Use a Dot Matrix Printer to print Tweets as they happen

TwitterMatrixTicker.sh

#!/bin/sh
# Kenneth Finnegan, 2012
# kennethfinnegan.blogspot.com
# adapted for osx by 0x6d64, 0x6d64@arcor.de
#
# TwitterMatrixTicker
# Given a username and an ascii printer, checks for new mentions and
# prints them one at a time to the printer.
# Expected usage is either spun off into the background >/dev/null or
# on a detachable screen so you can monitor progress.

# What user do we want to monitor for tweets at?
USEROFINTEREST="kwf"

# File paths. The staging is needed since tweets come in
# the opposite order from what I wanted; tac (cat backwards) fixes that
LATESTTWEET="/tmp/twittermatrixticker.latest.$USEROFINTEREST"
STAGING_FILE="/tmp/twittermatrixticker.staging.$$"
OUTPUT_FILE="/dev/usb/lp0"

# Twitter API requests are made progressively slower as no traffic
# is seen. INTERVAL is the number of seconds between tweets, so API
# requests are really made at INTERVAL * REQUEST_LIMIT seconds
LATESTUSER=""
INTERVAL="10"
INTERVAL_LOW="10"
INTERVAL_HIGH="150"
REQUEST_LIMIT="5"

# Check if this is the first time this user's timeline has
# been monitored, preload the state file for twitter timeline progress
if [ ! -f $LATESTTWEET ]; then 
	echo "Generating new state file for @$USEROFINTEREST"
	curl -s "http://search.twitter.com/search.json?q=@$USEROFINTEREST&rpp=$REQUEST_LIMIT&include_entries=true&result_type=recent" |
	grep -oe "\"max_id_str\":\"[^\"]*\"" |
	awk -F'\"' '{print $4}' >$LATESTTWEET
else
	echo "The last tweet displayed was `cat $LATESTTWEET`"
fi

# Loop forever checking for tweets, printing them, then sleeping
while true; do
	echo "TwitterMatrixTicker with $INTERVAL second interval"
	touch $STAGING_FILE
	# Form the twitter request
	curl -s "http://search.twitter.com/search.json?q=@$USEROFINTEREST&rpp=$REQUEST_LIMIT&include_entries=true&result_type=recent&since_id=`cat $LATESTTWEET`" |
	sed 's/\\\"/#/g' | 
	sed 's/\`/#/g' | 
	sed 's/\\/#/g' | 
	tee /tmp/twittermatrixticker.debug.$$ |
	# Parse out the user names, their tweets, and the latest id number
	grep -o -e "\"text\":\"[^\"]*\"\|\"from_user\":\"[^\"]*\"\|\"max_id_str\":\"[^\"]*\"" |
	# loop through the set of found items and handle them
	while read LINE; do
		FIELD="`echo $LINE | awk -F'\"' '{print $2}'`"
		VALUE="`echo $LINE | awk -F'\"' '{print $4}'`"
		
		if [ $FIELD = "from_user" ]; then
			# We know who sent the next tweet we see; save this
			LATESTUSER="$VALUE"
		elif [ $FIELD = "text" ]; then
			# We've found a tweet; stage this with cooresponding username
			echo "$LATESTUSER: $VALUE" >>$STAGING_FILE
			echo "Found tweet"
		elif [ $FIELD = "max_id_str" ]; then
			# Save the highwater mark from this request so we can pick up
			# where we left off later.
			echo "$VALUE" >$LATESTTWEET
			echo "The latest tweet is now $VALUE"
		fi
	done

	# Count how many tweets we ended up with, print them, then update
	# the desired interval rate and sleep out the remainder of this
	# interval if we didn't happen to get a complete REQUEST_LIMIT of tweets
	TWEETSFOUND="`wc -l <$STAGING_FILE`"
	echo "Tweets found: $TWEETSFOUND"

	# Reverse tweets into cronological order, and print them one by one
	tail -rn 1000 $STAGING_FILE |
	while read LINE; do
		echo "$LINE" >$OUTPUT_FILE
		# Spread out printings so I can feel more popular
		# and it seems less bursty
		sleep "$INTERVAL"
	done
	rm $STAGING_FILE

	# Check to see if there was new tweets in this request
	# If not, slow down requests, since this user doesn't get much traffic
	if [ $TWEETSFOUND = "0" ]; then
		echo "Slow it down"
		INTERVAL="$(($INTERVAL + 1))"
		if [ "$INTERVAL" -gt "$INTERVAL_HIGH" ]; then
			INTERVAL="$INTERVAL_HIGH"
		fi
	else # Found some, speed up the requests
		echo "Speed it up"
		INTERVAL="$(( $(( $INTERVAL / 2)) + $((INTERVAL_LOW / 2)) ))"
	fi

	TIME_LEFT="$(( $(( $REQUEST_LIMIT - $TWEETSFOUND)) * $INTERVAL ))"
	sleep "$TIME_LEFT"
done

This version of the script should work under OS X. I tested it only using a dummy file simulating a printer, so any feedback is appreciated!