Following are some things I found in my collection of obscure Ruby. So, in Ruby, a simple no-bells implementation of the Unix command cat would be: #!/usr/bin/env ruby puts ARGF.read ARGF is your friend when it comes to input; it is a virtual file that gets all input from named files or all from STDIN. … Read more
It’s always enlightening to do a benchmark on the various suggested answers. Here’s what I found out: #!/usr/bin/ruby require ‘benchmark’ ary = [] 1000.times { ary << {:bar => rand(1000)} } n = 500 Benchmark.bm(20) do |x| x.report(“sort”) { n.times { ary.sort{ |a,b| b[:bar] <=> a[:bar] } } } x.report(“sort reverse”) { n.times { ary.sort{ … Read more
Just look at the docs: require_relative complements the builtin method require by allowing you to load a file that is relative to the file containing the require_relative statement. For example, if you have unit test classes in the “test” directory, and data for them under the test “test/data” directory, then you might use a line … Read more
There are many ways to do this, one is reject noEmptyCities = cities.reject { |c| c.empty? } You can also use reject!, which will modify cities in place. It will either return cities as its return value if it rejected something, or nil if no rejections are made. That can be a gotcha if you’re … Read more
Original Answer The problem mainly occurs after updating OS X to El Capitan (OS X 10.11) or macOS Sierra (macOS 10.12). This is because of file permission issues with El Capitan’s or later macOS’s new SIP process. Try changing the permissions for the /usr/local directory: $ sudo chown -R $(whoami):admin /usr/local If it still doesn’t … Read more
It is the ternary operator, and it works like in C (the parenthesis are not required). It’s an expression that works like: if_this_is_a_true_value ? then_the_result_is_this : else_it_is_this However, in Ruby, if is also an expression so: if a then b else c end === a ? b : c, except for precedence issues. Both are … Read more
sentence.sub! ‘Robert’, ‘Joe’ Won’t cause an exception if the replaced word isn’t in the sentence (the []= variant will). How to replace all instances? The above replaces only the first instance of “Robert”. To replace all instances use gsub/gsub! (ie. “global substitution”): sentence.gsub! ‘Robert’, ‘Joe’ The above will replace all instances of Robert with Joe.
Your question is wrong, so to speak. What’s happening here isn’t “ampersand and colon”, it’s “ampersand and object”. The colon in this case is for the symbol. So, there’s & and there’s :foo. The & calls to_proc on the object, and passes it as a block to the method. In Ruby, to_proc is implemented on … Read more
Another important but subtle difference between procs created with lambda and procs created with Proc.new is how they handle the return statement: In a lambda-created proc, the return statement returns only from the proc itself In a Proc.new-created proc, the return statement is a little more surprising: it returns control not just from the proc, … Read more
I’d like to expand & clarify chaos’s answer a bit. If you surround your command with backticks, then you don’t need to (explicitly) call system() at all. The backticks execute the command and return the output as a string. You can then assign the value to a variable like so: output = `ls` p output … Read more