/* tom.c v4.0 */#include <unistd.h>#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <stdlib.h>#include <stdio.h>#include <errno.h>#include <pthread.h>static void tid2str(char * str, pthread_t tid){  sprintf(str, "%ld", tid);}void *thread0(void *arg){  char msg[] = "I love you.\n";  pthread_t tid = pthread_self();  char stid[256];  tid2str(stid, tid);  if(fork()==0) {    if (execlp("./jerry", "jerry", stid, msg, NULL)<0) {      perror("execlp");      exit(EXIT_FAILURE);    }  }    return NULL;}void *thread1(void *arg){  char msg[] = "I love you.\n";  pthread_t tid = pthread_self();  char stid[256];  tid2str(stid, tid);  if(fork()==0) {    if (execlp("./jerry", "jerry", stid, msg, NULL)<0) {      perror("execlp");      exit(EXIT_FAILURE);    }  }    return NULL;}void *thread2(void *arg){  char msg[] = "I love you.\n";  pthread_t tid = pthread_self();  char stid[256];  tid2str(stid, tid);  if(fork()==0) {    if (execlp("./jerry", "jerry", stid, msg, NULL)<0) {      perror("execlp");      exit(EXIT_FAILURE);    }  }    return NULL;}void *thread3(void *arg){  char msg[] = "I love you.\n";  pthread_t tid = pthread_self();  char stid[256];  tid2str(stid, tid);  if(fork()==0) {    if (execlp("./jerry", "jerry", stid, msg, NULL)<0) {      perror("execlp");      exit(EXIT_FAILURE);    }  }    return NULL;}void *thread4(void *arg){  char msg[] = "I love you.\n";  pthread_t tid = pthread_self();  char stid[256];  tid2str(stid, tid);  if(fork()==0) {    if (execlp("./jerry", "jerry", stid, msg, NULL)<0) {      perror("execlp");      exit(EXIT_FAILURE);    }  }    return NULL;}int main(){  int ret, i;  pthread_t id[5];  ret = pthread_create(&id[0], NULL, thread0, NULL);  if (ret!=0) {    perror("pthread_creat");    exit(EXIT_FAILURE);  }  ret = pthread_create(&id[1], NULL, thread1, NULL);  if (ret!=0) {    perror("pthread_creat");    exit(EXIT_FAILURE);  }  ret = pthread_create(&id[2], NULL, thread2, NULL);  if (ret!=0) {    perror("pthread_creat");    exit(EXIT_FAILURE);  }  ret = pthread_create(&id[3], NULL, thread3, NULL);  if (ret!=0) {    perror("pthread_creat");    exit(EXIT_FAILURE);  }  ret = pthread_create(&id[4], NULL, thread4, NULL);  if (ret!=0) {    perror("pthread_creat");    exit(EXIT_FAILURE);  }  for (i=0; i<5; i++) {    pthread_join(id[i], NULL);  }    exit(EXIT_SUCCESS);}/** * Can function "thread0" to "thread4" merge into only one function * "thread"? * * In this case we can't. Because we need different tid and stid to * use, if we merge them into one function, then all thread will use * same variable. */