Open() with O_WRONLY 块，即使我在另一端用 O_RDONLY open()

Question

我正面临标题所说的确切问题。

代码

pid_t childpid;
int childfdRead, childfdWrite; // file descriptors for childs
int parentfdsRead[numWorker], parentfdsWrite[numWorker]; // file descriptors for parent

// store the fifo filenames
char *childPipeNameRead[numWorker];
char *childPipeNameWrite[numWorker];

// helper string to construct fifo filenames
char *suffix = (char*)malloc(20*sizeof(char));
char *fifoname = (char*)malloc(20*sizeof(char));

for(i = 0; i < numWorker; i++){
    // Fifo filename structure read
    sprintf(fifoname, "%s", PATH);
    sprintf(suffix, "_childRead%d", i);
    childPipeNameRead[i] = strdup(strcat(fifoname, suffix));
    mkfifo(childPipeNameRead[i], 0666);

    // Fifo filename structure write
    sprintf(fifoname, "%s", PATH);
    sprintf(suffix, "_childWrite%d", i);
    childPipeNameWrite[i] = strdup(strcat(fifoname, suffix));
    mkfifo(childPipeNameWrite[i], 0666);

    childpid = fork();

    if(childpid < 0){
        perror("fork\n");
    }

    else if(childpid == 0){
        // Open read and write pipes on childs.
        if((childfdRead = open(childPipeNameRead[i], O_RDONLY | O_NONBLOCK)) < 0)
            perror("child pipe:");

        printf("Child with id %d opened pipe with name %s\n", getpid(), childPipeNameRead[i]);

        if((childfdWrite = open(childPipeNameWrite[i], O_WRONLY)) < 0)
            perror("child pipe:");

        printf("Child with id %d opened pipe with name %s\n", getpid(), childPipeNameWrite[i]);
        break;
    }
    else{
        // Open read and write pipes for each child in the parent process.
        if((parentfdsRead[i] = open(childPipeNameRead[i], O_RDONLY | O_NONBLOCK)) < 0)
            perror("parent pipe:");
        printf("Parent with id %d opened pipe with name %s\n", getpid(), childPipeNameRead[i]);

        if((parentfdsWrite[i] = open(childPipeNameWrite[i], O_WRONLY)) < 0)
            perror("parent pipe:");
        printf("Parent with id %d opened pipe with name %s\n", getpid(), childPipeNameWrite[i]);
    }
}

程序在 parent 和一个 child 打开他们的读取管道后挂起（parent 只打开其中一个）。这是正常行为吗？我期待它打开所有管道，因为我对 parent 和 child.

使用 O_RDONLY | O_NONBLOCK

Answer 1

问题是您在子进程和父进程中打开 childPipeNameRead[i] 进行读取。同样，您打开 childPipeNameWrite[i] 以在两个进程中写入。

您需要在其中一个过程中执行相反的操作。

Open() with O_WRONLY 块，即使我在另一端用 O_RDONLY open()

Open() with O_WRONLY blocks even though I open() with O_RDONLY on the other end

c

named-pipes