Docker exec helper with interactive mode

dsh

#!/usr/bin/env bash

if [ $# -eq 1 ] && [ "$1" == "-h" ]; then
    echo 'dsh - wrapper for "docker exec -it CONTAINER bash".'
    echo 'Usage: dsh                   # interactive mode' 
    echo '       dsh CONTAINER         # bash'
    echo '       dsh CONTAINER cmd     # run cmd'
    exit 0
fi

if [ $# -eq 0 ]; then
    PS=$(docker ps | tail -n +2)
    if [ -z "$PS" ]; then
        echo 'There are no running containers.'
        exit 0
    fi

    echo 'Runned containers:'
    I=0
    echo "$PS" | while IFS= read -r CONTAINER ; do
        I=$(($I+1))
        echo " $I. $CONTAINER"
    done

    echo ''
    echo -n 'Choose container: '
    read NUMBER
    re='^[0-9]+$'
    if ! [[ $NUMBER =~ $re ]]; then
        echo "Invalid number."
        exit 1
    fi

    CONTAINER=$(echo "$PS" | sed -ne "${NUMBER}p")
    echo " -> $CONTAINER"
    ID=$(echo "$CONTAINER" | awk '{print $1}')
    docker exec -it $ID sh
else
    # Manual mode
    CONTAINER=$1
    if [ $# -le 1 ]; then
        docker exec -it ${CONTAINER} bash
        exit 0
    fi
    CMD=${@:2}
    docker exec -it ${CONTAINER} ${CMD}
fi
exit 0