关闭缓冲 [英] Turn off buffering

问题描述

哪里是按照本缓冲......？我怎么把它关掉？

Where is the buffer in this following ... and how do I turn it off?

我写出来到stdout在Python程序，像这样：

I am writing out to stdout in a python program like so:

for line in sys.stdin:
    print line

有一些缓冲的事情在这里：

There is some buffering going on here:

tail -f data.txt | grep -e APL | python -u Interpret.py

我尝试以下，以摆脱可能的缓冲......有没有运气：

I tried the following to shake off possible buffering ... with no luck:

• 如上使用-u标志使用Python调用


• 每个sys.stdout.write函数调用后sys.stdout.flush（）（）调用
  ......所有这些创建蟒蛇等待像一分钟，打印出来的前几行缓冲流。



• 使用以下修改的命令：

• as above using the -u flag with python invocation
• calling sys.stdout.flush() after each sys.stdout.write() call ... all of these create a buffered stream with python waiting something like a minute to print out the first few lines.

• used the following modified command:

stdbuf -o0尾-f的data.txt | stdbuf -o0 -i0的grep -e APL | stdbuf -i0 -o0蟒蛇-u国米pret.py

stdbuf -o0 tail -f data.txt | stdbuf -o0 -i0 grep -e APL | stdbuf -i0 -o0 python -u Interpret.py

要基准我的期望，我想：

To benchmark my expectations, I tried:

tail -f data.txt | grep -e APL 

这行产生了源源不断的......它肯定不是作为缓冲的python命令。

This produces a steady flow of lines ... it surely is not as buffered as the python command.

所以，我怎么关闭缓冲？
回答：原来有在管的两端缓冲

So, how do I turn off buffering? ANSWER: It turns out there is buffering on both ends of the pipe.

推荐答案

这个问题，我相信是的grep 缓冲它的输出。它这样做，当你管尾-f | grep的... | some_other_prog 。要获得的grep 每行冲洗一次，使用 - 行缓冲选项：

The problem, I believe is in grep buffering its output. It is doing that when you pipe tail -f | grep ... | some_other_prog. To get grep to flush once per line, use the --line-buffered option:

% tail -f data.txt | grep -e APL --line-buffered | test.py
APL

APL

APL

其中， test.py 是：

import sys
for line in sys.stdin:
    print(line)

（测试在Linux上，GNOME终端）。

(Tested on linux, gnome-terminal.)

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