计算一个文件中模式的出现次数(甚至在同一行中)

在搜索文件中字符串的出现次数时，我通常使用:

grep pattern file | wc -l

但是，由于 grep 的工作方式，每行只能找到一个匹配项。如何搜索字符串在文件中出现的次数，而不管它们是在同一行上还是在不同的行上？

另外，如果我搜索的是正则表达式模式，而不是简单的字符串，该怎么办？如何计算这些数字，或者更好的方法是将每个匹配项打印到一个新行上？

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小开

Hack grep's color function, and count how many color tags it prints out:

echo -e "a\nb  b b\nc\ndef\nb e brb\nr" \
| GREP_COLOR="033" grep --color=always  b \
| perl -e 'undef $/; $_=<>; s/\n//g; s/\x1b\x5b\x30\x33\x33/\n/g; print $_' \
| wc -l
小开
最佳答案

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.

小开

A belated post:
Use the search regex pattern as a Record Separator (RS) in awk
This allows your regex to span \n-delimited lines (if you need it). 

printf 'X \n moo X\n XX\n' |
awk -vRS='X[^X]*X' 'END{print (NR<2?0:NR-1)}'
小开

Try this:

grep "string to search for" FileNameToSearch | cut -d ":" -f 4 | sort -n | uniq -c

Sample:

grep "SMTP connect from unknown" maillog | cut -d ":" -f 4 | sort -n | uniq -c
6  SMTP connect from unknown [188.190.118.90]
54  SMTP connect from unknown [62.193.131.114]
3  SMTP connect from unknown [91.222.51.253]
小开

Ripgrep, which is a fast alternative to grep, has just introduced the --count-matches flag allowing counting each match in version 0.9 (I'm using the above example to stay consistent):

> echo afoobarfoobar | rg --count foo
1
> echo afoobarfoobar | rg --count-matches foo
2

As asked by OP, ripgrep allows for regex pattern as well (--regexp <PATTERN>). Also it can print each (line) match on a separate line:

> echo -e "line1foo\nline2afoobarfoobar" | rg foo
line1foo
line2afoobarfoobar

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