ruby
Interpreted object-oriented scripting language
Synopsis
ruby
[--copyright] [--version]
[-Sacdlnpswvy] [-0[octal]]
[-C directory]
[-F pattern]
[-I directory]
[-K c]
[-T[level]]
[-e command]
[-i[extension]]
[-r library]
[-x[directory]] [--]
[program_file] [argument ...]
add an example, a script, a trick and tips
examples
source
Ruby shell instead of Bash shell in Ubuntu?
You wouldn't want to do that. It would mean, for example, putting
all arguments passed on to programs in double quotes. (ipython,
which resembles ruby's irb, can do something like this, but it's
cumbersome) Although I agree that bash and co are not great, they
can't just be replaced, as an interactive prompt at least, by a
general-purpose programming language.
source
How to configure installed Ruby and gems?
I'm sorry if I've misunderstood the question but can you not just
do:
export GEM_PATH=/home/myown
Maybe put it in your .bashrc.
source
When to use Bash and when to use Perl/Python/Ruby?
Bash is a Unix shell it includes a scripting language. It is
rather command processor. you control the way how you run
commands, you actually run them.
Perl/Ruby/Python are general purpose languages.
When you want a shell script, you use Bash
If you want more complex task or not related to shell. Use Python
etc.
I would never compare these languages actually. Python etc. are
portable. You can run them anywhere. Bash is for Unix only.
Python etc. have tons of reusable libraries solving millions of
tasks.
It's almost the same if you ask. "When to use Paint and when to
use Photoshop"
For processing emails I would use Ruby, again, because it has a
lot of reusable libraries.
But the best way would be combine bash and ruby.
That would be right. Like you create a email lrocessor in ruby
and bash script would invoke that ruby script and run other
commans ds.
So whenever you need command processor you use bash. You run unix
commands and control them.
source
java wont run under chroot cause it can not find shared libraries
seems you did not mount proc
under your chroot.
try to mount its own proc
by:
# inside chroot
mount -t proc none /proc
or to "share" system's proc by:
# outside chroot
mount -o bind /proc /path/to/chroot/proc
source
Linux: how to uninstall something that isn't a package...?
Check the makefile for a 'make uninstall' target. Sometimes they
come with those.
Failing that, the best you can do is carefully read the 'make
install' target and then manually undo what it did.
source
Single GUI Application raspberrypi
I'd look into the inittab file. You edit it to configure what runs
on bootup. Check the /etc/inittab on the distro that you use to
see what is currently set up to run on your distro.
You could always run it from /etc/init.d/ and /etc/rc*.d/
One advantage to inittab is you can configure it to respawn if it
crashes.
If I were you I'd migrate this to a more topic specific
stackexchange site. Both UNIX/Linux and RaspberryPi specific
forums exist.
source
How do I ensure a process is running, even if it kills itself? (it needs to be restarted then)
I cross-posted my question to stackoverflow.com, where I got the
answer ;)
http://stackoverflow.com/a/13627784/1081936
Restarting a application is a bad workaround, not a solution.
i recommend to review the documentation of your bot, look for a
option to configure after how many bad retries it exits or how
to disable this functionality completely. if the bot is open
source, you can also review its source code and modify the
retry code. Try to find a clean solution.
if you really want to restart it, i would create a shellscript
that runs the bot in a loop. make sure bot.rb does not fork
into the background:
#/bin/bash
for (( ; ; ))
do
./bot.rb
done
you can run that script with nohup ./startscript.sh
&
so it does not terminate if you close the console.
source
Mainstream Linux on 1GB HDD
There are plenty choices over on pendrivelinux.
I wouldn't be to worried about choosing a mainstream
linux. Most linuxes are more alike then they are different,
so if you learn the basics on debian/suse you can be pretty sure
you can get around in ubuntu.
source
Define extra `$PATH` for either Passenger or nginx
The ruby options are a good way to do this. Specify that the
$LOAD_PATH have /usr/bin.
-Idirectory specify $LOAD_PATH directory (may be used more than once)
It is what it is there for, after all.
Another thing you can do is push the directory onto the $: global
psuedo-variable.
$:.push("/usr/bin")
This would fit wherever you have your environment customization
in your application.
I would probably do this for the Rails Application itself, as
that is where you are concerned about it. It is what you have
control over.
source
Ruby/gem installation paths scattered all over, cause?
I installed rvm, I still don't know why there was such a mess but
now I can just force a certain ruby version easily, and I know
where all the gems get installed into. (into the rvm directory)
Works for me.
description
Ruby is an interpreted scripting
language for quick and easy object-oriented programming. It
has many features to process text files and to do system
management tasks (as in Perl). It is simple,
straight-forward, and extensible.
If you want a
language for easy object-oriented programming, or you
don’t like the Perl ugliness, or you do like the
concept of LISP, but don’t like too much parentheses,
Ruby may be the language of your choice.
options
Ruby interpreter accepts
following command-line options (switches). They are quite
similar to those of perl(1).
--copyright
Prints the
copyright notice.
--version
Prints the
version of Ruby interpreter.
-0[octal]
(The digit
’’zero’’.) Specifies the input
record separator ($/) as an octal number. If no digit is
given, the null character is taken as 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.
-C
directory
Causes Ruby to
switch to the directory.
-F
pattern
Specifies input
field separator ($;).
-I
directory
Used to tell
Ruby where to load the library scripts. Directory path will
be added to the load-path variable ($:).
-K kcode
Specifies KANJI
(Japanese) encoding.
-S
Makes Ruby use
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 $*
-T[level]
Turns on taint
checks at the specified level (default 1).
-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 are no syntax errors, Ruby will print
’’Syntax OK’’ to the standard
output.
-d
--debug
Turns on debug
mode. $DEBUG will be set to true.
-e
command
Specifies
script from command-line while telling Ruby not to search
the rest of arguments for a script file name.
-h
--help
Prints a
summary of the options.
-i
extension
Specifies
in-place-edit mode. The extension, if specified, is added to
old file name to make a backup copy. For example:
% echo matz
> /tmp/junk
% cat /tmp/junk
matz
% ruby -p -i.bak -e ’$_.upcase!’ /tmp/junk
% cat /tmp/junk
MATZ
% cat /tmp/junk.bak
matz
-l
(The lowercase
letter ’’ell’’.) Enables automatic
line-ending processing, which means to 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 file name arguments somewhat like sed
-n or awk.
while gets
...
end
-p
Acts mostly
same as -n switch, but print the value of variable $_ at the
each end of the loop. For example:
% echo matz |
ruby -p -e ’$_.tr! "a-z",
"A-Z"’
MATZ
-r
library
Causes Ruby to
load the library using require. It is useful when using
-n or -p.
-s
Enables some
switch parsing for switches after script name but before any
file name arguments (or before a --). Any
switches found there are removed from ARGV and set the
corresponding variable in the script. For example:
#!
/usr/local/bin/ruby -s
# prints "true" if invoked with ’-xyz’
switch.
print "true\n" if $xyz
On some systems
$0 does not always contain the full pathname, so you need
the -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(1).
-v
--verbose
Enables verbose
mode. Ruby will print its version at the beginning, and set
the variable $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.
-w
Enables verbose
mode without printing version message at the beginning. It
sets the $VERBOSE variable 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 the 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.
-y
--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.
class- inheritance- and
methods
Of course, as an object-oriented language, Ruby has such basic
features like classes, inheritance, and methods.
direct access to the
OS
Ruby can use most UNIX system calls, often used in system
programming.
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.
features
Ruby’s features are as follows:
Interpretive
Ruby is an interpreted language, so you don’t have to recompile
programs written in Ruby to execute them.
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.
No declaration needed
You can use variables in your Ruby programs without any
declarations. Variable names denote their scope, local, global,
instance, etc.
Simple syntax
Ruby has a 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 into the interpreter.
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.
Class, inheritance, and methods
Of course, as an object-oriented language, Ruby has such basic
features like classes, inheritance, and methods.
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.
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
’Mix-in’.
Iterators
Ruby has iterators for loop abstraction.
Closures
In Ruby, you can objectify the procedure.
Text processing and regular expression
Ruby has a bunch of text processing features like in Perl.
Bignums
With built-in bignums, you can for example calculate
factorial(400).
Exception handling
As in Java(tm).
Direct access to the OS
Ruby can use most UNIX system calls, often used in system
programming.
Dynamic loading
On most UNIX systems, you can load object files into the Ruby
interpreter on-the-fly.
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.
text processing and regular
expression
Ruby has a bunch of text processing features like in Perl.
v br
--verbose
Enables verbose mode. Ruby will print its version at the
beginning, and set the variable $VERBOSE to true. Some methods
print extra messages if this variable is true. If this switch is
given, and no other switches are present, Ruby quits after
printing its version.
authors
RUBYLIB
A
colon-separated list of directories that are added to
Ruby’s library load path ($:). Directories from this
environment variable are searched before the standard load
path is searched.
e.g.:
RUBYLIB="$HOME/lib/ruby:$HOME/lib/rubyext"
RUBYOPT
Additional Ruby
options.
e.g.
RUBYOPT="-w -Ke"
RUBYPATH
A
colon-separated list of directories that Ruby searches for
Ruby programs when the -S flag is specified.
This variable precedes the PATH environment variable.
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 COMSPEC.
PATH
Ruby refers to
the PATH environment variable on calling Kernel#system.
RUBYLIB_PREFIX
This variable
is obsolete.
Ruby is designed and implemented
by Yukihiro Matsumoto <matz[:at:]netlab[:dot:]jp>.
UNIX
December 31, 2002 UNIX