UNIX grep命令（grep -v grep） [英] UNIX grep command (grep -v grep)

问题描述

grep -v grep

这是什么意思？我知道 -v 开关将选择所有不匹配的行。但为什么第二个 grep ？

这是完整的命令：

  ps -ef | grep rsync -avz \ 
 | grep oradata $ {DAY} _ [0-1] [0-9] \ 
 | grep -v grep \ 
 | awk'{print $ 2}'| wc -l 
  

解决方案

grep 与 ps -ef 一起使用时，还会输出用于过滤<$的输出的 grep c $ c> ps -ef 。

grep -v grep 表示不包含 grep 用于在命令输出中进行过滤。

您也可以通过使用来避免 grep code> regex 模式。
例如，在下面的例子中，您将不需要 grep -v grep 来避免 grep 在输出中：

  ps -ef | grep [r] sync 
  

下面是另一个示例，显示不同的命令及其输出，注意第一个 grep 也在输出中，而最后两个 grep 不会打印在输出中：

  $ ps -ef | grep ipython 
 501 18055 18031 0 12:44 ttys000 0：00.00 / bin / bash /Users/amit/anaconda/bin/python.app/Users/amit/anaconda/bin/ipython notebook --profile = ocean 
 501 18056 18055 0 12:44 ttys000 0：00.85 /Users/amit/anaconda/python.app/Contents/MacOS/python/ Users / amit / anaconda / bin / ipython notebook --profile = ocean 
 501 18067 18031 0 12:44 ttys000 0：00.00 grep ipython 
 
 $ ps -ef | grep ipython | grep -v grep 
 501 18055 18031 0 12:44 ttys000 0：00.00 / bin / bash /Users/amit/anaconda/bin/python.app / Users / amit / anaconda / bin / ipython notebook --profile =海洋
 501 18056 18055 0 12:44 ttys000 0：00.85 /Users/amit/anaconda/python.app/Contents/MacOS/python/Users/amit/anaconda/bin/ipython notebook --profile = ocean 
 
 $ ps -ef | grep [i] python 
 501 18055 18031 0 12:44 ttys000 0：00.00 / bin / bash /Users/amit/anaconda/bin/python.app/Users/amit/anaconda/bin/ipython notebook --profile = ocean 
 501 18056 18055 0 12:44 ttys000 0：00.85 /Users/amit/anaconda/python.app/Contents/MacOS/python/Users/amit/anaconda/bin/ipython notebook --profile = ocean 
  

I was going through something and found this which I could not understand,

grep -v grep

What does this signify? I know that -v switch will select all the lines that do not match. But why the second grep?

This is the full command:

ps -ef | grep rsync -avz \
| grep oradata${DAY}_[0-1][0-9] \
| grep -v grep \
| awk '{print $2}' | wc -l

解决方案

grep when used with ps -ef also outputs the grep used for filtering the output of ps -ef.

grep -v grep means that do not include the grep used for filtering in the command output.

You can also avoid grep in the results by using a regex pattern. For example, in the following example you won't need a grep -v grep to avoid grep in the output:

ps -ef | grep [r]sync

Here's another example, showing different commands and their output, notice the first one where grep is also in the output whereas in the last two grep is not printed in the output:

$ ps -ef | grep ipython
  501 18055 18031   0 12:44AM ttys000    0:00.00 /bin/bash /Users/amit/anaconda/bin/python.app /Users/amit/anaconda/bin/ipython notebook --profile=ocean
  501 18056 18055   0 12:44AM ttys000    0:00.85 /Users/amit/anaconda/python.app/Contents/MacOS/python /Users/amit/anaconda/bin/ipython notebook --profile=ocean
  501 18067 18031   0 12:44AM ttys000    0:00.00 grep ipython

$ ps -ef | grep ipython | grep -v grep
  501 18055 18031   0 12:44AM ttys000    0:00.00 /bin/bash /Users/amit/anaconda/bin/python.app /Users/amit/anaconda/bin/ipython notebook --profile=ocean
  501 18056 18055   0 12:44AM ttys000    0:00.85 /Users/amit/anaconda/python.app/Contents/MacOS/python /Users/amit/anaconda/bin/ipython notebook --profile=ocean

$ ps -ef | grep [i]python
  501 18055 18031   0 12:44AM ttys000    0:00.00 /bin/bash /Users/amit/anaconda/bin/python.app /Users/amit/anaconda/bin/ipython notebook --profile=ocean
  501 18056 18055   0 12:44AM ttys000    0:00.85 /Users/amit/anaconda/python.app/Contents/MacOS/python /Users/amit/anaconda/bin/ipython notebook --profile=ocean

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