val check_output :
?on_wrong_status:loglevel->?on_nonempty_stdout:loglevel->?on_nonempty_stderr:loglevel->?on_ok:loglevel->?command:string ->output->
unit
val run :
?timeout:float ->?env:string array->?cwd:string ->?stdin:string ->?on_wrong_status:loglevel->?on_nonempty_stdout:loglevel->?on_nonempty_stderr:loglevel->?on_ok:loglevel->string list->outputLwt.t