I thought we could kick things off with something simple but\nhandy. This week I'm going to do a short series on quoting and\nliterals.\n
\n\nYou probably already know a lot of the literal syntax in Ruby. Stuff\nlike literal integers, floating point numbers, and strings.\n
\n\n\n\n42\n3.14159\n\"foo\"\n\n\n\n\nYou probably also know that like many languages, Ruby has a literal\nsyntax for hexidecimal and octal numbers:\n
\n\n\n\n0x7FFF
# =>
32767\n0755 # => 493\n\n\n\n\nOctal numbers are useful for things like specifying unix file\npermissions.\n
\n\n\n\nrequire 'fileutils'\ninclude FileUtils\n\nchmod 0755, 'somefile'\n\n\n\n
\nRuby also supports a slightly less common type of integer literal:\nbinary literals. I don't know about you, but even after all these\nyears of UNIX I still have some trouble translating octal numbers into\npermissions, and vice-versa, in my head. This is one place binary\nliterals can come in handy.\n
\n\nLet's take a look at the previous example, only using a binary literal\nthis time. First, we'll start with a reminder of the order of\npermissions bits. From left to write, we have permissions for user,\ngroup, and other.\n
\n\n\n\n# U G O\n# rwxrwxrwx\n\n\n\n
\nNow underneath that, we'll spell out our permission mask as a binary\nliteral.\n
\n\n\n\n# U G O\n# rwxrwxrwx\n0b111101101\n\n\n\n
\nJust to check, we'll translate that to octal form.\n
\n\n\n\nperms = 0b111101101\nperms.to_s(8) # => \"755\"\n\n\n\n
\nNow with our permissions mask in hand, we can set permissions,\nconfident that we've set the desired bits.\n
\n\n\n\nchmod
perms, 'somefile'\n\n\n\n\nAnd that's it for today. Happy hacking!\n
Copyright © 2012 ShipRise and Avdi Grimm.
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