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 Ruby user's guide Getting started  

First, you'll want to check whether ruby is installed.  From the shell prompt (we denote a shell prompt by "", so you should not type the ""), type

% ruby -v

(-v tells the interpreter to print the version of ruby), then press the Enter key.  If ruby is installed, you will see a message something like the following:

 % ruby -v
 ruby 1.4.6 (2000-08-16) [i586-linux]

If ruby is not installed, you can ask your administrator to install it,  or you can do it yourself, since ruby is free software with no restrictions on its installation or use.

Now, let's play with ruby.  You can place a ruby program directly on the command line using the -e option:

 % ruby -e 'print "hello world\n"'
 hello world

More conventionally, a ruby program can be stored in a file.

 % cat > test.rb
 print "hello world\n"
 ^D
 % cat test.rb
 print "hello world\n"
 % ruby test.rb
 hello world

^D is control-D.  The above is just for UNIX.  If you're using DOS, try this:

 C:\ruby> copy con: test.rb
 print "hello world\n"
 ^Z
 C:\ruby> type test.rb
 print "hello world\n"
 C:\ruby> ruby test.rb
 hello world

When writing more substantial code than this, you will want to use a real text editor!

Some surprisingly complex and useful things can be done with miniature programs that fit in a command line.  For example, this one replaces foo with bar in all C source and header files in the current working directory, backing up the original files with ".bak" appended:

 % ruby -i.bak -pe 'sub "foo", "bar"' *.[ch]

This program works like the UNIX cat command (but is slower than cat):

 % ruby -pe 0 file

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