Tag Archives: Unix

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Ruby: interrupt a running script

Need to stop a running script in mid-stride and check/change variables?

Here’s how:

1. add Pry

require ‘pry’

2. add an Exception handler

rescue Exception => exception

    binding.pry

end

Now just use Ctrl C (on a Mac, Unix and Linux) and you’ll exit out with a debugger command prompt.

And exit pry permanently with:

!!!

    

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Rails: Phusion Passenger

Passenger is an application server for Ruby (Rack) and Python (WSGI) apps.

Some notes on installing it:

https://www.phusionpassenger.com/download

Ignore the docs that suggest:

$ sudo gem install passenger

$ sudo passenger-install-apache2-module

Instead use:

gem install passenger

passenger-install-apache2-module

Then paste the LoadModule code it spits out at the end into your Apache conf file.

Test whether Passenger has installed by running:

curl -sI localhost | grep ^Server

and check for the “Phusion_Passenger” signature. E.g. 

Server: Apache/2.2.22 (Unix) DAV/2 PHP/5.3.15 with Suhosin-Patch Phusion_Passenger/4.0.5 mod_ssl/2.2.22 OpenSSL/0.9.8x

If you need to uninstall Passenger using sudo then:

$ sudo gem uninstall passenger

And a discussion on whether to use rvmsudo or not here:

https://groups.google.com/forum/#!topic/rubyversionmanager/9dnmAsTiHR4

In short, https://www.phusionpassenger.com/download

suggests using sudo but the rvm page suggests not:

https://rvm.io/integration/passenger

Note:

If you get a warning doing the passenger install apache2 module like this:

rvmsudo rvm get stable && rvm reload && rvmsudo rvm repair all

Warning: can not check /etc/sudoers for secure_path, falling back to call via /usr/bin/env, this breaks rules from /etc/sudoers. Run:

    export rvmsudo_secure_path=1

Then run:

    export rvmsudo_secure_path=1

and:

rvmsudo rvm get stable && rvm reload && rvmsudo rvm repair all

(remember to run rvm requirements afterwards)

On the Mac the Apache conf and restart commands go like this:

[~]$ sudo vim /etc/apache2/httpd.conf

[~]$ sudo apachectl restart

See also:

https://developer.apple.com/library/mac/#featuredarticles/PhusionRails/_index.html

and this very useful guide:

http://jasoncodes.com/posts/mac-os-rails-server

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Rails: Phusion Passenger

Passenger is an application server for Ruby (Rack) and Python (WSGI) apps.

Some notes on installing it:

https://www.phusionpassenger.com/download

Ignore the docs that suggest:

$ sudo gem install passenger

$ sudo passenger-install-apache2-module

Instead use:

gem install passenger

should be sufficient and rvm.io suggests just running:

passenger-install-apache2-module

See also:

http://stackoverflow.com/questions/17245105/passenger-module-fails-to-install

and

http://stackoverflow.com/questions/17248660/installing-passenger-use-sudo-rvmsudo-or-nothing

Then, paste the LoadModule code it spits out at the end into your Apache conf file.

Test whether Passenger has installed by running:

curl -sI localhost | grep ^Server

and check for the “Phusion_Passenger” signature. E.g. 

Server: Apache/2.2.22 (Unix) DAV/2 PHP/5.3.15 with Suhosin-Patch Phusion_Passenger/4.0.5 mod_ssl/2.2.22 OpenSSL/0.9.8x

If you need to uninstall Passenger using sudo then:

$ sudo gem uninstall passenger

And a discussion on whether to use rvmsudo or not here:

https://groups.google.com/forum/#!topic/rubyversionmanager/9dnmAsTiHR4

In short, https://www.phusionpassenger.com/download

suggests using sudo but the rvm page suggests not:

https://rvm.io/integration/passenger

Note:

If you get a warning doing the passenger install apache2 module like this:

rvmsudo rvm get stable && rvm reload && rvmsudo rvm repair all

Warning: can not check /etc/sudoers for secure_path, falling back to call via /usr/bin/env, this breaks rules from /etc/sudoers. Run:

    export rvmsudo_secure_path=1

Then run:

    export rvmsudo_secure_path=1

and:

rvmsudo rvm get stable && rvm reload && rvmsudo rvm repair all

(remember to run rvm requirements afterwards)

On the Mac the Apache conf and restart commands go like this:

[~]$ sudo vim /etc/apache2/httpd.conf

[~]$ sudo apachectl restart

See also:

https://developer.apple.com/library/mac/#featuredarticles/PhusionRails/_index.html

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.bash_profile vs .bashrc

The difference between .bash_profile and .bashrc?

It’s always slightly confusing to remember how these work on Linux, Unix and Mac OS X. According to the bash man page, .bash_profile gets run for every login shell (i.e. when you login) – put lengthy, one-off stuff there like the daily news

.bashrc gets run for every non-login shell (e.g. when you open up another terminal in your window system)

Unfortunately Mac OS X does things slightly differently – .bash_profile gets called for each new instance of a Terminal!

More:

http://www.joshstaiger.org/archives/2005/07/bash_profile_vs.html

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Pry – Part 5 – Pry at runtime

Assuming you’ve halted the runtime at the point where you invoked the Pry REPL (see Pry – Part 4), you should have the Pry REPL.

A. The main ways of navigating the stack are the ls and cd commands.

ls shows you methods, constants and variables.

cd moves you into the new context (object or scope).

1. ls

2. cd

B. Apart from navigating state, there are two other commands that are very useful, show-method and show-doc.

1. show-method
This shows the source for a method or class.

2. show-doc shows the documentation by running the method comments through rdoc or yard

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Pry – Part 2

More on using Pry.

Let’s play around with it a little using the Hello World gem (if you haven’t already installed it, use: gem install hello_world). Then, in pry:

Some useful commands:

1. ls:
ls shows you which methods, constants and variables are accessible to Pry. By
default it shows you the local variables defined in the current shell, and any
public methods or instance variables defined on the current object.

So we can list, class methods:

i.e. nothing.

Instance methods:

i.e. this method is available.

And this is the default, i.e.

e.g.:

2. cd
cd moves you into a new context (object or scope). As in UNIX shells use cd .. to go
back, cd / to return to Pry top-level and cd – to toggle between last two
scopes.

So,

and now:

So, we can invoke it like this:

However, if we’re only interested in the output value and not the return value then we can use a semi-colon:

More in Pry – Part 3.

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Automatic Post Tagger

Not quite as awesome as an automatic post categoriser but still pretty handy:

http://wordpress.org/extend/plugins/automatic-post-tagger/