87 lines
2.3 KiB
C
87 lines
2.3 KiB
C
#include<unistd.h>
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#include<signal.h>
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#include<stdio.h>
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#include<string.h>
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#include<stdlib.h>
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#include<sys/wait.h>
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#include<semaphore.h>
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#include<sys/sem.h>
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#include <sys/stat.h>
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#include<fcntl.h>
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int main(){
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int pid1,pid2;
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sem_t *resource1;
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sem_t *resource2;
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char inpipe[200],outpipe1[100],outpipe2[100];
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int fd[2]; //0为读出段,1为写入端
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pipe(fd); //建立一个无名管道
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pid1 = fork();
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if(pid1<0){
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printf("error in the first fork!");
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}
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else if(pid1==0){ //子进程1
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printf("[%s|%u]Current: %u\n", __FUNCTION__, __LINE__, getpid());
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printf("Pid of PID[1]: %u\n", getpid());
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resource1=sem_open("name_sem1",O_CREAT,0666,0); // 有名信号量打开，name_sem1
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close(fd[0]); //关掉读出端
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lockf(fd[1],1,0); // 管道持锁, 锁定从当前偏移量到文件结尾的区域
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sprintf(outpipe1,"Child process 1 is sending a message!\n");
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write(fd[1],outpipe1, strlen(outpipe1));
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lockf(fd[1],0,0); // 管道解锁
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sem_post(resource1); // 信号量开锁，name_sem1
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sem_close(resource1); // 有名信号量关闭，name_sem1
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exit(0); // 线程退出
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}
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pid2 = fork();
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if(pid2<0){
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printf("error in the second fork!\n");
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}else if(pid2==0){ // 子进程2
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printf("[%s|%u]Current: %u\n", __FUNCTION__, __LINE__, getpid());
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resource1=sem_open("name_sem1",O_CREAT,0666,0);
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resource2=sem_open("name_sem2",O_CREAT,0666,0);
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sem_wait(resource1);
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printf("Pid of PID[2]: %u\n", getpid());
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close(fd[0]);
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lockf(fd[1],1,0);
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sprintf(outpipe2,"Child process 2 is sending a message!\n");
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write(fd[1],outpipe2, strlen(outpipe2));
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lockf(fd[1],0,0);
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sem_post(resource2);
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sem_close(resource1);
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sem_close(resource2);
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exit(0);
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}
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if(pid1 > 0 && pid2 >0){
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printf("[%s|%u]Current: %u\n", __FUNCTION__, __LINE__, getpid());
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resource2=sem_open("name_sem2",O_CREAT,0666,0);
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sem_wait(resource2); // 信号量持锁，source2
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printf("Current: %u\n", getpid());
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waitpid(pid1,NULL,0); // 等待子线程1状态变化(退出)；
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waitpid(pid2,NULL,0); // 等待子线程2状态变化(退出)；
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close(fd[1]); //关掉写端
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read(fd[0],inpipe,200);
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printf("%s\n",inpipe);
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sem_close(resource2);
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exit(0); // 进程退出，正常
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}
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sem_unlink("name_sem1"); // 信号量销毁，
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sem_unlink("name_sem2");
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return 0;
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}
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