RUBY(1)

NAME
ruby - Interpreted scripting language

SYNOPSIS
ruby
  [-version
 ] [-c
 ] [-w
 ] [-d
 ] [-l
 ]
       [-p
 ] [-n
 ] [-a
 ] [-s
 ] [-0[digit]
 ]
       [-Kc
 ] [-escript
 ] [-Fpattern
 ]
       [-i[extension]
 ] [-Idir
 ] [-rfilename
 ]
       [-S
 ] [-v
 ] [-x[dir]
 ] [-X[dir]
 ] [-y ]
       [--
 ] [ programfile ] [ argument ] ...

PREFACE
Ruby is the interpreted scripting language for quick and easy object-oriented programming. It has many features to process text files and to do system management tasks (as in perl). It is simple, straight-forward, and extensible.

If you want a language for easy object-oriented programming, or you don't like the PERL ugliness, or you do like the concept of lisp, but don't like too much parentheses, ruby may be the language of the choice.

DESCRIPTION
Ruby's features are as follows:

• Interpretive
    Ruby is the interpreted language, so you don't have to recompile to execute the program written in ruby.

• Variables have no type (dynamic typing)
    Variables in ruby can contain data of any type. You don't have to worry about variable typing. Consequently, it has weaker compile time check.

• No declaration needed
    You can use variables in your ruby programs without any declarations. Variable name itself denotes its scope (local, global, instance, etc.)

• Simple syntax
    Ruby has simple syntax influenced slightly from Eiffel.

• No user-level memory management
    Ruby has automatic memory management. Objects no longer referenced from anywhere are automatically collected by the garbage collector built in the interpreter.

• Everything is object
    Ruby is the pure object-oriented language from the beginning. Even basic data like integers are treated uniformly as objects.

• Class, inheritance, methods
    Of course, as a O-O language, ruby has basic features like classes, inheritance, methods, etc.

• Singleton methods
    Ruby has the feature to define methods for certain specified object. For example, you can define a press-button action for certain GUI button by defining a singleton method for the button. Or, you can make up your own prototype based object system using singleton methods (if you want to).

• Mix-in by modules
    Ruby does not have the multiple inheritance intentionally. IMO, It is the source of confusion. Instead, ruby has modules to share the implementation across the inheritance tree. It is often called "Mix-in."

• Iterators
    Ruby has iterators for loop abstraction.

• Closures
    In ruby, you can objectify the procedure.

• Text processing and regular expression
    Ruby has bunch of text processing features like in perl.

• Bignums
    With bu ilt-in bignums, you can calculate factorial(400), for example.

• Exception handling
    As in Java(tm).

• Direct access to OS
    Ruby can call most of system calls on UNIX boxes. It can be used in system programming.

• Dynamic loading
    You can load object files into ruby interpreter on-the-fly, on most of UNIXes.

Command line options
Ruby interpreter accepts following command-line options (switches). Basically they are quite similar to those of Perl.

-0digit
    specifies the input record separator ($/) as an octal number. If no digits given, the null character is the separator. Other switches may follow the digits. -00 turns ruby into paragraph mode. -0777 makes ruby read whole file at once as a single string, since there is no legal character with that value.

-a  turns on auto-split mode when used with -n or -p. In auto-split mode, ruby executes
        $F = $_.split
    at beginning of each loop.

-c  causes ruby to check the syntax of the script and exit without executing. If there is no syntax error, ruby will print "Syntax OK" to the standard output.

-Kc specifies KANJI (Japanese character) code-set.

-d --debug
    turns on debug mode. $DEBUG will set TRUE.

-e script
    specifies script from command-line. if -e switch specified, ruby will not look for a script filename in the arguments.

-F regexp
    specifies input field separator ($;).

-i extension
    specifies in-place-edit mode. The extension, if specified, is added to old filename to make a backup copy. example:
        % echo matz > /tmp/junk
        % cat /tmp/junk
        matz
        % ruby -p -i.bak -e '$_.upcase!' /tmp/junk
        % cat /tmp/junk
        MATZ
        % cat /tmp/junk.bak
        matz

-I directory
    used to tell ruby where to load the library scripts. Directory path will be added to the load-path variable ($:').

-l  enables automatic line-ending processing, which means firstly set $ to the value of $/, and secondly chops every line read using chop!.

-n  causes ruby to assume the following loop around your script, which makes it iterate over filename arguments somewhat like sed -n or awk.
        while gets
          ...
        end

-p  acts mostly same as -n switch, but print the value of variable $_ at the each end of the loop. example:
        % echo matz | ruby -p -e '$_.tr! "a-z", "A-Z"'
        MATZ

-r filename
    causes ruby to load the file using [4]require. It is useful with switches -n or -p.

-s  enables some switch parsing for switches after script name but before any filename arguments (or before a --). Any switches found there is removed from ARGV and set the corresponding variable in the script. example:
        #! /usr/local/bin/ruby -s
        # prints "true" if invoked with `-xyz' switch.
        print "true\n" if $xyz

-S  makes ruby uses the PATH environment variable to search for script, unless if its name begins with a slash. This is used to emulate #! on machines that don't support it, in the following manner:
        #! /usr/local/bin/ruby
        # This line makes the next one a comment in ruby \
          exec /usr/local/bin/ruby -S $0 $*
    On some systems $0 does not always contain the full pathname, so you need -S switch to tell ruby to search for the script if necessary. To handle embedded spaces or such, A better construct than $* would be ${1+"$@"}, but it does not work if the script is being interpreted by csh.

-v --verbose
    enables verbose mode. Ruby will prints its version at the beginning, and set the variable `$VERBOSE' to TRUE. Some methods prints extra messages if this variable is TRUE. If this switch is given, and no other switches present, ruby quits after printing its version.

--version
    prints the version of ruby executable.

-w  enables verbose mode without printing version message at the beginning. It set the variable `$VERBOSE' to TRUE.

-x[directory]
    tells ruby that the script is embedded in a message. Leading garbage will be discarded until the first that starts with "#!" and contains string "ruby". Any meaningful switches on that line will applied. The end of script must be specified with either EOF, ^D (control-D), ^Z (control-Z), or reserved word __END__.If the directory name is specified, ruby will switch to that directory before executing script.

-X directory
    causes ruby to switch to the directory.

-y --yydebug
    turns on compiler debug mode. ruby will print bunch of internal state messages during compiling scripts. You don't have to specify this switch, unless you are going to debug the ruby interpreter itself.

AUTHOR
 Ruby is designed and implemented by Yukihiro Matsumoto <matz@netlab.co.jp>.