How to load an ESRI Shapefile into a PostGIS DB

Assuming a shapefile called myshapefile.shp, a table mytable in schema xyz, in a PostGIS enabled database called mydb on localhost. The table is owned by user dbuser who has password “secret”.

Using shp2pgsql

shp2pgsql myshapefile -I xyz.mytable > statements.sql
psql -d mydb -h localhost -U dbuser -f statements.sql

This tip and many more can be read in Making Maps Fast.

Using ogr2ogr

This is even easier with ogr2ogr:

ogr2ogr -f "PostgreSQL" PG:"host=localhost user=dbuser dbname=mydb password=secret" -lco SCHEMA=xyz myshapefile.shp

Hello world plugin for Nagios in Python

Nagios looks at 1) return codes and 2) output to stdout. This is the hello world of Nagios plugins, written in Python:

check_helloworld.py:

#!/usr/bin/env python
 
# optparse is Python 2.3 - 2.6, deprecated in 2.7
# For 2.7+ use http://docs.python.org/library/argparse.html#module-argparse
from optparse import OptionParser
 
# CONSTANTS FOR RETURN CODES UNDERSTOOD BY NAGIOS
# Exit statuses recognized by Nagios
UNKNOWN = -1
OK = 0
WARNING = 1
CRITICAL = 2
 
# TEMPLATE FOR READING PARAMETERS FROM COMMANDLINE
parser = OptionParser()
parser.add_option("-m", "--message", dest="message", 
   default='Hello world', help="A message to print after OK - ")
(options, args) = parser.parse_args()
 
# RETURN OUTPUT TO NAGIOS
# USING THE EXAMPLE -m PARAMETER PARSED FROM COMMANDLINE
print 'OK - %s' % (options.message)
raise SystemExit, OK

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Saving output from ‘text to speech’ to a file on Mac OS X

In terminal you can write something like:

say 'hello world'

Which will make your computer talk. To save the audio output to a file, use the -o option. A full example is:

say -o hello.aiff -v 'Alex' 'Hello, my name is Alex'
open hello.aiff

This will say ‘Hello, my name is Alex’, in the voice of ‘Alex’ (other voice-options are ‘Bruce’, ‘Fred, ‘Kathy’, ‘Vicki’ and ‘Victoria’), and save the output to ‘hello.aiff’.

It seems there is no option for setting the speed (can be set in System preferences -> speech). See man say for all options. Interesting options include sending the output over the network.

Kill process from within top in Terminal on Mac OS X

My top seems to act a little strange (running Snow Leopard). It doesn’t respond to the key commands I’m used to, e.g. for sorting on Memory Usage etc. Nevertheless, this is how I found out (by chance really) how to kill a process from within top.

First start top using sudo:

sudo top

Press shift + s. This will promt for a signal. Enter the word ‘kill’ (if not already selected). Hit enter. Now top prompts for a pid. Enter the pid of the process you want to expedite. Hit enter. Good bye process.

Installing pip and virtualenv on Mac

These instructions show how to install pip and virtualevn on a Mac running Snow Leopard 10.6.8 and using Python 2.7. I used this to install Django 1.3.1 (installation instructions included).

Installing pip

(skip if you have pip installed)

First make sure you have either setuptools or distribute installed. Please consult your operating system’s package manager or install it manually:

curl http://python-distribute.org/distribute_setup.py | python

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Finding a route from one wikipedia page to another

Here’s a game I like to play. Select two wikipedia pages at random, and find a route from one to the other. I stated a theorem once that:

you can get from any page on wikipedia to the page on pollination in 7 steps or less. (it was actually another page, but let’s say it was pollination)

I devised a method for doing this using Google search. Let’s call the random page s, and the page you want to reach t, e.g. pollination. A given page on wikipedia has a set of incoming links (other pages linked to the page), and a set of outgoing links (other pages linked to by the page). Let’s call these two sets in[p] and out[p]. These two sets contain direct decendants and ancestors of p respectively.

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