c - Calling system() from threads with while using ZeroMQ -

i having strange problem c zeromq on os x. using "multithreaded service in c" code guide , have added call system("ls") after sleep(1) call in worker_routine function. function looks this:

static void * worker_routine (void *context) {     //  socket talk dispatcher     void *receiver = zmq_socket (context, zmq_rep);     zmq_connect (receiver, "inproc://workers");      while (1) {         char *string = s_recv (receiver);         printf ("received request: [%s]\n", string);         free (string);         //  'work'         sleep (1);         system("ls");         //  send reply client         s_send (receiver, "world");     }     zmq_close (receiver);     return null; } 

when connect server sample client in guide, ls runs s_send fails noent error , no more requests handled. if remove system("ls") call works fine.

does know might going on?

thanks, steve

system not thread-safe. see sample implementation in posix understanding of why it's not , can't be:

http://pubs.opengroup.org/onlinepubs/9699919799/functions/system.html

in particular, changes signal dispositions, process-global resource.

it's possible output of ls going somewhere causes problem. intend output go? replacement system popen, allows read output of command , process or send wherever want.