如何限制grep返回的结果的数量?

I would like to say 10 lines max from grep.

我想说grep的最多10行。

I don't want my computer to work hard. I want it to stop after 10 results found by grep. Is it possible?

我不想让我的电脑工作太辛苦。我希望在grep发现10个结果后停止。是可能的吗?

4 个解决方案

#1

174

The -m option is probably what you're looking for:

m选项可能就是你要找的:

grep -m 10 PATTERN [FILE]

From man grep,

从男人grep,

 -m NUM, --max-count=NUM
          Stop reading a file after NUM matching lines.  If the  input  is
          standard  input  from a regular file, and NUM matching lines are
          output, grep ensures that the standard input  is  positioned  to
          just  after the last matching line before exiting, regardless of
          the presence of trailing context lines.  This enables a  calling
          process  to resume a search.

Note: grep stops reading the file once the specified number of matches have been found!

注意:一旦找到指定的匹配数，grep将停止读取文件!

#2

Another option is just using head:

另一个选择是使用head:

grep ...parameters... yourfile | head

This won't require searching the entire file - it will stop when the first ten matching lines are found. Another advantage with this approach is that will return no more than 10 lines even if you are using grep with the -o option.

这并不需要搜索整个文件——当找到前10行匹配的行时，它将停止。这种方法的另一个优点是即使使用grep和-o选项，也不会返回超过10行。

For example if the file contains the following lines:

例如，如果文件包含以下行:

112233
223344
123123

Then this is the difference in the output:

这是输出的差值

$ grep -o '1.' yourfile | head -n2
11
12

$ grep -m2 -o '1.'
11
12
12

Using head returns only 2 results as desired, whereas -m2 returns 3.

使用head只返回2个结果，而-m2返回3个结果。

#3

Awk approach:

Awk的方法:

awk '/pattern/{print; count++; if (count==10) exit}' file

#4

Using tail:

使用尾:

#dmesg 
...
...
...
[132059.017752] cfg80211:   (57240000 KHz - 65880000 KHz @ 2160000 KHz), (N/A, 4000 mBm)
[132116.566238] cfg80211: Calling CRDA to update world regulatory domain
[132116.568939] cfg80211: World regulatory domain updated:
[132116.568942] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[132116.568944] cfg80211:   (2402000 KHz - 2472000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[132116.568945] cfg80211:   (2457000 KHz - 2482000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[132116.568947] cfg80211:   (2474000 KHz - 2494000 KHz @ 20000 KHz), (300 mBi, 2000 mBm)
[132116.568948] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[132116.568949] cfg80211:   (5735000 KHz - 5835000 KHz @ 40000 KHz), (300 mBi, 2000 mBm)
[132120.288218] cfg80211: Calling CRDA for country: GB
[132120.291143] cfg80211: Regulatory domain changed to country: GB
[132120.291146] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[132120.291148] cfg80211:   (2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[132120.291150] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[132120.291152] cfg80211:   (5250000 KHz - 5330000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[132120.291153] cfg80211:   (5490000 KHz - 5710000 KHz @ 40000 KHz), (N/A, 2700 mBm)
[132120.291155] cfg80211:   (57240000 KHz - 65880000 KHz @ 2160000 KHz), (N/A, 4000 mBm)
alex@ubuntu:~/bugs/navencrypt/dev-tools$ dmesg | grep cfg8021 | head 2
head: cannot open ‘2’ for reading: No such file or directory
alex@ubuntu:~/bugs/navencrypt/dev-tools$ dmesg | grep cfg8021 | tail -2
[132120.291153] cfg80211:   (5490000 KHz - 5710000 KHz @ 40000 KHz), (N/A, 2700 mBm)
[132120.291155] cfg80211:   (57240000 KHz - 65880000 KHz @ 2160000 KHz), (N/A, 4000 mBm)
alex@ubuntu:~/bugs/navencrypt/dev-tools$ dmesg | grep cfg8021 | tail -5
[132120.291148] cfg80211:   (2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[132120.291150] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[132120.291152] cfg80211:   (5250000 KHz - 5330000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[132120.291153] cfg80211:   (5490000 KHz - 5710000 KHz @ 40000 KHz), (N/A, 2700 mBm)
[132120.291155] cfg80211:   (57240000 KHz - 65880000 KHz @ 2160000 KHz), (N/A, 4000 mBm)
alex@ubuntu:~/bugs/navencrypt/dev-tools$ dmesg | grep cfg8021 | tail -6
[132120.291146] cfg80211:   (start_freq - end_freq @ bandwidth), (max_antenna_gain, max_eirp)
[132120.291148] cfg80211:   (2402000 KHz - 2482000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[132120.291150] cfg80211:   (5170000 KHz - 5250000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[132120.291152] cfg80211:   (5250000 KHz - 5330000 KHz @ 40000 KHz), (N/A, 2000 mBm)
[132120.291153] cfg80211:   (5490000 KHz - 5710000 KHz @ 40000 KHz), (N/A, 2700 mBm)
[132120.291155] cfg80211:   (57240000 KHz - 65880000 KHz @ 2160000 KHz), (N/A, 4000 mBm)
alex@ubuntu:~/bugs/navencrypt/dev-tools$

#1

174