[Bro-Dev] #583: system function with feedback

[Gilbert Clark]

I think I'd be worried about spawning too many long-running background 
processes and hitting the process fd limit (default is 1024 on Linux, I 
think?).

Counter-proposal: fork(), configure pipes (dup2, I think?), exec(), and 
then wait for SIGCHLD.  Alternatively, since the timer would allow for a 
poll every so often, could possibly mask SIGCHLD away and just do a 
waitpid with WNOHANG in the fired timing event to loop over all the bg 
processes and report on the ones that are done.  I can't remember enough 
about fork and SIGCHLD to know exactly how kosher the second option is, 
though, so YMMV.

--Gilbert

On 9/1/2011 1:28 PM, Bro Tracker wrote:
> #583: system function with feedback
> -----------------------------+--------------------
>   Reporter:  seth             |      Owner:
>       Type:  Feature Request  |     Status:  new
>   Priority:  Normal           |  Milestone:  Bro1.7
> Component:  Bro              |    Version:
>   Keywords:  language         |
> -----------------------------+--------------------
>   Jon and I just came up with a proposal for talking to external processes
>   and getting results.  Our idea is to center it around running the external
>   process in the background as it's done now then redirecting stdin and
>   stdout to temporary files and to have a file handle where the exit code
>   will be available.  Bro could poll using timers for the exit code to
>   indicate the external process has completed then an event would be
>   generated.  Here is an example of using this function/event combination:
>
>   {{{
>   global called_procs: table[string] of string = {};
>
>   # These are the prototypes for the function and event that need to be
>   added
>   # to the core.  The names are both terrible.
>   global piped_exec_with_result: function(uid: string, program: string,
>   to_write: string);
>   global system_result: event(uid: string, exit_code: int, stdout: string,
>   stderr: string);
>
>   event bro_init()
>           {
>           local uid = unique_id("");
>           called_procs[uid] = "date";
>           piped_exec_with_result(uid, "date", "");
>           }
>
>   event system_result(uid: string, exit_code: int, stdout: string, stderr:
>   string)
>           {
>           print fmt("The command line %s was run and exited with %d.",
>   called_procs[uid], exit_code);
>           print fmt("    On stdout: %s", stdout);
>           print fmt("    On stderr: %s", stderr);
>           }
>   }}}
>