title: WHy are my processes behaving like this?
body: <p>it's some implementation of linux shell in c. Since i have added background process support i have some output that i fail to understand. Here is the code:</p>
  
  <pre><code>#include &lt;stdlib.h&gt;
  #include &lt;errno.h&gt;
  #include &lt;stdio.h&gt;
  #include &lt;stdlib.h&gt;
  #include &lt;string.h&gt;
  #include &lt;unistd.h&gt;
  #include &lt;sys/types.h&gt;
  #include &lt;sys/time.h&gt;
  #include &lt;sys/resource.h&gt;
  #include &lt;signal.h&gt;
  #include &lt;wait.h&gt;
  
  #define DEFAULT_PROMPT "\nLog710H2014%&gt;"
  #define EXIT_CMD "exit"
  #define CD_CMD "cd"
  #define HOME_ENV_VAR "HOME"
  #define NEW_LINE "\n**************************************************\n"
  #define BCG_CMD_FLAG "&amp;"
  
  void cd_handler(int argc, char *argv[]);
  int lire(char *chaine, int longueur);
  char** init_command(int* size,char *str);
  int execProg(int *argc, char **argv);
  int execProgBg(int *argc, char **argv);
  void sigchldHandler(int sig_num);
  
  struct beanProcess {
      pid_t pid;
      int job_num;
      char *command;
  };
  
  struct beanProcess *beans;
  
  int jobCount = 1;
  
  int main() {
  
      printf(NEW_LINE);
      printf("Bienvenue sur le shell de l'equipe 1");
      printf(NEW_LINE);
  
      while(1){
          char str[200];
          printf(DEFAULT_PROMPT);
  
          lire(str, 200);
          int commArgsC = 0, bg = 0;
          char** comms  = init_command(&amp;commArgsC, str);
  
          if(commArgsC == 0){
              printf("Saisie vide, veuillez entrez une commande.");
              continue;
          }
  
          if(strcmp(comms[commArgsC-1], BCG_CMD_FLAG) == 0){
              bg = 1;
              comms[commArgsC-1] = 0;
          }
          if(strcmp(comms[0], CD_CMD) == 0){
              cd_handler(commArgsC, comms);
              commArgsC = commArgsC -1;
          }
          else if (strcmp(comms[0], EXIT_CMD) == 0){
              exit(0);
          }
          else {
              if(bg){
                  execProgBg(&amp;commArgsC, comms);
              }
              else{
                  execProg(&amp;commArgsC, comms);
              }
          }
      }
      exit;
  }
  void cd_handler(int argc, char *argv[]){
      char buff[512];
      char * directory;
  
      if(argc &lt; 2){
          directory  = getenv(HOME_ENV_VAR);
      }else if (argc == 2){
          directory = argv[1];
      }else{
          exit(1);
      }
  
      if (chdir(directory) == -1) {
          printf ("Erreur de changement de repertoire actif", strerror (errno));
      }else{
          if (getcwd(buff, sizeof(buff)) == NULL)
              perror("Impossible d'afficher le repertoire courant");
          else
              printf("le repertoire courant est: %s\n", buff);
      }
  }
  //Cette fonction est adaptée a partir du code de refp sur http://stackoverflow.com/questions/11198604/c-split-string-into-an-array-of-strings
  char** init_command(int* size, char* str){
      char ** res  = NULL;
      char *  p    = strtok (str, " ");
      int n_spaces = 0;
  
      while (p) {
          res = realloc (res, sizeof (char*) * ++n_spaces);
  
          if (res == NULL){
              exit (-1);
          }
          res[n_spaces-1] = p;
          p = strtok (NULL, " ");
      }
      res = realloc (res, sizeof (char*) * (n_spaces+1));
      res[n_spaces] = 0;
      *size = n_spaces;
      return res;
  }
  //cette fonction est tirée d'un exemple de http://fr.openclassrooms.com/informatique/cours/apprenez-a-programmer-en-c/recuperer-une-chaine-de-caracteres
  int lire(char *chaine, int longueur)
  {
      char *positionEntree = NULL;
  
      if (fgets(chaine, longueur, stdin) != NULL)
      {
          positionEntree = strchr(chaine, '\n');
          if (positionEntree != NULL)
          {
              *positionEntree = '\0';
          }
          return 1;
      }
      else
      {
          return 0;
      }
  }
  int execProg(int *argc, char **argv){
      char path[] = "/bin/";
      strcat(path,argv[0]);
      printf("\nThis is the %d process executing the code in non bg mode\n", getpid());
      printf("Voici le resultat de l'execution de votre commande\n");
      pid_t  pid;
      pid = fork();
  
      if (pid &lt; 0) {
          perror("Creation de processus avec fork echouee");
          exit(-1);
      }
      else if (pid == 0) {
          if(execvp(argv[0], argv) == -1){
              printf("\nthis is the child process %d executing the command in non bg mode\n", getpid());
              perror("execv");
              return EXIT_FAILURE;
          }
      }
      else {
          printf("\nthis is the parent process %d showing the stats in non bg mode\n", getpid());
          struct rusage rusg;
          long temp, tempCpu;
          wait (NULL);
          getrusage(RUSAGE_CHILDREN, &amp;rusg);
          printf("\nStatistique de la commande %s:\n", argv[0]);
  
          temp = (rusg.ru_utime.tv_sec * 1000) + (rusg.ru_utime.tv_usec / 1000);
          tempCpu = (rusg.ru_stime.tv_sec * 1000) + (rusg.ru_stime.tv_usec / 1000);
  
          printf("\nLe temps wall-clock (ms): %ld", temp);
          printf("\nLe temps CPU (ms) %ld", tempCpu);
          printf("\nNB interruptions volontaires: %ld", rusg.ru_nvcsw);
          printf("\nNB interruptions involontaires: %ld", rusg.ru_nivcsw);
          printf("\nNB defaults de pages: %ld", rusg.ru_majflt);
          printf("\nNB defaults de pages satifaits du noyau : %ld", rusg.ru_minflt);
      }
      return EXIT_SUCCESS;
  }
  int execProgBg(int *argc, char **argv){
  
      signal(SIGCHLD, sigchldHandler);
      printf("\nThis is the %d process executing the code in  bg mode\n", getpid());
  
      pid_t  pid;
      pid = fork();
  
      if (pid &lt; 0) {
          perror("Creation de processus avec fork echouee");
          return EXIT_FAILURE;
      }
      else if (pid == 0) {
          //printf("This is the pid %d", getpid());
          printf("\nthis is the child process %d executing the command in  bg mode\n", getpid());
  
          if(execvp(argv[0], argv) == -1){
              perror("execvp");
              return EXIT_FAILURE;
          }
      }
      else {
          printf("\nthis is the parent process %d showing the queue in bg mode\n", getpid());
  
          printf("[%d] %d", jobCount, pid);
          jobCount++;
          //cleanJobList(childPid);
  
          //ajoutProcess();
      }
      return EXIT_SUCCESS;
  }
  void sigchldHandler(int sig_num)
  {
      int status;
      int childPid;
      childPid = waitpid(-1, &amp;status, 1);
      printf("Hello the process %d has died\n", childPid);
      //cleanJobList(childPid);
  }
  </code></pre>
  
  <p>When i execute a bg command like "ls &amp;", here's the output:</p>
  
  <pre><code>**************************************************
  Bienvenue sur le shell de l'equipe 1
  **************************************************
  
  Log710H2014%&gt;ls &amp;
  
  This is the 23464 process executing the code in  bg mode
  
  this is the parent process 23464 showing the queue in bg mode
  [1] 23472
  Log710H2014%&gt;
  this is the child process 23472 executing the command in  bg mode
  Debug  PARTIE3.c
  Hello the process 23472 has died
  
  This is the 23464 process executing the code in non bg mode
  Voici le resultat de l'execution de votre commande
  
  this is the parent process 23464 showing the stats in non bg mode
  Debug  PARTIE3.c
  
  Statistique de la commande ls:
  
  Le temps wall-clock (ms): 0
  Le temps CPU (ms) 2
  NB interruptions volontaires: 2
  NB interruptions involontaires: 9
  NB defaults de pages: 0
  NB defaults de pages satifaits du noyau : 644
  Log710H2014%&gt;
  </code></pre>
  
  <p>Why is that the parent process overlapping  the lire() function and going directly to execProg function after the first execution ? </p>