Wait for a TCP port to be open

wait-tcp.sh

#!/bin/bash

function help {
	echo "Usage: wait-for port [timeout]"
	echo "       port is a TCP port number, or the service name (for instance http, ssh)"
	echo "       timeout is expressed in seconds"
	echo "             optional (defaulted to 30)"
	echo "             if <= 0, no timeout"
	exit 1
}

if [ $# -eq 0 ]; then
	help
fi

PORT=$1

# timeout in seconds
TIMEOUT=30
if [ $# -ge 2 ]; then
	TIMEOUT=$2
fi

SLEEP=1s

function now {
	date +%s
}

startTime=$(now)

function checkTimeout {
	if [ $TIMEOUT -gt 0 ]; then
		current=$(now)
		elapsed=$(( $current - $startTime ))
		if [ $elapsed -ge $TIMEOUT ]; then
			echo "Timeout"
			exit 2
		fi
	fi
}

function checkPort {
	fuser $PORT/tcp 2>/dev/null | wc -c
}

if [ $(checkPort) = 0 ]; then
	echo "Waiting for TCP port $PORT"
fi

while [ $(checkPort) = 0 ]
do
  checkTimeout
  sleep $SLEEP
done

OWNER=$(fuser $PORT/tcp 2>/dev/null | sed -e 's/\s*//g')
echo "$OWNER"

Blocks until a program has successfully open the choosen TCP port.

Supports timeout in seconds.
Cleaner output.
Inline help if missing args.

Licensed under the DO WHAT THE FUCK YOU WANT WITH THIS License :o)