ruby.1

.\"Ruby is copyrighted by Yukihiro Matsumoto <matz@netlab.jp>.
.Dd December 31, 2002
.Dt RUBY(1) "" "Ruby Programmers Reference Guide"
.\".Dt RUBY 1
.Os UNIX
.Sh NAME
.Nm ruby
.Nd Interpreted object-oriented scripting language
.Sh SYNOPSIS
.Nm
.Op Fl -copyright
.Op Fl -version
.Op Fl Sacdlnpswvy
.Op Fl 0 Ns Op Ar octal
.Op Fl C Ar directory
.Op Fl F Ar pattern
.Op Fl I Ar directory
.Op Fl K Ar c
.Op Fl T Ns Op Ar level
.Op Fl e Ar command
.Op Fl i Ns Op Ar extension
.Op Fl r Ar library
.Op Fl x Ns Op Ar directory
.Op Fl -
.Op Ar program_file
.Op Ar argument ...
.Sh DESCRIPTION
Ruby is an 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 your
choice.
.Sh FEATURES
Ruby's features are as follows:
.Bl -tag -width 6n
.It Sy "Interpretive"
Ruby is an interpreted language, so you don't have to recompile
programs written in Ruby to execute them.
.Pp
.It Sy "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 a weaker compile
time check.
.Pp
.It Sy "No declaration needed"
You can use variables in your Ruby programs without any declarations.
Variable names denote their scope, local, global, instance, etc.
.Pp
.It Sy "Simple syntax"
Ruby has a simple syntax influenced slightly from Eiffel.
.Pp
.It Sy "No user-level memory management"
Ruby has automatic memory management.  Objects no longer referenced
from anywhere are automatically collected by the garbage collector
built into the interpreter.
.Pp
.It Sy "Everything is an object"
Ruby is the purely object-oriented language, and was so since its
creation.  Even such basic data as integers are seen as objects.
.Pp
.It Sy "Class, inheritance, and methods"
Of course, as an object-oriented language, Ruby has such basic
features like classes, inheritance, and methods.
.Pp
.It Sy "Singleton methods"
Ruby has the ability to define methods for certain objects.  For
example, you can define a press-button action for certain widget 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.
.Pp
.It Sy "Mix-in by modules"
Ruby intentionally does not have the multiple inheritance as it is a
source of confusion.  Instead, Ruby has the ability to share
implementations across the inheritance tree.  This is often called
.Sq Mix-in .
.Pp
.It Sy "Iterators"
Ruby has iterators for loop abstraction.
.Pp
.It Sy "Closures"
In Ruby, you can objectify the procedure.
.Pp
.It Sy "Text processing and regular expression"
Ruby has a bunch of text processing features like in Perl.
.Pp
.It Sy "Bignums"
With built-in bignums, you can for example calculate factorial(400).
.Pp
.It Sy "Exception handling"
As in Java(tm).
.Pp
.It Sy "Direct access to the OS"
Ruby can use most
.Ux
system calls, often used in system programming.
.Pp
.It Sy "Dynamic loading"
On most
.Ux
systems, you can load object files into the Ruby interpreter
on-the-fly.
.El
.Pp
.Sh OPTIONS
Ruby interpreter accepts following command-line options (switches).
They are quite similar to those of
.Xr perl 1 .
.Bl -tag -width "1234567890123" -compact
.Pp
.It Fl -copyright
Prints the copyright notice.
.Pp
.It Fl -version
Prints the version of Ruby interpreter.
.Pp
.It Fl 0 Ns Op Ar octal
(The digit
.Dq zero . )
Specifies the input record separator
.Pf ( Li "$/" )
as an octal number. If no digit is given, the null character is taken
as the separator.  Other switches may follow the digits.
.Fl 00
turns Ruby into paragraph mode.
.Fl 0777
makes Ruby read whole file at once as a single string since there is
no legal character with that value.
.Pp
.It Fl C Ar directory
Causes Ruby to switch to the directory.
.Pp
.It Fl F Ar pattern
Specifies input field separator
.Pf ( Li "$;" ) .
.Pp
.It Fl I Ar directory
Used to tell Ruby where to load the library scripts.  Directory path
will be added to the load-path variable
.Pf ( Li "$:" ) .
.Pp
.It Fl K Ar kcode
Specifies KANJI (Japanese) encoding.
.Pp
.It Fl S
Makes Ruby use the
.Ev PATH
environment variable to search for script, unless if its name begins
with a slash.  This is used to emulate
.Li #!
on machines that don't support it, in the following manner:
.Bd -literal -offset indent
#! /usr/local/bin/ruby
# This line makes the next one a comment in Ruby \e
  exec /usr/local/bin/ruby -S $0 $*
.Ed
.Pp
.It Fl T Ns Op Ar level
Turns on taint checks at the specified level (default 1).
.Pp
.It Fl a
Turns on auto-split mode when used with
.Fl n
or
.Fl p .
In auto-split mode, Ruby executes
.Dl $F = $_.split
at beginning of each loop.
.Pp
.It Fl c
Causes Ruby to check the syntax of the script and exit without
executing. If there are no syntax errors, Ruby will print
.Dq Syntax OK
to the standard output.
.Pp
.It Fl d
.It Fl -debug
Turns on debug mode.
.Li "$DEBUG"
will be set to true.
.Pp
.It Fl e Ar command
Specifies script from command-line while telling Ruby not to search
the rest of arguments for a script file name.
.Pp
.It Fl h
.It Fl -help
Prints a summary of the options.
.Pp
.It Fl i Ar extension
Specifies in-place-edit mode.  The extension, if specified, is added
to old file name to make a backup copy.  For example:
.Bd -literal -offset indent
% echo matz > /tmp/junk
% cat /tmp/junk
matz
% ruby -p -i.bak -e '$_.upcase!' /tmp/junk
% cat /tmp/junk
MATZ
% cat /tmp/junk.bak
matz
.Ed
.Pp
.It Fl l
(The lowercase letter
.Dq ell . )
Enables automatic line-ending processing, which means to firstly set
.Li "$\e"
to the value of
.Li "$/" ,
and secondly chops every line read using
.Li chop! .
.Pp
.It Fl n
Causes Ruby to assume the following loop around your script, which
makes it iterate over file name arguments somewhat like
.Nm sed
.Fl n
or
.Nm awk .
.Bd -literal -offset indent
while gets
  ...
end
.Ed
.Pp
.It Fl p
Acts mostly same as -n switch, but print the value of variable
.Li "$_"
at the each end of the loop.  For example:
.Bd -literal -offset indent
% echo matz | ruby -p -e '$_.tr! "a-z", "A-Z"'
MATZ
.Ed
.Pp
.It Fl r Ar library
Causes Ruby to load the library using require.  It is useful when using
.Fl n
or
.Fl p .
.Pp
.It Fl s
Enables some switch parsing for switches after script name but before
any file name arguments (or before a
.Fl - ) .
Any switches found there are removed from
.Li ARGV
and set the corresponding variable in the script.  For example:
.Bd -literal -offset indent
#! /usr/local/bin/ruby -s
# prints "true" if invoked with `-xyz' switch.
print "true\en" if $xyz
.Ed
.Pp
On some systems
.Li "$0"
does not always contain the full pathname, so you need the
.Fl S
switch to tell Ruby to search for the script if necessary.  To handle
embedded spaces or such.  A better construct than
.Li "$*"
would be
.Li ${1+"$@"} ,
but it does not work if the script is being interpreted by
.Xr csh 1 .
.Pp
.It Fl v
.It Fl -verbose
Enables verbose mode.  Ruby will print its version at the beginning,
and set the variable
.Li "$VERBOSE"
to true.  Some methods print extra messages if this variable is true.
If this switch is given, and no other switches are present, Ruby quits
after printing its version.
.Pp
.It Fl w
Enables verbose mode without printing version message at the
beginning.  It sets the
.Li "$VERBOSE"
variable to true.
.Pp
.It Fl x Ns Op Ar directory
Tells Ruby that the script is embedded in a message.  Leading garbage
will be discarded until the first that starts with
.Dq #!
and contains the string,
.Dq ruby .
Any meaningful switches on that line will applied.  The end of script
must be specified with either
.Li EOF ,
.Li "^D" ( Li "control-D" ) ,
.Li "^Z" ( Li "control-Z" ) ,
or reserved word
.Li __END__ .
If the directory name is specified, Ruby will switch to that directory
before executing script.
.Pp
.It Fl y
.It Fl -yydebug
Turns on compiler debug mode.  Ruby will print a 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.
.El
.Pp
.Sh ENVIRONMENT
.Bl -tag -width "RUBYLIB_PREFIX" -compact
.It Ev RUBYLIB
A colon-separated list of directories that are appended to Ruby's
library load path
.Pf ( Li "$:" ) .
.Pp
e.g.:
.Dl RUBYLIB="$HOME/lib/ruby:$HOME/lib/rubyext"
.Pp
.It Ev RUBYOPT
Additional Ruby options.
.Pp
e.g.
.Dl RUBYOPT="-w -Ke"
.Pp
.It Ev RUBYPATH
A colon-separated list of directories that Ruby searches for
Ruby programs when the
.Fl S
flag is specified.  This variable precedes the
.Ev PATH
environment variable.
.Pp
.It Ev RUBYSHELL
The path to the system shell command.  This environment variable is
enabled for only mswin32, mingw32, and OS/2 platforms.  If this
variable is not defined, Ruby refers to
.Ev COMSPEC .
.Pp
.It Ev PATH
Ruby refers to the
.Ev PATH
environment variable on calling Kernel#system.
.Pp
.It Ev RUBYLIB_PREFIX
This variable is obsolete.
.El
.Pp
.Sh AUTHORS
Ruby is designed and implemented by
.An Yukihiro Matsumoto Aq matz@netlab.jp .