ressh

#!/usr/bin/env bash
################################################################################
# ressh - maintain a persistent SSH connection.  Could be used with something
# like tmux or screen to have an automatically-attached terminal session, even
# while switching between networks/interfaces.
#
# Version 2
# Matthew Malensek <matt@malensek.net>
################################################################################
# Default Options (set RESSH_OPTS to override)
# Close hung connections quickly:
ssh_options="${RESSH_OPTS:--oServerAliveInterval=1 -oServerAliveCountMax=3 -t}"
sleep_time=1
unset verbose
################################################################################

script_name=$(basename ${0})

print_usage() {
cat <<EOM
Usage: ${script_name} [options] [user@]hostname [ssh-options] command
    -s <number>    Seconds to sleep between connection retries. \
Default: ${sleep_time}
    -v             Verbose output; don't clear the screen
EOM
}

while getopts "s:v" flag; do
    case ${flag} in
        s) sleep_time=${OPTARG} ;;
        v) verbose=1 ;;
        ?) print_usage; exit 1 ;;
    esac
done

shift $(($OPTIND - 1))

# make sure we have at least 2 parameters
if [[ ${#} -lt 2 ]]; then
    print_usage
    exit 1
fi

destination=${1}
shift

while true; do
    ssh ${ssh_options} ${destination} ${@}
    # exit status is 255 if an error occurred; otherwise the remote command
    # returned successfully.
    if [[ ${?} -eq 255 ]]; then
        [[ -n ${verbose} ]] || clear

        echo "${script_name}: Connection Error! Retrying..."
        sleep ${sleep_time}
    else
        break
    fi
done