snmp_exporter[847]: snmp_exporter: error: unknown short flag '-c', try --help
systemd[1]: prometheus-snmp-exporter.service: Main process exited, code=exited, status=1/FAILURE

$ nix run -f channel:nixos-18.03 prometheus-snmp-exporter -c snmp_exporter --help
Usage of snmp_exporter:
  -config.file string
    	Path to configuration file. (default "snmp.yml")
  -log.format value
    	Set the log target and format. Example: "logger:syslog?appname=bob&local=7" or "logger:stdout?json=true" (default "logger:stderr")
  -log.level value
    	Only log messages with the given severity or above. Valid levels: [debug, info, warn, error, fatal] (default "info")
  -version
    	Print version information.
  -web.listen-address string
    	Address to listen on for web interface and telemetry. (default ":9116")

$ nix run -f channel:nixos-18.09 prometheus-snmp-exporter -c snmp_exporter --help
usage: snmp_exporter [<flags>]

Flags:
  -h, --help                    Show context-sensitive help (also try --help-long and --help-man).
      --config.file="snmp.yml"  Path to configuration file.
      --web.listen-address=":9116"
                                Address to listen on for web interface and telemetry.
      --log.level="info"        Only log messages with the given severity or above. Valid levels: [debug, info, warn,
                                error, fatal]
      --log.format="logger:stderr"
                                Set the log target and format. Example: "logger:syslog?appname=bob&local=7" or
                                "logger:stdout?json=true"
      --version                 Show application version.