase 0.98.6 shell, which seems to be based on JRuby 1.6.8 console.
"\xff" and "\377" are different representations of the same data:
"\xff" is hexdecimal, and is typical of newer Ruby versions."\377" is octal, and is typical of older Ruby versions.You can see how the same number produces different strings:
printf("%o",255) #=> "377"
printf("%x",255) #=> "ff"
The default representation is a typically due to your console settings and Ruby version.
In general, do not rely on String#inspect to produce a consistent represenation, even on the same Ruby version. You can see this in action if you use some of the special characters:
"\007" #=> "\a"
The String#inspect method has altered the representation to neither octal nor hex.
If you're outputting to a system that requires a specific format, you can be explicit:
printf("\\x%x", 255) #=> \xff # lower case
printf("\\x%X", 255) #=> \xFF # upper case
You can also try the pack and unpack methods:
["ff"].pack("H*") #=> "\xFF"
If your string is always hex digits, and your desired output is just inserting "\x" in front of every two characters, then there's a fast solution:
print "a1b2c3".gsub(/../){"\\x#{$&}"}
#=> \xa1\xb2\xc3
A good quick introduction to Ruby string represenations and how to work with unprintable characters is in the Safari Books Ruby Cookbook