Left-Fold for Bash

I'd like to share a recent bash programming experience I've had. It began while processing the reams of data generated in my M.Sc. research study. I was producing long lists of frequency data in text files, and had the need to sum up all the lines in these tables. This is of course a trivial problem in many languages, and I had a wide array of options available to me:

• I could write another ant task to do the summing (this required more work that I was willing to invest, as ant isn't really suited for computational tasks)
• I could write a python script that took the contents of the specified file and returned the sum. I didn't really like this approach because it involved yet another file in my build process, invoked from the ant task. I always sort of thought that if you were forced to use , you were performing a task beyond the scope of your tool.
• I could skip the generation of the table and go straight to the sum. A few of the tables were created with XSLT, so this was a valid option. However, my XSLT programming ability is very much trial-and-error based, so I thought this might take some time. Also, some of the other tables, created with grep would not be affected.
  
• Write it in shell. I liked this idea. I really liked the feel of being able to just pipe something to 'sum' and have the sum returned. So this is what I chose.

My first version looked like this:

#!/bin/bash

sum=0
while read line
do
sum=$(($sum + $line))
done

echo $sum
exit 0

It did the trick quite well. I had suggestions from office mates for the following alternatives:
Using python (courtesy Aran Donohue):

python -c "import sys;print sum(float(x) for x in sys.stdin.read().split())"

Using tr (courtesy Zak Kincaid):

cat numbers | tr '\n' '+'|head --bytes='-1'|bc
(Note that this version doesn't quite work. bc throws a syntax error. not exactly sure why.)

Using my original design, I realized that if I abstracted out the operator, I could use this script to perform any 2-operand function I wished on the list, essentially creating a basic left fold:

#!/bin/bash
op=""
if [ "$1" == "" ]; then
op="+"
else
op=$1
fi

sum=0
while read line
do
sum=$(($sum$op$line))
done

echo $sum
exit 0

I've done a little bit of error checking, to see if the parameter supplied is blank, and if so replace it with + by default.

I've only seen this work for '+' and '-'. If I use '*', it breaks because it replaces the wildcard/multiplication character with the listing of the current directory.

Code Monkies and the Recipe for Happiness

Hanging out in my office today. Being moderately productive, but in an inexplicably good mood. The apparent recipe for happiness is as follows:

1. Purchase a ridiculously expensive bagel
2. Coffee
3. Install shiny new operating system on laptop
4. Meet with supervisor
5. Coffee
   
6. Create UI mockups for hypothetical testing tool
7. Listen to 'Code Monkey' by Jonathan Coulton a few hundred times.
8. Coffee

I like this song. It gives me this mental image of developers as knuckle-dragging primates. Especially the way Coulton removes all articles from the lyrics of the song. Ex. "Code monkey get up, get coffee." And after all, if you can't laugh at yourself, at whom can you laugh? (sentences also can't end in prepositions). A couple excerpts:

"Rob says Code Monkey very diligent, but his output stink. Code Monkey's code not functional or elegant. What do Code Monkey think? Code Monkey think maybe manager want to write god damn login page himself? Code Monkey not say it out loud. Code Monkey not crazy, just proud!"

"Much rather wake up, eat coffee cake. Take bath. Take nap. This job fulfilling in creative ways. What a load of crap."