How do I print the line number with each matched line?

2018-06-27 13:41:24

I want to extract some lines from a file and output the line number in front of each extracted line.

For example, with the following input in a file named file

This is line1
This is line2
This is test1
This is test2
This is linex

After I execute the perl command

perl -ne 'if (/test/) {print "$_"}' file

I obtain this:

This is test1
This is test2

But I want to insert the line number at the beginning of the line.

line3: This is test1
line4: This is test2

How can I insert the line number?

The variable that keep the line number is $. , so use it interpolated in the double quotes of the print function:

perl -ne 'if (/test/) {print "line$.: $_"}' file

It yields:

line3: This is test1
line4: This is test2

其实我认为使用grep更容易：

grep -n test file

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