如何在特定模式之上和之下的线条进行grep

我想搜索特定图案（比如小节线），而且打印的上方和下方（即1线）的图案或2行上方和下方的图案线条。

Foo  line
Bar line
Baz line

....

Foo1 line
Bar line
Baz1 line

....

---

使用带参数-A和-B grep指示要在您的模式周围打印的线A fter和B之前的数量a：

grep -A1 -B1 yourpattern file

An代表n “后”匹配线。

Bm代表比赛前的m条线。

如果两个数字都相同，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，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

从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.

---

grep是你的工具，但它可以用awk完成

awk '{a[NR]=$0} $0~s {f=NR} END {for (i=f-B;i<=f+A;i++) print a[i]}' B=1 A=2 s="Bar" file

注意，这也会发现一个命中。

或者用grep

grep -A2 -B1 "Bar" file

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