如何“grep"连续流? [英] How to 'grep' a continuous stream?
问题描述
可以在连续流上使用 grep
吗?
Is that possible to use grep
on a continuous stream?
我的意思是一种 tail -f
命令,但是在输出上带有 grep
以便只保留我感兴趣的行.
What I mean is sort of a tail -f <file>
command, but with grep
on the output in order to keep only the lines that interest me.
我试过 tail -f
但似乎grep
只能在tail
完成后执行,也就是说从不.
I've tried tail -f <file> | grep pattern
but it seems that grep
can only be executed once tail
finishes, that is to say never.
推荐答案
在使用 BSD grep (FreeBSD, Mac OS X etc.) 时打开 grep
的行缓冲模式
Turn on grep
's line buffering mode when using BSD grep (FreeBSD, Mac OS X etc.)
tail -f file | grep --line-buffered my_pattern
它看起来像不久前 --line-buffered
对 GNU grep(几乎在任何 Linux 上都使用过)无关紧要,因为它默认刷新(YMMV 用于其他类 Unix,例如SmartOS、AIX 或 QNX).但是,截至 2020 年 11 月,需要 --line-buffered
(至少在 openSUSE 中使用 GNU grep 3.5,但根据下面的评论似乎通常需要).
It looks like a while ago --line-buffered
didn't matter for GNU grep (used on pretty much any Linux) as it flushed by default (YMMV for other Unix-likes such as SmartOS, AIX or QNX). However, as of November 2020, --line-buffered
is needed (at least with GNU grep 3.5 in openSUSE, but it seems generally needed based on comments below).
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