Subscribe an e-link and output to file.

Usage:
    felix-elink2file [options] <local_hostname> <fid> <file>

Options:
    -b, --bus-dir DIRECTORY         Directory for the bus [default: ./bus]
    -g, --bus-groupname GROUP_NAME  Group name to use [default: FELIX]
    -v, --verbose                   Verbose output
    --error-out=fifo                (NI) Write error information to a UNIX FIFO

Arguments:
    <local_hostname>    Internet hostname to subscribe from
    <fid>               FID to subscribe to
    <file>              File to write to
