为什么从长寿命FIFO读取时只返回readline(),而不返回readlines()或readlines()?

好的,我在Ubuntu中有一个FIFO文件。

with open(fifo_path) as f:
    while True:
        d = f.read()
        print(repr(d)) ## this is never called

这不起作用,我从来没有得到任何数据,它只是无限期地阻塞,即使有数据。

with open(fifo_path) as f:
    while True:
        d = f.readlines()
        print(repr(d)) ## this is also never called

这也不行。

with open(fifo_path) as f:
    while True:
        d = f.readline()
        print(repr(d)) ## only this is invoked

只有这样才有效。我得到了数据,它一直在读每一行。