Tag Archives: Ruby

rbenv and multiple local ruby version installs (like perlbrew)

When I was using perl as my primary development language, I had a platform of tools in place to make my perl development fun and productive. This included tools like Perl::Dancer, DBIx::Class, cpanm, and perlbrew. Perlbrew was a tool I used to maintain multiple versions of perl in my local development environment, so that I could test my code against multiple perl and module versions to ensure that it worked on the largest range of platforms ( and to avoid dependency related bugs ).

This allowed me to run my code against Perl 5.10, 5.12, and 5.14, and so on each with their own module-base, fully isolated from each-other.

Now I’m working with many different tools these days, and haven’t had the opportunity to work with other languages to the extent that I’ve worked with Perl, but I have been playing with Ruby and Golang. Using Ruby, I immediately thought that I would like to play with multiple versions of Ruby without altering the ‘system’ ruby on my workstation. A quick search of ‘perlbrew for ruby’ lead me to rbenv which seems to be exactly what I was looking for.

Some examples of how rbenv works:

# list all available versions:
$ rbenv install -l
# install a Ruby version:
$ rbenv install 2.0.0-p247
# Sets a local application-specific Ruby version by writing the version name to a .ruby-version file in the current directory.
$ rbenv local 1.9.3-p327
# Sets the global version of Ruby to be used in all shells by writing the version name to the ~/.rbenv/version file.
$ rbenv global 1.8.7-p352
# Sets a shell-specific Ruby version by setting the RBENV_VERSION environment variable in your shell
$ rbenv shell jruby-1.7.1
# Lists all Ruby versions known to rbenv, and shows an asterisk next to the currently active version.
$ rbenv versions 1.8.7-p352 1.9.2-p290 * 1.9.3-p327 (set by /Users/sam/.rbenv/version) jruby-1.7.1 rbx-1.2.4 ree-1.8.7-2011.03
# Displays the currently active Ruby version, along with information on how it was set.
$ rbenv version 1.9.3-p327 (set by /Users/sam/.rbenv/version)
# Displays the full path to the executable that rbenv will invoke when you run the given command.
$ rbenv which irb

Examples of recursion, in Perl, Ruby, and Bash

This article is in response to the following question posted in the Perl community group on  LinkedIn:

I’m new to PERL and trying to understand recursive subroutines. Can someone please explain with an example (other than the factorial ;) ) step by step, how it works? Thanks in Advance.

Below, are some very simplified code examples in Perl, Ruby, and Bash.

A listing of the files used in these examples:

blopez@blopez-K56CM ~/hello_scripts 
$ tree .
 ├── hello.pl
 ├── hello.rb
 └── hello.sh
0 directories, 3 files
blopez@blopez-K56CM ~/hello_scripts $

Recursion example using Perl:

– How the Perl script is executed, and it’s output:

blopez@blopez-K56CM ~/hello_scripts $ perl hello.pl "How's it going!"
How's it going!
How's it going!
How's it going!
blopez@blopez-K56CM ~/hello_scripts $

– The Perl recursion code:

#!/usr/bin/env perl
use Modern::Perl;
my $status_update = $ARGV[0]; # get script argument
sub hello_world
    my $status_update = shift; # get function argument
    say "$status_update";
    sleep 1; # sleep, or eventually crash your system
    &hello_world( $status_update ); # execute myself with argument
&hello_world( $status_update ); # execute function with argument

Recursion example using Ruby:

– How the Ruby script is executed:

blopez@blopez-K56CM ~/hello_scripts 
$ ruby hello.rb "Doing great!"
Doing great!
Doing great!
Doing great!
^Chello.rb:7:in `sleep': Interrupt
    from hello.rb:7:in `hello_world'
    from hello.rb:8:in `hello_world'
    from hello.rb:8:in `hello_world'
    from hello.rb:11:in `'
blopez@blopez-K56CM ~/hello_scripts $

Note: In Ruby’s case, stopping the script with CTRL-C returns a bit more debugging information.

– The Ruby recursion code:

#!/usr/bin/env ruby
status = ARGV[0] # get script argument
def hello_world( status ) # define function, and get script argument
    puts status
    sleep 1 # sleep, or potentially crash your system
    return hello_world status # execute myself with argument
hello_world status # execute function with argument

Recursion example using Bash:

– How the Bash script is executed:

blopez@blopez-K56CM ~/hello_scripts $ bash hello.sh "..nice talking to you."
..nice talking to you.
..nice talking to you.
..nice talking to you.
blopez@blopez-K56CM ~/hello_scripts $

– The Bash recursion code:

#!/usr/bin/env bash
mystatus=$1 # get script argument
hello_world() {
    mystatus=$1 # get function argument
    echo "${mystatus}"
    sleep 1 # breath between executions, or crash your system
    hello_world "${mystatus}" # execute myself with argument
hello_world "${mystatus}" # execute function with argument