文件的read（）在Unix系统功能 [英] File read() function in Unix Systems

问题描述

下code。如果失败归因于信号中断重新启动阅读（）功能。在阅读（）继续从那里被打断了阅读。所以，如果阅读（）刚刚看完 EOF 字符前中断，会是什么回报，这多少字节读？

The code below restarts the read() function if it fails due to interruption by signal. The read() resumes its reading from where it was interrupted. So if read() is interrupted just before reading EOF character, what will it return that how many bytes it read?

int r_read(int fd, void *buf, int size)
{
   while((retval=read(fd,buf,size))==-1 && errno ==EINTR);
   return retval;
}  

问候。

推荐答案

这就是为什么读取的字节的数量应保持作为一个整体，以避免中断的问题。这也是有益的非阻塞I / O。

This is why the number of bytes read should be kept as a total, to avoid interrupt issues. It's also useful for non-blocking I/O.

{
    int ret = 0, nread;
    char *nbuf = (char *) buf;

    while ((nread = read(fd, nbuf, size)) != 0)
    {
        if (nread > 0)
            ret += nread, nbuf += nread, size -= nread;
        elif (errno != EINTR)
            break;
    }

    return ret;
}

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