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| Ruby user's guide | Getting Started |

First, you'll want to check whether ruby is installed. From the shell prompt (denoted here by "`%`", so don't 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 1.6.6 (2001-12-26) [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 works slower than `cat`):

    % ruby -pe 0 file

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