计算文件中模式的出现次数（即使在同一行上） [英] Count number of occurrences of a pattern in a file (even on same line)

问题描述

当搜索文件中字符串的出现次数时，我通常使用：

  grep模式文件| wc -l 
  

但是，由于grep的工作原理，如何搜索字符串在文件中出现的次数，无论它们是在相同或不同的行上？

此外，如果我搜索正则表达式模式，而不是一个简单的字符串？

解决方案

要计算所有出现次数，请使用 -o 。尝试此操作：

  echo afoobarfoobar | grep -o foo |当然，wc -l 
  

和 man grep （：

更新

有些人建议只使用 grep -co foo 而不是 grep -o foo | wc -l <​​/ code>。

p>

这个快捷方式在所有情况下都无效。页面说明：

  -c打印匹配线条数
  

这些方法的区别如下：

1。

  $ echo afoobarfoobar | grep -oc foo 
 1 
  

一旦在行中找到 $ c> a {foo} barfoobar ）搜索停止，只有一行被检查并匹配，所以输出 1 code> -o 在此处被忽略，您可以改用 grep -c 。

2。

  $ echo afoobarfoobar | grep -o foo 
 foo 
 foo 
 
 $ echo afoobarfoobar | grep -o foo | wc -l 
 2 
  

在行中找到两个匹配（ a {foo} bar {foo} bar ），因为我们明确要求查找每个发生（ -o ） 。每次发生都打印在单独的行上， wc -l <​​/ code>只是计算输出中的行数。

When searching for number of occurrences of a string in a file, I generally use:

grep pattern file | wc -l

However, this only finds one occurrence per line, because of the way grep works. How can I search for the number of times a string appears in a file, regardless of whether they are on the same or different lines?

Also, what if I'm searching for a regex pattern, not a simple string? How can I count those, or, even better, print each match on a new line?

解决方案

To count all occurrences, use -o. Try this:

echo afoobarfoobar | grep -o foo | wc -l

And man grep of course (:

Update

Some suggest to use just grep -co foo instead of grep -o foo | wc -l.

Don't.

This shortcut won't work in all cases. Man page says:

-c print a count of matching lines

Difference in these approaches is illustrated below:

1.

$ echo afoobarfoobar | grep -oc foo
1

As soon as the match is found in the line (a{foo}barfoobar) the searching stops. Only one line was checked and it matched, so the output is 1. Actually -o is ignored here and you could just use grep -c instead.

2.

$ echo afoobarfoobar | grep -o foo
foo
foo

$ echo afoobarfoobar | grep -o foo | wc -l
2

Two matches are found in the line (a{foo}bar{foo}bar) because we explicitly asked to find every occurrence (-o). Every occurence is printed on a separate line, and wc -l just counts the number of lines in the output.

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