[linux]grep 查看前后文

这个可以man一下，

Context Line Control
       -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.

咋用？

grep -C 5 foo file  显示file文件中匹配foo字串那行以及上下5行

grep -B 5 foo file  显示foo及前5行
grep -A 5 foo file  显示foo及后5行