pipic/client/client.sh

#!/bin/sh

REMOTE='http://localhost:8080'
INTERVAL=1

requirecmd()
{
	which "$1" 2>1 > /dev/null
	if [ "$?" -ne 0 ]; then
		echo "Missing command: $1"
		exit 1
	fi
}

requirecmd curl
requirecmd fbv
requirecmd shasum

calchash()
{
	shasum --algorithm 1 "$1" 2>/dev/null | cut -d ' ' -f 1
}

PICFILE="pic"
PICHASH=$(calchash "$PICFILE")
PROGPID=$$

# Loop responsible for requesting to the server
# and updating the picture if necessary
requestloop()
{
	while :; do
		URL="$REMOTE/$PICHASH"
		curl --silent "$URL" > refresh

		# Empty response means the file hasn't changed
		if [ $(file refresh | cut -d ' ' -f 2) = "empty" ]; then
			rm refresh

		# If the response is non-empty, we received an image file.
		# We move that file to $PICFILE, then display it
		else
			mv refresh "$PICFILE"
			PICHASH=$(calchash "$PICFILE")
			pkill --parent "$PROGPID" fbv
		fi
		sleep "$INTERVAL"
	done
}

requestloop &

while :; do
	if [ -f "$PICFILE" ]; then
		fbv --noclear --noinfo "$PICFILE"
	else
		sleep 2;
	fi
done