Edit Question - KnowledgeHub

Title Body

I am trying to implement a shell in C. I can execute simple commands just fine with a simple execvp() but one of the requirements is to manage commands like this: "ls -l | head | tail -4" with a 'for' loop and only one 'pipe()' statement redirecting stdin and stdout. Now after days I'm a bit lost. N = Number of simple commands (3 in the example: ls, head, tail) commands = a list of structs with the commands, like this: commands[0].argv[0]: ls commands[0].argv[1]: -l commands[1].argv[0]: head commands[2].argv[0]: tail commands[2].argv[1]: -4 So, I made the for loop, and started to redirect stdin and stdout in order to connect all the commands with pipes, but...I'm just clueless why it doesn't work. for (i=0; i < n; i++){ pipe(pipe); if(fork()==0){ // CHILD close(pipe[0]); close(1); dup(pipe[1]); close(pipe[1]); execvp(commands[i].argv[0], &commands[i].argv[0]); perror("ERROR: "); exit(-1); }else{ // FATHER close(pipe[1]); close(0); dup(pipe[0]); close(pipe[0]); } } What I want to create is a 'line' of childed processes: [ls -l] ----pipe----> [head] ----pipe----> [tail -4] All this processes have a root (the process runing my shell) so, the first father is also a child of the shell process, I'm a bit exhausted already, can anyone help me here please? I'm not even sure if the childs should be the ones executing the commands. Thanks guys !!

Tags (comma-separated) Cancel