Friday afternoon, I finally got tired of a bug in "Open Terminal Here", a Bash script I was using so far. I made a Python replacement...

Open Terminal Here ?

"Open Terminal Here" just a simple Bash script meant to be launched from a right-click within a directory opened in Nautilus, the Gnome file manager. As the name states, the gnome-terminal should be launched with its working directory being set to the currently opened directory. Simply handy! Only one problem: setting the  working directory was failing whenever the name of directory contained non-ASCII characters. 🙁

This "Open Terminal Here" is not a standard functionality of Nautilus (as opposed to Dolphin where you can just press Maj+F4 to launch a "konsole"). Rather, you have to download an extension script from G-Scripts, a nice central repository, and drop it in a quite buried directory (~/.gnome2/nautilus-scripts). When it comes to the "Open Terminal Here" function, there are several scripts available. Choosing between these is up to the visitor...

"Open Terminal Here" in Bash

Here is the central part of the Bash script I was using so far:

base="`echo $NAUTILUS_SCRIPT_CURRENT_URI | cut -d'/' -f3- | sed 's/%20/ /g'`"
if [ -z "$NAUTILUS_SCRIPT_SELECTED_FILE_PATHS" ]; then
     dir="$base"
else 
     while [ ! -z "$1" -a ! -d "$base/$1" ]; do shift; done
     dir="$base/$1"
fi

gnome-terminal --working-directory="$dir"

I had never paid attention to this code until Friday (especially since I have such a poor Bash understanding). I now realize that line 1 does most of the job, which is :

1. retreive the $NAUTILUS_SCRIPT_CURRENT_URI environment variable.
2. cut the "file://" prefix from the URI
3. replace "%20" by real space characters " "

This Bash script works most of the time, except with directory names containing non-ASCII characters. Indeed, in a directory called "études notes" for example, Nautilus sets the URI variable to "file:///home/pierre/%C3%A9tudes%20notes". One can see how "é" gets encoded as "%C3%A9" and the Bash script doesn't perform any decoding.

Now "Open Terminal Here" with Python

In order to support non-ASCII, I tried to build my own script. I chose Python simply because that's the language I'm the most familiar with. The entire source is a GitHub Gist. Here are the main lines:

import os
from urllib import unquote
from subprocess import Popen

# 1a) Retrieve the URI of the current directory:
env = os.getenv("NAUTILUS_SCRIPT_CURRENT_URI", "/home/pierre")

# 1b) Process the URI to make it just a regular Path string
env = env.replace('file://', '') # Should fail with Python 3 ?!
env = unquote(env) # decode the URI

# 2) Launch gnome-terminal:
Popen(["gnome-terminal", '--working-directory=%s' % env])

Well, it's basically the same as in Bash, except with a useful call to the urllib.unquote function which performs all the URI decoding job. All imports are from the Python standard library: great !

And by the way, with Perl !

While writing this post, I realized I had on my laptop a second "Open Terminal Here" script. I had forgotten about it because it was disabled for I don't know what reason. It's a Perl script, also coming from G-Script. Here are the main lines:

use strict;

$_ = $ENV{'NAUTILUS_SCRIPT_CURRENT_URI'};
if ($_ and m#^file:///#) {
  s/%([0-9A-Fa-f]{2})/chr(hex($1))/eg;
  s#^file://##;
  exec "gnome-terminal --working-directory='$_'";
}

What can be said except that it also works ! The URI decoding is nicely performed by "chr(hex($1))". I actually think the author wrote this script for the very same reason I wrote a Python one: "he loves Perl!" 😉

Conclusion ?

I don't know if it's that useful to have three versions of a script to solve the very same tiny problem... Still, one can notice the vivid differences in the programming approach: while my Python scripts relies mostly function coming from standard modules, the Perl script is literally built on Regular Expressions. No surprise !

Finally, the Bash script just calls command line utilities (cut and sed), but doesn't decode the URI. Is there a command line program for that ?

And what about Haskell ?

I'll keep this for another day 😉 I need to get a Fistful of Monads first. Would be a nice experiment though...