ruby.1

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.\" $Id$
.\"
.na
.TH RUBY 1 "ruby 1.1" "22/Jun/98" "Ruby Programmers Reference Guide"
.SH NAME
ruby - interpreted object-oriented scripting language
.SH SYNOPSIS
.B ruby \c
  [ \c
.BI -version \c
 ]  [ \c
.BI -c \c
 ]  [ \c
.BI -w \c
 ]  [ \c
.BI -d \c
 ]  [ \c
.BI -l \c
 ]
       [ \c
.BI -p \c
 ]  [ \c
.BI -n \c
 ]  [ \c
.BI -a \c
 ]  [ \c
.BI -s \c
 ]  [ \c
.BI -0 "[digit]"\c
 ]
       [ \c
.BI -K "c"\c
 ]  [ \c
.BI -e "script"\c
 ]  [ \c
.BI -F "pattern"\c
 ] 
       [ \c
.BI -i "[extension]"\c
 ]  [ \c
.BI -I "dir"\c
 ] [ \c
.BI -r "filename"\c
 ]  
       [ \c
.BI -S \c
 ]  [ \c
.BI -v \c
 ]  [ \c
.BI -x "[dir]"\c
 ]  [ \c
.BI -X "[dir]"\c
 ]  [ \c
.BI -y \c
]
       [ \c
.BI -- \c
 ] [ programfile ]  [ argument ] ...
                                       
.SH 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.
.PP   
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.
.SH DESCRIPTION
Ruby's features are as follows:
.TP
.B "\(bu Interpretive"
Ruby is the interpreted language, so you don't have to
recompile to execute the program written in Ruby.
.TP
.B "\(bu 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.
.TP          
.B "\(bu No declaration needed"
You can use variables in your Ruby programs without any
declarations. Variable name itself denotes its scope (local,
global, instance, etc.)
.TP
.B "\(bu Simple syntax"
Ruby has simple syntax influenced slightly from Eiffel.
.TP
.B "\(bu 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.
.TP
.B "\(bu Everything is object"
Ruby is the pure object-oriented language from the beginning.
Even basic data like integers are treated uniformly as objects.
.TP
.B "\(bu Class, inheritance, methods"
Of course, as a O-O language, Ruby has basic features like
classes, inheritance, methods, etc.
.TP
.B "\(bu 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).
.TP
.B "\(bu 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 as "Mix-in."
.TP
.B "\(bu Iterators"
Ruby has iterators for loop abstraction.
.TP
.B "\(bu Closures"
In Ruby, you can objectify the procedure.
.TP
.B "\(bu Text processing and regular expression"
Ruby has bunch of text processing features like in perl.
.TP
.B "\(bu Bignums"
With built-in bignums, you can calculate factorial(400), for
example.
.TP
.B "\(bu Exception handling"
As in Java(tm).
.TP
.B "\(bu Direct access to OS"
Ruby can call most of system calls on UNIX boxes. It can be
used in system programming.
.TP
.B "\(bu Dynamic loading"
You can load object files into ruby interpreter on-the-fly, on
most of UNIXes.
.PP
.SH Command line options
Ruby interpreter accepts following command-line options (switches).
Basically they are quite similar to those of Perl.
.TP   
.B -0\fIdigit
specifies the input record separator (\fB$/\fR) as an octal number.
If no digits given, the null character is the separator. Other
switches may follow the digits. \fB-00\fR turns ruby into paragraph
mode. \fB-0777\fR makes ruby read whole file at once as a single
string, since there is no legal character with that value.
.TP
.B -a
turns on auto-split mode when used with \fB-n\fR or \fB-p\fR. In auto-split
mode, ruby executes
.nf
.ne 1
\&    $F = $_.split 
at beginning of each loop.
.fi
.TP
.B  -c
causes ruby to check the syntax of the script and exit without
executing. If there is no syntax error, ruby will print "Syntax
OK" to the standard output.
.TP
.B -K\fIc
specifies KANJI (Japanese character) code-set.
.TP
.B
-d --debug
turns on debug mode. \fB$DEBUG\fR will set TRUE.
.TP
.B -e \fIscript
specifies script from command-line. if \fB-e\fR switch specified,
ruby will not look for a script filename in the arguments.
.TP
.B -F \fIregexp
specifies input field separator (\fB$;\fR).
.TP
.B -i \fIextension
specifies in-place-edit mode. The extension, if specified, is
added to old filename to make a backup copy.
example:
.nf
.ne 8
\&    % echo matz > /tmp/junk
\&    % cat /tmp/junk
\&    matz
\&    % ruby -p -i.bak -e '$_.upcase!' /tmp/junk
\&    % cat /tmp/junk
\&    MATZ
\&    % cat /tmp/junk.bak
\&    matz
.fi
.TP
.B -I \fIdirectory
used to tell ruby where to load the library scripts. Directory
path will be added to the load-path variable (\fB$:\fR).
.TP
.B -l
enables automatic line-ending processing, which means firstly
set \fB$\\\fR to the value of \fB$/\fR, and secondly chops every line read
using \fBchop!\fR.
.TP
.B -n
causes ruby to assume the following loop around your script,
which makes it iterate over filename arguments somewhat like
sed \fB-n\fR or awk.
.nf
.ne 3          
\&    while gets
\&      ...
\&    end
.fi
.TP
.B -p
acts mostly same as \fB-n\fR switch, but print the value of variable
\fB$_\fR at the each end of the loop.
example:
.nf
.ne 2
\&    % echo matz | ruby -p -e '$_.tr! "a-z", "A-Z"'
\&    MATZ
.fi
.TP
.B -r \fIfilename
causes ruby to load the file using require. It is useful
with switches -n or \fB-p\fR.
.TP
.B -s
enables some switch parsing for switches after script name but
before any filename arguments (or before a \fB--\fR). Any switches
found there is removed from ARGV and set the corresponding
variable in the script.
example:
.nf
.ne 3          
\&    #! /usr/local/bin/ruby -s
\&    # prints "true" if invoked with `-xyz' switch.
\&    print "true\en" if $xyz
.fi
.TP
.B -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 \fB#!\fR on machines that don't support it, in the following
manner:
.nf
.ne 2          
\&    #! /usr/local/bin/ruby
\&    # This line makes the next one a comment in ruby \\
\&      exec /usr/local/bin/ruby -S $0 $*
.fi
On some systems $0 does not always contain the full pathname,
so you need \fB-S\fR switch to tell ruby to search for the script if
necessary.
To handle embedded spaces or such, A better construct than \fB$*\fR
would be \fB${1+"$@"}\fR, but it does not work if the script is being
interpreted by csh.
.TP
.B -v --verbose
enables verbose mode. Ruby will prints its version at the
beginning, and set the variable \fB$VERBOSE\fR to TRUE. Some
methods prints extra messages if this variable is TRUE. If this
switch is given, and no other arguments present, ruby quits
after printing its version.
.TP
.B --version
prints the version of ruby executable.
.TP
.B -w
enables verbose mode without printing version message at the
beginning. It set the variable \fB$VERBOSE\fR to TRUE.
.TP
.B -x\fR[\fIdirectory\fR]
tells ruby that the script is embedded in a message. Leading
garbage will be discarded until the first that starts with "\fB#!\fR"
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.
.TP
.B -X \fIdirectory
causes ruby to switch to the directory.
.TP
.B -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.
.PP
.SH AUTHOR
 Ruby is designed and implemented by Yukihiro Matsumoto <matz@netlab.co.jp>.