在命名管道上读取不阻塞

概述我有一个C代码从管道读取,然后应该阻止,但它从不阻止 int pipe_fd;int res;int open_mode = O_RDONLY;char buf[100];int bytes_read = 0;memset (buf, '\0', sizeof(buf));pipe_fd = open(FIFO_NAME, open_mode);if (access(FIFO_N 我有一个C代码从管道读取,然后应该阻止,但它从不阻止

int pipe_fd;int res;int open_mode = O_RDONLY;char buf[100];int bytes_read = 0;memset (buf,'
#!/bin/bashpipe=/tmp/pipeif [[ ! -p $pipe ]]; then    echo "Reader not running"    exit 1fiif [[ "" ]]; then     echo "some string" >$pipeelse     echo "q" >$pipefi
',sizeof(buf));pipe_fd = open(FIFO_name,open_mode);if (access(FIFO_name,F_OK) == -1){    res = mkfifo(FIFO_name,0777);    if (res != 0)    {            fprintf (stderr,"Could not create fifo %s\n",FIFO_name);              exit (EXIT_FAILURE);    }}for(;;){            do         {             res = read(pipe_fd,buf,sizeof(buf));        bytes_read += res;    }while (res > 0);    // process data then go back and block    ............}

它通过一些代码在一个bash脚本中发送一个简单的缓冲区,像这样’./test 1′

$mkfifo ./tmp1$cat < input > ./tmp1 &$cat < ./tmp1 > /dev/null

我在gdb中运行C代码程序,最初它会读取阻塞,但是一旦我调用bash脚本,C代码就不再阻塞,它会成功读取数据
缓冲区然后每次读取时都有0个字节读取,所以不知道为什么它不再阻塞. “一些字符串”数据在另一边正确接收.

我只需要坐在那里等待数据处理,然后回去等待更多

解决方法

I run the C code program in gdb and initially it does block on the read but as soon as i call the bash script the C code no longer blocks,it does successfully read the data from the buffer and then each time it reads there are 0 bytes read so not sure why its no longer blocking. The ‘some string’ data is correctly received at the other sIDe.

0表示EOF.只有当连接到它们的进程用于读取和写入时,FIFO才能被读取或写入.当没有更多的作者(你的shell脚本被终止)时,通过read()返回EOF就会通知读者.

FIFO的行为方式与shell管道逻辑兼容,例如：

如果read()不会返回EOF,则第二只猫会永久阻止.

I just need it to sit there waiting for data process it and then go back and wait for more

在C程序中,read()返回EOF后,必须重新打开()FIFO.

附：找到quite nice FIFO summary为你的.检查第二页上的表格.

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