为什么我的 while(read) 循环管道永远不会结束？

Question

// Some initialization

// Child process
// stdin is redirected to fd[0]
while (fgets(someCharArray, sizeof(someCharArray), stdin) {
    printf("%s\n", someCharArray);
}

// Parent process
char greeting[50] = "hello\n\0";
write(fd[1], greeting, sizeof(greeting));
close(fd[1]);

I'm really baffled by these pipes. fgets should read up to and including the newline. It reads, and successfully prints "hello". However, the process doesn't end. I've closed the write end of the pipe of the parent. So it should return 0 or EOF , and the while loop should exit.

I've tried different combinations of "hello" with and without the newline character and null-terminator. I really don't see what the problem is.

Answer 1

In order to have fd[0] reach EOF you need to have closed fd[1] in all the processes who know them. In your case you should close fd[1] in the child process right after the fork()

if (fork() == 0)
{
    close(fd[1]);
    // ...
    // instructions for child process
    exit 0;
}