关于进程间通信的Linux小程序

微信(小程序)  /  管理员 发布于 5年前   271

利用工作之余为小伙伴写了份作业，关于进程间通信的。题目如下：

“父进程从键盘上接受1000个数据，对其求和sum1，子进程对这1000个数平方和sum2，结果传给父进程，父进程将sum1+sum2后，打印结果。”

要求：用大小为10的共享区传递1000个数据；子进程用消息机制将sum2传给父进程。 

主要利用共享内存实现进程间通信，使用管道实现进程间竞争关系，FreeBSD下测试通过。代码如下：时间有限，有可能有些不足，希望高手给予指点。

#include <stdio.h>#include <string.h>#include <stdlib.h>#include <sys/shm.h>#include <signal.h>const int key = 0x12345678;static int pfd1[2], pfd2[2];#define SHM_LEN (10*1024)#define VAL_NUM 5int init_shm() { int shmid = -1; shmid = shmget((key_t)key, SHM_LEN, 0666 | IPC_CREAT); if (shmid < 0) {  printf("shmget failed!\n");  exit(-1); } return shmid;}void cancel_shm(int shmid) { if (shmctl(shmid, IPC_RMID, 0) == -1) {  printf("shmctl failed!\n");  exit(-1); }  printf("cancel_shm successfully!\n");}void *shm_get(int shmid) { void *mem = NULL; mem = shmat(shmid, 0, 0); if (mem == (void *)-1) {  printf("shmat failed!\n");  exit(-1); } return mem;}int get_val(int *val, int num) { int i; for (i = 0; i < num; i++) {  printf("please input a num:");  scanf("%d", val + i); }}void show_val (int *val, int num) { int i; for (i = 0; i < num; i++) {  printf("%d\t", *(val + i)); } printf("\n");}int add_val (int *val, int num) { int result = 0; int i;  for (i = 0; i < num; i++) {  result += *(val + i); } return result;}int square_val (int *val, int num) { int result = 0; int i, tmp; for (i = 0; i < num; i++) {  tmp = *(val + i);  result += (tmp * tmp); } return result;}void TELL_WAIT (void) { if (pipe(pfd1) < 0 || pipe(pfd2) < 0) {  printf("pipe error!\n");  exit(-1); }}void TELL_PARENT (pid_t pid) { if (write(pfd2[1], "c", 1) != 1) {  printf("write error!\n");  exit(-1); }}void WAIT_PARENT (void) { char c; if (read(pfd1[0], &c, 1) != 1) {  printf("read error!\n");  exit(-1); }}void TELL_CHILD (pid_t pid) { if (write(pfd1[1], "p", 1) != 1) {  printf("write error!\n");  exit(-1); }}void WAIT_CHILD (void) { char c; if (read(pfd2[0], &c, 1) != 1) {  printf("read error!\n");  exit(-1); }}int main(int argc, char *argv[]) { void *mem = NULL; int shmid = -1; pid_t pid = -1; int val[VAL_NUM]; int result = 0; shmid = init_shm();  TELL_WAIT(); if ((pid = fork()) < 0) {  //error  printf("fork error!\n");   exit(-1); } else if (pid == 0) {   //child  int result = 0;  WAIT_PARENT();  mem = shm_get(shmid);  //get share memery  memcpy(val, mem, sizeof(int) * VAL_NUM);  result = square_val(val, VAL_NUM);   *(int *)((void *)mem + SHM_LEN - 4) = result;  TELL_PARENT(pid);  exit(1); } else {      //parent  int child_result = 0;  mem = shm_get(shmid);  //get share memery  get_val(val, VAL_NUM);  //get user input  memcpy(mem, val, sizeof(int) * VAL_NUM); //copy user input to share memery  TELL_CHILD(pid);  result = add_val(val, VAL_NUM);  WAIT_CHILD();  child_result = *(int *)((void *)mem + SHM_LEN - 4);  printf("result:%d, child_result:%d, all:%d\n", result, child_result, result + child_result); } cancel_shm(shmid); return 0;}

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