tom.c

用五个实例来解释linux下的c编程

/* 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.
 */