perl命令：批量修改替换文件
需求如下：有nginx负载均衡配置文件，更新某几台服务器需要先注释掉前端机器，需要用脚本实现；之前一直用sed进行替换，遇到一个高手用perl命令也可以实现，命令更简洁直观，可以实现同样的效果。
举例如下：
# 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
# 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;
# 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
# perl -i -pe 's/(.*)/#$1/ if /192.168.169.3/' host.conf
执行结果如下：
# 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#
# perl -i -pe 's/#(.*)/$1/ if /192.168.169.3/' host.conf
# 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. 网段的所有机器加#
# perl -i -pe 's/(.*)/#$1/ if /192.168.169./' host.conf
# 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命令也支持类似sed的关键字替换
#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，如果匹配的话，会匹配到其他机器上面，问题就严重了，所以需要按指定行进行精确匹配；
# 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；
#perl -ne 'print if $.==2 ' host.conf
server 192.168.169.36:80;
#perl -ne 'print if $.==4 ' host.conf
server 192.168.169.38:80;
#perl -ne 'print if $.>=2 && $.=2 && $.=2 && $.
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