While I was meant to be working on my thesis, I decided to update my little script to grab images from the built in iSight camera. The older version depended upon a instance of procfs to be started from within a login shell (which is not always possible).

To get around this, I stared looking for a way to inject a process into a particular mach bootstrap session (After reading the OSX internals book, I knew this was where I should be looking). Now, I will not claim that this script is the best thing I have written… It requires you to set up a rule in the sudoers file to allow the _www user to execute the specified sudo command (as root). I will leave writing this line as an exercise to the user (I have written one version, it is just not completely secure). You will also have to grab the isightcapture binary from off the net, and update the script with the correct location.

#!/bin/bash

function pgrep {
    ps -A -o pid=,command= | grep "$1" | awk '{ print $1; }' | grep -v $$
}

function cleanup {
    if [ ! -z "$MYTEMP" ]; then
        rm -rf "$MYTEMP"
    fi
}

MYTEMP="$(mktemp -d)"
trap "cleanup" 15 0

LOGIN_WINDOW_PID="$(pgrep loginwindow.app)"
OUTPUT_FILENAME="${MYTEMP}/isightcapture.jpg"
sudo launchctl bsexec "${LOGIN_WINDOW_PID}" /Users/gregdarke/bin/isightcapture -t jpg "${OUTPUT_FILENAME}"

echo -en 'Content-type: image/jpeg\r\n\r\n'
cat "${OUTPUT_FILENAME}"

One thing that most programmers will cringe at, is the thought of placing a database into a version control repository such as subversion or mercurial. Now I know that many of have done this for various reasons (I know I am guilty of it myself).

The point of this post is to show how this can be made a little nicer under mercurial using encode/decode filters. With a carefully constructed set of filters, you are able to actually perform text diffs and make sane merges between repositories. All you have to do is drop the following into your hgrc file (either the one in your project or ~/.hgrc):

[encode]
data.db = tempfile: sqlite3 INFILE .dump > OUTFILE

[decode]
data.db = tempfile: sqlite3 OUTFILE '.read INFILE'

This requires that you have the sqlite3 binary installed, otherwise you will end up with a data.db file containing the raw sql used to generate the database.