的grep管道不与尾巴工作吗？ [英] Piping of grep is not working with tail?

问题描述

我想通过检查日志来调试一个场景，这里是我的命令

I am trying to debug one scenario by checking the logs, here is my command

tail -f eclipse.log | grep 'enimation' | grep  -i 'tap'

基本上，我想的是，所有行的，我打印线，在它enimation，那么所有的动画，我希望看到的动画在它的龙头。

Basically what I am trying to to is that, of all of the line, I am printing lines with enimation in it, then of all of the animation, I want to see the animation with "tap" in it.

下面是它被返回空的结果sammple数据

Here is the sammple data for which it is returning empty results

*******enimation error*********TapExpand
*******enimation error*********TapShrink

这是返回空的结果。

而如果我运行此命令

 tail -f eclipse.log | grep  -i 'enimation.*tap'

它返回正确的结果。可有人请给我解释一下，什么是上面的两个命令，以及为什么没有在结果的差异之间的区别。他们似乎都等同于我。

it returns correct results. Can someone please explain to me, what is the difference between the above two command and why there is a discrepancy in the results. They both seem identical to me.

推荐答案

的grep 正在缓冲它的输出。告诉GNU的grep吐出输出的行由行您需要使用 - 在行缓冲选项grep的，使其工作：

grep is buffering it's output. To tell GNU grep to spit out output line-by-line you need to use --line-buffered option in grep to make it work:

tail -f eclipse.log | grep --line-buffered 'enimation' | grep --line-buffered -i 'tap'

按的grep人：

--line-buffered
    Force output to be line buffered.  By default, output is line buffered when standard
    output is a terminal and block buffered otherwise.

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