Command line options - ruby

Question

I am confused about Ruby command-line options. Both -C dir and -X dir remove directory, but how do they differ from each other?
How does -x [dir] differ from -X dir?
What does -I dir do (I know that it adds dir as the directory for loading libraries)?

Answer 1

Let's create a test.rb file in home directory with following:
hello
#!/usr/bin/ruby
p "here"
Now if we try to run it:
ruby -C /home/my_home test.rb
Which means change working directory to /home/my_home and run test.rb you will get an error:
test.rb:1:in `<main>': undefined local variable or method `hello' for main:Object (NameError)
If we run it with:
ruby -x /home/my_home test.rb
We will get "here" printed and get no error. The main difference between -x and -C is that -x removes everything before the #!/usr/bin/ruby line. And you don't have to set directory to cd too, when using -x. Because the main purpose of -x is to remove lines and it just includes -C functionality too, if needed.
cd /home/my_home; ruby -x test.rb
See (ruby --help)
-Cdirectory cd to directory, before executing your script
-x[directory] strip off text before #!ruby line and perhaps cd to directory
As for -I. You can provide the directories that ruby will search for the file you execute or require.
ruby -x test.rb
Ruby will not find the test.rb file unless you are in /home/my_home. But if you add -I ruby will look for test.rb in "/home/my_home" too.
ruby -x -I/home/my_home test.rb
The difference with -C is that it will not change directory before executing, but will just search for files there.

Answer 2

As you can see from man ruby or some docs online, -C and -X is the same.
And -I will add some dir to ruby LOAD_PATH. For example, I have ./a/my.rb and `./test.rb' like this:
# ./a/my.rb
def hello
puts 'hello from a/my'
end
# ./test.rb
require 'my'
hello
And I execute ruby -I ./a test.rb. This will print hello from a/my. Without -I, ruby will report an error: cannot load such file -- my, because ./a is not in current LOAD_PATH.

Answer 3

-C and -X options do the same job (Changes directory before executing). There is no difference.
-I option is used for adding path to $LOAD_PATH
For example: Assume you have ruby file called my_print_class.rb in my_lib directory
my_print_class.rb:(~/my_lib/my_print_class.rb)
class MyPrintClass
def self.my_print(str)
puts str
end
end
Now you have my_call.rb in home(~).
~/my_call.rb:
require 'my_print_class'
MyPrintClass.my_print("Hello world")
For this you need path of my_print_class so you use ruby -I my_lib my_call.rb
http://www.tutorialspoint.com/ruby/ruby_command_line_options.htm