为什么我从grep -oc“foo”中得到不同的答案？ file和grep -o“foo”文件| wc -l？哪个是对的？ [英] Why am I getting different answers from grep -oc "foo" file and grep -o "foo" file | wc -l ? Which is correct?

问题描述

这个问题说明了这一切......我试图在一个大文件中找到特定
字符串的出现次数。
答案是相似的......就像50 000左右的管道和49 000奇数只是简单的grep - oc ...

任何人都可以解释为什么我得到不同的答案，哪一个会是正确？

感谢您的帮助。

解决方案

c $ c> - 只匹配（ -o ）mode grep有时会为单个匹配行输出多行。

  alex @ yuzu：〜$ echo -efoo\\\
bar\\\
baz
 foo 
 bar 
 baz 
 
 alex @ yuzu：〜$ echo -efoo\\\
bar\\\
baz| grep -oo 
o 
o 
  

但是 - 计数（ -c ）它会计算匹配行数。

  alex @ yuzu：〜$ echo -efoo\\\
bar\\\
baz| grep -oc o 
 1 
  

所以 grep -o o | wc -l <​​/ code>会计算所有匹配项，即使在一行中有多个匹配项。

The question says it all really... I am trying to find the number of occurences of specific strings in a large file.
The answers are similar.... like 50 000 or so with the pipe and 49 000 odd with just the plain grep - oc...

Can anyone explain why I am getting different answers, and which one would be correct?

Thanks for the help.

解决方案

In --only-matching (-o) mode grep will sometimes output multiple lines for a single matching line.

alex@yuzu:~$ echo -e "foo\nbar\nbaz"
foo
bar
baz

alex@yuzu:~$ echo -e "foo\nbar\nbaz" | grep -o o  
o
o

But with --count (-c) it will count the number of matching lines.

alex@yuzu:~$ echo -e "foo\nbar\nbaz" | grep -oc o
1

So grep -o o | wc -l is counting all the matches, even if there is more than one match in a single line.

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