sed 命令及shell的if语句的运用实例

if [ -f /etc/syslog.conf ];     #判断文件是否存在
then
systest=`sed -n  ‘/^auth.info/p‘ /etc/syslog.conf`;    #匹配/etc/syslog.conf文件中是否有auto.info字符串，并返回字符串，systest变量接收。
if [ -n \"\$systest\" ];                                               #判断字符串是否存在
then
sed -e ‘s/^auth.info.*/auth.info        \\/var\\/adm\\/authlog/g‘ /etc/syslog.conf > config.tmp && mv config.tmp /etc/syslog.conf;  #存在则替换
else
awk ‘{print \$0} END{print \"auth.info        /var/adm/authlog\"}‘ /etc/syslog.conf > config.tmp && mv config.tmp /etc/syslog.conf; #不存在则在最后一行添加，solaris系统下不支持sed -i时使用。

sed -i ‘\$a auth.infos    /var/adm/authlogs‘ /etc/syslog.conf;      #不存在则在最后一行添加。 redhat，suse
fi;                                                                              #第一个内层判断结束
syserr=`sed -n  ‘/^*.err;auth.info/p‘ /etc/syslog.conf`;
if [ -n \"\$syserr\" ];
then
sed -e ‘s/^*.err;auth.info.*/*.err;auth.info        \@${loghost}/g‘ /etc/syslog.conf > config.tmp && mv config.tmp /etc/syslog.conf;
else
awk ‘{print \$0} END{print \"*.err;auth.info        \@${loghost}\"}‘ /etc/syslog.conf > config.tmp && mv config.tmp /etc/syslog.conf;
fi;                                                                         #第二个内层判断结束
fi;                                                                      
if [ -f /var/adm/authlog ];
then
echo \"\/var\/adm\/authlog exist.\";
else
touch /var/adm/authlog;                                #创建文件
chown root:system /var/adm/authlog;             #赋权
chmod 600 /var/adm/authlog;                         #赋权
echo \"create file /var/adm/authlog.\";
fi;";