perl命令：批量修改替换文件

需求以下：有nginx负载均衡配置文件，更新某几台服务器须要先注释掉前端机器，须要用脚本实现；

以前一直用sed进行替换，遇到一个高手用perl命令也能够实现，命令更简洁直观，能够实现一样的效果。

举例以下：

[root@localhost ~]# cat host.conf

upstream test_server {

server   192.168.169.36:80;

server   192.168.169.37:80;

server   192.168.169.38:80;

server   192.168.169.39:80;

server   192.168.169.50:80;

server   192.168.169.51:80;

server   192.168.169.52:80;

}

打印匹配的行

[root@localhost ~]# perl -ne 'print if /192.168.169.3/' host.conf

server   192.168.169.36:80;

server   192.168.169.37:80;

server   192.168.169.38:80;

server   192.168.169.39:80;

[root@localhost ~]# perl -ne 'print if /192.168.169.5/' host.conf

server   192.168.169.50:80;

server   192.168.169.51:80;

server   192.168.169.52:80;

perl命令：匹配192.168.169.3 网段的前面加#；

-i 写入到文件

[root@localhost ~]# perl -i -pe 's/(.*)/#$1/ if /192.168.169.3/' host.conf

执行结果以下：

[root@localhost ~]# cat host.conf

upstream test_server {

#server   192.168.169.36:80;

#server   192.168.169.37:80;

#server   192.168.169.38:80;

#server   192.168.169.39:80;

server   192.168.169.50:80;

server   192.168.169.51:80;

server   192.168.169.52:80;

}

同理，去掉#

[root@localhost ~]# perl -i -pe 's/#(.*)/$1/ if /192.168.169.3/' host.conf

[root@localhost ~]# cat host.conf

upstream test_server {

server   192.168.169.36:80;

server   192.168.169.37:80;

server   192.168.169.38:80;

server   192.168.169.39:80;

server   192.168.169.50:80;

server   192.168.169.51:80;

server   192.168.169.52:80;

}

匹配192.168.169. 网段的全部机器加#

[root@localhost ~]# perl -i -pe 's/(.*)/#$1/ if /192.168.169./' host.conf

[root@localhost ~]# cat host.conf

upstream test_server {

#server   192.168.169.36:80;

#server   192.168.169.37:80;

#server   192.168.169.38:80;

#server   192.168.169.39:80;

#server   192.168.169.50:80;

#server   192.168.169.51:80;

#server   192.168.169.52:80;

}

perl命令也支持相似sed的关键字替换

[root@localhost ~]#  perl -pe 's/server/master/ if /192.168.169.3/' host.conf

upstream test_server {

master   192.168.169.36:80;

master   192.168.169.37:80;

master   192.168.169.38:80;

master   192.168.169.39:80;

server   192.168.169.50:80;

server   192.168.169.51:80;

server   192.168.169.52:80;

}

问题来了，实际配置文件基本都是同一个网段的ip，若是匹配的话，会匹配到其余机器上面，问题就严重了，因此须要按指定行进行精确匹配；

[root@localhost ~]# cat host.conf

upstream test_server {

server   192.168.169.36:80;

server   192.168.169.37:80;

server   192.168.169.38:80;

server   192.168.169.39:80;

server   192.168.169.50:80;

server   192.168.169.51:80;

server   192.168.169.52:80;

}

perl命令，匹配指定的行

if 判断 $. 行数，与或关系进行匹配；

[root@localhost ~]#  perl -ne 'print if $.==2 ' host.conf

server   192.168.169.36:80;

[root@localhost ~]#  perl -ne 'print if $.==4 ' host.conf

server   192.168.169.38:80;

[root@localhost ~]#  perl -ne 'print if $.>=2 && $.<=5 ' host.conf

server   192.168.169.36:80;

server   192.168.169.37:80;

server   192.168.169.38:80;

server   192.168.169.39:80;

精确匹配，进行替换，大于等于第2行，小于等于第5行；

[root@localhost ~]# perl -pe 's/(.*)/#$1/ if $.>=2 && $.<=5' host.conf

upstream nav1_server {

#server   192.168.169.36:80;

#server   192.168.169.37:80;

#server   192.168.169.38:80;

#server   192.168.169.39:80;

server   192.168.169.50:80;

server   192.168.169.51:80;

server   192.168.169.52:80;

}

加-i 参数，将修改的操做写入到文件中；

[root@localhost ~]# perl -i -pe 's/(.*)/#$1/ if $.>=2 && $.<=5' host.conf