grep ABC之行匹配

grep和awk、sed一样，是linux最常用的几个工具之一。grep自行带的ABC三个参数在行匹配方面，非常有用。其中A(after)用于输出匹配行的后N行，B(before)用于输出匹配行的前N行，C(center)用于输出匹配行的前后各N行。具体示例如下：

  1 uwsgi_param  QUERY_STRING       $query_string;
  2 uwsgi_param  REQUEST_METHOD     $request_method;
  3 uwsgi_param  CONTENT_TYPE       $content_type;
  4 uwsgi_param  CONTENT_LENGTH     $content_length;
  5 uwsgi_param  REQUEST_URI        $request_uri;
  6 uwsgi_param  PATH_INFO          $document_uri;
  7 uwsgi_param  DOCUMENT_ROOT      $document_root;
  8 uwsgi_param  SERVER_PROTOCOL    $server_protocol;
  9 uwsgi_param  HTTPS              $https if_not_empty;
 10 uwsgi_param  REMOTE_ADDR        $remote_addr;
 11 uwsgi_param  REMOTE_PORT        $remote_port;
 12 uwsgi_param  SERVER_PORT        $server_port;
 13 uwsgi_param  SERVER_NAME        $server_name;

具体我有一文本内容如上所示，grep匹配后的结果如下所示：

A参数：

[root@api conf]# grep -A 3 'HTTPS' test.txt
  9 uwsgi_param  HTTPS              $https if_not_empty;
 10 uwsgi_param  REMOTE_ADDR        $remote_addr;
 11 uwsgi_param  REMOTE_PORT        $remote_port;
 12 uwsgi_param  SERVER_PORT        $server_port;

B参数：

[root@api conf]# grep -B 3 'HTTPS' test.txt
  6 uwsgi_param  PATH_INFO          $document_uri;
  7 uwsgi_param  DOCUMENT_ROOT      $document_root;
  8 uwsgi_param  SERVER_PROTOCOL    $server_protocol;
  9 uwsgi_param  HTTPS              $https if_not_empty;

C参数：

[root@api conf]# grep -C 3 'HTTPS' test.txt
  6 uwsgi_param  PATH_INFO          $document_uri;
  7 uwsgi_param  DOCUMENT_ROOT      $document_root;
  8 uwsgi_param  SERVER_PROTOCOL    $server_protocol;
  9 uwsgi_param  HTTPS              $https if_not_empty;
 10 uwsgi_param  REMOTE_ADDR        $remote_addr;
 11 uwsgi_param  REMOTE_PORT        $remote_port;
 12 uwsgi_param  SERVER_PORT        $server_port;

使用C参数时，和grep按如下命令的执行结果相同：

[root@api conf]# grep -3 'HTTPS' test.txt
  6 uwsgi_param  PATH_INFO          $document_uri;
  7 uwsgi_param  DOCUMENT_ROOT      $document_root;
  8 uwsgi_param  SERVER_PROTOCOL    $server_protocol;
  9 uwsgi_param  HTTPS              $https if_not_empty;
 10 uwsgi_param  REMOTE_ADDR        $remote_addr;
 11 uwsgi_param  REMOTE_PORT        $remote_port;
 12 uwsgi_param  SERVER_PORT        $server_port;