c/c++语言开发共享Linux在c中使用管道传递父进程和子进程之间的值？

我认为要解决的第一个问题是，当您尝试读取/写入数据时，管道的两端都会打开。 如果您正在将数据写入管道

 close(fd[READ_END]) write(...) close(fd[WRITE_END]) 

其次，unix中的管道是单工的。 您似乎同时尝试从管道读取和写入。 如果你想这样做，你将不得不打开两个管道。

我修改了你的程序，向你展示如何从管道读取，然后写入父/子管道。 希望这对你有所帮助。

 #include  #include  #include  #include  #define BUFFER_SIZE 25 #define READ 0 #define WRITE 1 int main(void) { pid_t pid; //open two pipes, one for each direction int mypipefd[2]; int mypipefd2[2]; /* create the pipe */ if (pipe(mypipefd) == -1 || pipe(mypipefd2) == -1) { fprintf(stderr,"Pipe failed"); return 1; } /* now fork a child process */ pid = fork(); if (pid < 0) { fprintf(stderr, "Fork failed"); return 1; } if (pid > 0) { /* parent process */ int writeValue=10; int readValue=0; close(mypipefd[READ]); //close read end, write and then close write end write(mypipefd[WRITE],&writeValue,sizeof(writeValue)); //write to pipe one printf("Parent: writes value : %dn", writeValue); close(mypipefd[WRITE]); close(mypipefd2[WRITE]); //close write end, read, and then close read end read(mypipefd2[READ],&readValue,sizeof(readValue)); printf("Parent: reads value : %dn", readValue); close(mypipefd2[READ]); } else { /* child process */ int writeValue=20; int readValue=0; close(mypipefd[WRITE]); //close write end, read, and then close read end read(mypipefd[READ],&readValue,sizeof(readValue)); printf("child: read value : %dn", readValue); writeValue+=readValue; close(mypipefd[READ]); close(mypipefd2[READ]); //close read end, write and then close write end write(mypipefd2[WRITE],&writeValue,sizeof(writeValue)); printf("child: writeValue value : %dn", writeValue); close(mypipefd2[WRITE]); } return 0; } 

这打开两个管道。 父级将值写入第一个管道，子级读取该值。 子项更新此值，并将其写入第二个方向管道。 父母然后读取此值和vuela！ 双向管道通信。

输出：

 Parent: writes value : 10 child: read value : 10 child: write value : 30 Parent: reads value : 30 

这可以扩展到您的应用程序

  if (pid > 0) { /* parent process */ result1++; close(mypipefd[READ]); //close read end, write and then close write end write(mypipefd[WRITE],&result1,sizeof(result1)); //write to pipe one printf("Parent:nx value after operation: %dn", result1); close(mypipefd[WRITE]); close(mypipefd2[WRITE]); //close write end, read, and then close read end read(mypipefd2[READ],&result1,sizeof(result1)); close(mypipefd2[READ]); } else { /* child process */ close(mypipefd[WRITE]); //close write end, read, and then close read end read(mypipefd[READ],&result2,sizeof(result2)); result2*=10; printf("child:nx value after operation %dn", result2); close(mypipefd[READ]); close(mypipefd2[READ]); //close read end, write and then close write end write(mypipefd2[WRITE],&result2,sizeof(result2)); close(mypipefd2[WRITE]); } 

如果你把它放在循环中那么它理论上会起作用。 但是，由于上下文切换和其他与OS相关的调度，执行顺序将在两个进程之间混乱。 这意味着读取和写入不一定是您执行它的顺序，它不会工作。 阅读此问题如何等待数据写入管道的另一端 。