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ruby [options] [--] [programfile] [arguments] |
--''
(two hyphens).
If no filename is present on the command line, or if the filename is
a single hyphen (-), Ruby reads the program source from standard
input.
Arguments for the program itself follow the program name. For example:
% ruby -w - "Hello World"
will enable warnings, read a program from standard input, and pass it
the quoted string "Hello World" as an argument.
-00 indicates
paragraph mode: records are separated by two successive default
record separator characters. -0777 reads the entire file at once (as it
is an illegal character). Sets $/.
-n or -p;
equivalent to executing
{$F at the top of each loop iteration.
--copyright$DEBUG to true.
This can be used by your programs to
enable additional tracing.
-e's
are allowed, and the commands are treated as multiple lines in the
same program. If programfile is omitted when -e is
present, execution stops after the -e commands have been run.
$;) used as the default for
split() (affects -a).
$LOAD_PATH
($:). Multiple -I options may be present, and
multiple directories may appear following each -I. Directories
are separated by a ``:'' on Unix-like systems and by a ``;'' on
DOS/Windows systems.
ARGV files in place.
For each
file named in ARGV, anything you write to standard output will
be saved back as the contents of that file.
A backup copy of the file will be made if
extension is supplied.
% ruby -pi.bak -e "gsub(/Perl/, 'Ruby')" *.txt
$\ to the value of $/ and chops every input line
automatically.
while gets; ...; end'' loop around your program.
For example, a simple grep command might be implemented as:
% ruby -n -e "print if /wombat/" *.txt
while gets; ...; print; end.''
% ruby -p -e "$_.downcase!" *.txt
requires the named library before executing.
RUBYPATH
or PATH environment
variable.
--, are removed
from ARGV and set to a global variable named for the switch. In
the following example, the effect of this would be to set the variable
$opt to ``electric''.
% ruby -s prog -opt=electric ./mydata
$SAFE.
--version-v, reads program from
standard input if no program files are present on the command line.
We recommend running your Ruby programs with -w.
-C directory.
#!ruby line and changes working
directory to directory if given.
ARGV.
For instance, invoking Ruby as
% ruby -w ptest "Hello World" a1 1.6180
yields an ARGV array containing ["Hello World", a1,
1.6180]. There's a gotcha here for all you C
programmers---ARGV[0] is the first argument to the program, not
the program name.
The name of the current program is
available in the global variable $0.
Kernel#exit terminates your program, returning a
status value to the operating system. However, unlike some languages,
exit doesn't just terminate the program immediately.
Kernel#exit first raises a
SystemExit exception, which you may catch, and then performs a
number of cleanup actions, including running any registered
at_exit methods and object finalizers. See the reference for
Kernel#exit beginning on page 419 for details.
ENV. It responds to the same
methods as Hash.[ENV is not actually a hash, but
if you need to, you can convert it into a Hash using
ENV#to_hash.]
The values of some environment variables are read by Ruby
when it first starts. These variables modify the behavior of the interpreter,
as shown in Table 13.1 on page 141.
Environment variables used by Ruby
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ENV object, which on most systems
changes the values of the corresponding environment variables. However,
this change is local to the process that makes it and to any
subsequently spawned child processes.
This inheritance of environment variables is illustrated in the code
that follows. A subprocess changes an environment variable and this
change is seen in a process that it then starts. However, the change
is not visible to the original parent. (This just goes to prove that
parents never really know what their children are doing.)
puts "In parent, term = #{ENV['TERM']}"
fork do
puts "Start of child 1, term = #{ENV['TERM']}"
ENV['TERM'] = "ansi"
fork do
puts "Start of child 2, term = #{ENV['TERM']}"
end
Process.wait
puts "End of child 1, term = #{ENV['TERM']}"
end
Process.wait
puts "Back in parent, term = #{ENV['TERM']}"
|
In parent, term = xterm Start of child 1, term = xterm Start of child 2, term = ansi End of child 1, term = ansi Back in parent, term = xterm |
require or load to bring a library module into your
Ruby program. Some of these modules are supplied with Ruby, some you
installed off the Ruby Application Archive, and some you wrote
yourself. How does Ruby find them?
When Ruby is built for your particular machine, it predefines a set
of standard directories to hold library stuff. Where these are
depends on the machine in question. You can
determine this from the command line with something like:
% ruby -e 'puts $:' |
/usr/local/lib/ruby/site_ruby/1.6/i686-linux /usr/local/lib/ruby/site_ruby/1.6 /usr/local/lib/ruby/site_ruby /usr/local/lib/ruby/1.6/i686-linux /usr/local/lib/ruby/1.6 . |
site_ruby directories are intended to hold modules and extensions that
you've added.
The architecture-dependent directories (i686-linux
in this case) hold executables and other things specific to this
particular machine. All these directories are automatically included
in Ruby's search for modules.
Sometimes this isn't enough. Perhaps you're working on a large project
written in Ruby, and you and your colleagues have built a substantial
library of Ruby code. You want everyone on the team to have access to
all of this code. You have a couple of options to accomplish this. If
your program runs at a safe level of zero (see
Chapter 20 beginning on page 257),
you can set the environment variable
RUBYLIB to a list of one or more directories to be
searched.[The separator between entries depends on your
platform. For Windows, it's a semicolon; for Unix, a colon.] If your
program is not setuid,
you can use the command-line parameter -I
to do the same thing.
Finally,
the Ruby variable $: is an array of places to search
for loaded files. This variable is initialized to the list of standard
directories, plus any additional ones you specified using RUBYLIB
and -I. You can always add additional directories to this array
from within your running program.
Config within the
library file ``rbconfig.rb''.
After installation, any Ruby program can use this module to get
details on how Ruby was compiled.
require "rbconfig.rb" |
||
include Config |
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CONFIG["host"] |
» | "i686-pc-linux" |
CONFIG["LDFLAGS"] |
» | "-rdynamic" |
mkmf beginning on page 455 for details.
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