Using waitpid to run process in background?
c, process, waitpid
Solution
I don't think `waitpid(-1, &cstatus, WNOHANG);` does what you think it does. You need to check its return value. If it is `> 0`, that's the PID of the child process that has exited. If it's `0` or `-1`, no child process has changed state.
You can just call `waitpid(-1, &cstatus, WNOHANG);` before and/or after each command you run. Call it in a loop to catch more than one child exit.
You can also handle SIGCHILD. Your process will receive this signal immediately after a child exit, which is good if you want to report child process termination immediately, without waiting for user's input.
Problem
I am trying to mimic the bash feature of running process in the background if "&" is found at the end of the command. I have the following function...and I don't think it's doing what I want it to do ``` int execute(char* args[],int background,int *cstatus){ pid_t child; pid_t ch; /*Pid of child returned by wait*/ if ((child = fork()) == 0){ /*Child Process*/ execvp(args[0],args); fprintf(stderr, "RSI: %s: command not found\n",args[0]); /*If execvp failes*/ exit(1); }else{ /*Parent process*/ if (child== (pid_t)(-1)) { fprintf(stderr,"Fork failed\n"); exit(1); }else{ if (background==0){ /*If not running in background..wait for process to finish*/ ch = wait(cstatus); }else{ printf("%ld Started\n",(long)getpid()); /* printf("Parent: Child %ld exited with status = %ld\n", (long) ch, (long)cstatus); */ }} } return 0; } int wait_and_poll(int *cstatus){ pid_t status; status = waitpid(-1,cstatus,WNOHANG); if (status>0){ fprintf(stdout,"%ld Terminated.\n",(long) status); } return 0; } ``` If i just run "ls -l " it works as expected..but if I want to run ls in the background..and have the program keep accepting new commands I call the function with background flag set as 1 and I want it to run the process in the background, tell me that it has created the process..and then prompt to accept next command.