wait-for-port.sh

#!/bin/bash


trap "echo interrupted && exit 2" INT TERM QUIT

limit=100
op=open

while getopts ":csw:" opt; do
    case $opt in
        c) op=close
            ;;
        s) silence=1
            ;;
        w) limit=$OPTARG
            ;;
        :) echo "$0: option requires an argument -- '$OPTARG'" >&2
            exit 1
            ;;
        *) echo "$0: invalid option -- '$OPTARG'" >&2
            exit 1
            ;;
    esac
done
shift $((OPTIND-1))

if [[ $# -lt 2 ]]; then
    cat <<EOF
    usage: wait-for-port.sh [OPTION]... HOST PORT...

    -c        wait until the port is closed. Otherwise wait until for opening.
    -s        silent mode
    -w COUNT  If number of retrying operation exceeds COUNT exit with exit code 1.
    by default, COUNT is 100.  Use -1 for unlimited waiting)
EOF
    exit 1
fi

host=$1
shift

for port in $@; do
    test -z ${silence} && echo -n Wait for TCP ${host}:${port} ${op}...

    tries=0
    while true; do
        if [[ ${limit} -gt 0 && ${tries} -ge ${limit} ]]; then
            failed=1
            break
        fi
        timeout --foreground 0.5 bash -c "echo > /dev/tcp/${host}/${port}" &>/dev/null
        ret=$?
        [ ${op} = close ] && [ ${ret} -ne 0 ] && break
        [ ${op} = open  ] && [ ${ret} -eq 0 ] && break
        sleep 1
        ((tries++))
    done

    if [[ -z ${silence} ]]; then
        if [[ -z ${failed} ]]; then
            echo done
        else
            echo failed
        fi
    fi

    [[ -n ${failed} ]] && exit 1
done
exit 0