-A和-B将起作用，-C n（对于n行上下文）或-n（对于n个上下文……只要n是1到9）也会起作用。

如果您经常搜索代码，AG银搜索器比grep更高效（即更快）。

使用-C选项显示上下文行。

Eg:

ag -C 3 "foo" myFile

line 1
line 2
line 3
line that has "foo"
line 5
line 6
line 7

ack使用与grep类似的参数，并接受-C。但它通常更适合于搜索代码。

我通常使用

grep searchstring file -C n # n for number of lines of context up and down

许多像grep这样的工具也有很棒的man文件。我发现自己经常参考grep的手册页，因为你可以用它做很多事情。

man grep

许多GNU工具也有一个信息页，除了手册页之外，它可能还有更多有用的信息。

info grep

Grep有一个名为Context Line Control的选项，您可以使用--Context，

| grep -C 5

or

| grep -5

应该会成功的

让我们用一个例子来理解。我们可以使用带有选项的grep：

-A 5  # this will give you 5 lines after searched string.
-B 5  # this will give you 5 lines before searched string.
-C 5  # this will give you 5 lines before & after searched string

实例File.txt包含6行，以下是操作。

[abc@xyz]~/% cat file.txt # print all file data
this is first line
this is 2nd line
this is 3rd line
this is 4th line
this is 5th line
this is 6th line

[abc@xyz]~% grep "3rd" file.txt # we are searching for keyword '3rd' in the file
this is 3rd line

[abc@xyz]~% grep -A 2 "3rd" file.txt # print 2 lines after finding the searched string
this is 3rd line
this is 4th line
this is 5th line

[abc@xyz]~% grep -B 2 "3rd" file.txt # Print 2 lines before the search string.
this is first line
this is 2nd line
this is 3rd line

[abc@xyz]~% grep -C 2 "3rd" file.txt # print 2 line before and 2 line after the searched string 
this is first line
this is 2nd line
this is 3rd line
this is 4th line
this is 5th line

记住选项的技巧：选项：

-一个 -> 之后的平均值-B级 -> B表示之前。-c类 -> 介于两者之间