grep - 如何grep在特定模式上方和下方的线条

Question

我想搜索某个图案(比如条形线)，但还要在图案上方和下方(即 1 行)或图案上方和下方打印 2 行。

Foo  line
Bar line
Baz line

....

Foo1 line
Bar line
Baz1 line

....

Answer 1

使用 grep带参数-A和 -B表示行数 a A后和B在您想要围绕您的图案打印之前:

grep -A1 -B1 yourpattern file

An代表 n比赛“后”行。

Bm代表 m在比赛“之前”行。

如果两个数字相同，只需使用 -C :

grep -C1 yourpattern file

测试

$ cat file
Foo  line
Bar line
Baz line
hello
bye
hello
Foo1 line
Bar line
Baz1 line

让我们 grep :

$ grep -A1 -B1 Bar file
Foo  line
Bar line
Baz line
--
Foo1 line
Bar line
Baz1 line

要摆脱组分隔符，您可以使用 --no-group-separator :

$ grep --no-group-separator -A1 -B1 Bar file
Foo  line
Bar line
Baz line
Foo1 line
Bar line
Baz1 line

来自 man grep :

   -A NUM, --after-context=NUM
          Print NUM  lines  of  trailing  context  after  matching  lines.
          Places   a  line  containing  a  group  separator  (--)  between
          contiguous groups of matches.  With the  -o  or  --only-matching
          option, this has no effect and a warning is given.

   -B NUM, --before-context=NUM
          Print  NUM  lines  of  leading  context  before  matching lines.
          Places  a  line  containing  a  group  separator  (--)   between
          contiguous  groups  of  matches.  With the -o or --only-matching
          option, this has no effect and a warning is given.

   -C NUM, -NUM, --context=NUM
          Print NUM lines of output context.  Places a line  containing  a
          group separator (--) between contiguous groups of matches.  With
          the -o or --only-matching option,  this  has  no  effect  and  a
          warning is given.