为什么父进程一直阻塞呢，
1 #include<stdio.h> 2 #include<unistd.h> 3 #include<sys/types.h> 4 int main() 5 { 6 int fd[2]; 7 pid_t pid1,pid2; 8 char *arg_net[] = {"netstat","-lant",NULL}; 9 char *env_net[] = {"PATH=/bin",NULL}; 10 char *arg_grep[] = {"grep","22",NULL}; 11 char *env_grep[] = {"PATH=/bin",NULL}; 12 if(pipe(fd) != 0) 13 exit(1); 14 if((pid1 = fork()) == 0){ 15 printf("pid1 = %d\n",getpid()); 16 close(1); 17 dup2(fd[1],1); 18 close(fd[0]); 19 close(fd[1]); 20 execve("/bin/netstat",arg_net,env_net); 21 exit(0); 22 }else if(pid1 < 0 ){ 23 printf("fork error\n"); 24 exit(1); 25 } 26 27 28 if((pid2 = fork()) == 0){ 29 printf("pid2 = %d\n",getpid()); 30 close(0); 31 dup2(fd[0],0); 32 close(fd[1]); 33 close(fd[0]); 34 execve("/bin/grep",arg_grep,env_grep); 35 exit(0); 36 }else if(pid2 < 0){ 37 printf("fork error\n"); 38 exit(2); 39 } 40 printf("parent = %d\n",getpid()); 41 waitpid(pid1,NULL,0); 42 waitpid(pid2,NULL,0); 43 return 0; 44 }