使用sed在源文件上直接替换某一行的内容，只替换第一次找到的那行
sed -i 's/^mysqld_pid_file_path=.*$/mysqld_pid_file_path=\/data\/mysql\/run\/mysqld.pid/' /etc/init.d/mysqld
sed -i "s/^lockdir=.*$/lockdir='\/data\/mysql\/lock\/subsys'/" /etc/init.d/mysqld
sed -i 's/^mysqld_pid_file_path=.*$/mysqld_pid_file_path=\/data\/mysql\/run\/mysqld.pid/' /etc/init.d/mysqld
sed -i "s/^lockdir=.*$/lockdir='\/data\/mysql\/lock\/subsys'/" /etc/init.d/mysqld
