function help()
{
    echo -e "\nERROR:  ${1}\nYou must provide a file that can be accessed from within the Docker container.  This is possible for files that\n\t- Have a path in \${HOME} or\n\t- Have a full file path that begins with one of \"/hosthome/\", \"/opt/lofar2.0/tango/\" or \"/opt/lofar2.0/\".\n\nWhy is that?  Because the file will be loaded from within the Docker container and only some of the host's file system directories are mounted in the container."
    exit -2
}

if [ ${#} -eq 1 ]; then
    file=${1}
else
    help "A file name must be provided."
fi

# Check if the filename begins with /hosthome/, /opt/lofar2.0/tango or
# /opt/lofar2.0/ or if it is in the ${HOME} directory:
if [ ${1:0:10} != /hosthome/ -a ${1:0:20} != /opt/lofar2.0/tango/ -a ${1:0:14} != /opt/lofar2.0/ ]; then
    pushd $(dirname ${file}) >/dev/null
    full_path=${PWD}
    popd >/dev/null
    # Check if the file's directory begins with ${HOME}.  Then it can be
    # accessed via /hosthome.  The replacement will then shorten the result.
    home_replaced=${full_path#${HOME}}
    if [ ${#home_replaced} -ne ${#full_path} ]; then
        if [ ! -f ${file} ]; then
            help "The file \"${1}\" does not exist."
        fi

        # The file can be accessed through /hosthome.  Modify the parameter.
        file=/hosthome${home_replaced}/$(basename ${file})
    else
        # The file is in one of the two:  /opt/lofar2.0/tango/ /opt/lofar2.0/
        # Provide the full path since it is accessible from within the docker
        # image because both directories are mounted.
        file=${full_path}/$(basename ${file})
    fi
fi

docker exec -it ${TANGO_CONTAINER_ENV} dsconfig json2tango --write --update ${file}