blocks|key|200085|text|grep+'a\{n,m\}'+new表示从new中获取至少n个a，最多m个a。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|200086|例如，grep+'a\{2,3\}'+new将输出|200087|aaaa
aaa
aa|code-block|syntax|javascript|200088|最后一行不匹配，因为它只有一个a。|200089|对于a{n,\}'，省略m表示大于或等于n的任何数字。|200090|entityMap^0|0|J|W|1|12|1|0|3|J|0|0|F|1|0|2|7|C|1|K|1|0^^$0|@$1|2|3|4|5|6|7|S|8|@$9|T|A|U|B|C]|$9|V|A|W|B|C]|$9|X|A|Y|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|Z|8|@$9|10|A|11|B|C]]|D|@]|E|$]]|$1|H|3|I|5|J|7|12|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|13|8|@$9|14|A|15|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|16|8|@$9|17|A|18|B|C]|$9|19|A|1A|B|C]|$9|1B|A|1C|B|C]]|D|@]|E|$]]|$1|Q|3|-4|5|6|7|1D|8|@]|D|@]|E|$]]]|R|$]]

<code>grep 'a\{n,m\}' new</code> means grepping at least n number of <code>a</code> and at most m number of <code>a</code> from new. 
For example, <code>grep 'a\{2,3\}' new</code> will output

<pre><code>aaaa
aaa
aa
</code></pre>

the last line doesnot match because it only has ONE <code>a</code>. 
For <code>a{n,\}'</code> , omitting <code>m</code> means any number larger than or equal to <code>n</code>.

blocks|key|200188|text|来自man+grep|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|200189|+++Repetition
+++++++A+regular+expression+may+be++followed++by++one++of++several++repetition
+++++++operators:
+++++++?++++++The+preceding+item+is+optional+and+matched+at+most+once.
+++++++*++++++The+preceding+item+will+be+matched+zero+or+more+times.
+++++++%2B++++++The+preceding+item+will+be+matched+one+or+more+times.
+++++++{n}++++The+preceding+item+is+matched+exactly+n+times.
+++++++{n,}+++The+preceding+item+is+matched+n+or+more+times.
+++++++{n,m}++The++preceding++item++is++matched+at+least+n+times,+but+not+more
++++++++++++++than+m+times.|code-block|syntax|javascript|200190|由于前三个(或两个)+a，该示例grep+'a\{2,3\}'+new也与aaaa行匹配。这行的其余部分并不重要。|200191|如果您真的希望只匹配2到3个连续的a，您可以使用-o标志。但请注意，这将从包含aaaaa的一行输出aa和aaa。为了避免这种情况，您必须使用额外的信息，如示例换行%5E和$中的信息。|200192|顺便说一句。我建议使用-E标志(或同样的egrep+)，这样您就扩展了对正则表达式的支持。那么你就不需要转义括号了。|200193|对于输入|200194|aaaaa
aaaa
aaa
aa
a|200195|调用grep+-o+-E+'%5Ea{2,3}$'将给出以下输出：|200196|aaa
aa|200197|entityMap^0|2|8|0|0|B|1|G|J|11|4|0|H|1|O|2|13|5|1D|2|1G|3|29|1|2B|1|0|B|2|K|5|0|0|0|2|L|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@$9|11|A|12|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|13|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|14|8|@$9|15|A|16|B|C]|$9|17|A|18|B|C]|$9|19|A|1A|B|C]]|D|@]|E|$]]|$1|M|3|N|5|6|7|1B|8|@$9|1C|A|1D|B|C]|$9|1E|A|1F|B|C]|$9|1G|A|1H|B|C]|$9|1I|A|1J|B|C]|$9|1K|A|1L|B|C]|$9|1M|A|1N|B|C]|$9|1O|A|1P|B|C]]|D|@]|E|$]]|$1|O|3|P|5|6|7|1Q|8|@$9|1R|A|1S|B|C]|$9|1T|A|1U|B|C]]|D|@]|E|$]]|$1|Q|3|R|5|6|7|1V|8|@]|D|@]|E|$]]|$1|S|3|T|5|H|7|1W|8|@]|D|@]|E|$I|J]]|$1|U|3|V|5|6|7|1X|8|@$9|1Y|A|1Z|B|C]]|D|@]|E|$]]|$1|W|3|X|5|H|7|20|8|@]|D|@]|E|$I|J]]|$1|Y|3|-4|5|6|7|21|8|@]|D|@]|E|$]]]|Z|$]]

From <code>man grep</code>:

<pre><code> Repetition
 A regular expression may be followed by one of several repetition
 operators:
 ? The preceding item is optional and matched at most once.
 * The preceding item will be matched zero or more times.
 + The preceding item will be matched one or more times.
 {n} The preceding item is matched exactly n times.
 {n,} The preceding item is matched n or more times.
 {n,m} The preceding item is matched at least n times, but not more
 than m times.
</code></pre>

That example <code>grep 'a\{2,3\}' new</code> matches also the line with <code>aaaa</code> because of the first three (or 2) <code>a</code>. The rest of the line isn't important.

If you want that really only 2 or 3 consecutive <code>a</code> are matched, you could use the <code>-o</code> flag. But be aware that this would output <code>aa</code> and <code>aaa</code> from a line with <code>aaaaa</code>. To avoid this you have to use additional information, like in the example line breakings <code>^</code> and <code>$</code>.

Btw. I would suggest to use the <code>-E</code> flag (or <code>egrep</code> which is the same) so you have extended regex support. You don't have to escape the brackets then.

For input

<pre><code>aaaaa
aaaa
aaa
aa
a
</code></pre>

a call of <code>grep -o -E '^a{2,3}$'</code> will give the output:

<pre><code>aaa
aa
</code></pre>

I'm having a problem using grep with these options: <code>\{n\}</code> , <code>\{n,\}</code> and <code>\{n,m\}</code> . I have a file named "new" with this lines:

<pre><code>aaaa
aaa
aa
a
</code></pre>

When i use <code>grep 'a\{1\}' new</code> i get this output:

<pre><code>aaaa
aaa
aa
a
</code></pre>

So, basically, this command will show me the lines that include 1, or more, consecutive occurrences of the character "a" right?

Also, <code>grep 'a\{1,\} new</code> will do the same thing as <code>grep 'a\{1\}' new</code> ? Because i get the same output for both.

The last one, <code>\{n,m\}</code> , i cant really understand what it does.

I would really appreciate if anyone could help me out.

Linux Shell - Grep command

我在使用grep和以下选项时遇到了问题：\{n\}、\{n,\}和\{n,m\}。我有一个名为"new“的文件，其中有以下几行：aaaaaaaaaa当我使用grep 'a\{1\}' new时，我得到以下输出：aaaaaaaaaa所以，基本上，这个命令将显示包含1个或更多连续出现字符"a“的行，对吗？另外，grep '...

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