while 循环语句

[root@localhost shell]# cat while-daemon01.sh 
#!/bin/sh
while true
do
    uptime >> /opt/uptime.sh
    sleep 2
done

[root@localhost shell]# bash  while-daemon01.sh
 

[root@localhost shell]# cat /opt/uptime.sh 
 15:25:02 up  5:21,  5 users,  load average: 0.00, 0.00, 0.00
 15:25:04 up  5:21,  5 users,  load average: 0.00, 0.00, 0.00
 15:25:06 up  5:21,  5 users,  load average: 0.00, 0.00, 0.00
 15:26:47 up  5:23,  5 users,  load average: 0.00, 0.00, 0.00
 15:26:49 up  5:23,  5 users,  load average: 0.00, 0.00, 0.00
 15:26:51 up  5:23,  5 users,  load average: 0.00, 0.00, 0.00
 15:26:53 up  5:23,  5 users,  load average: 0.00, 0.00, 0.00
 15:26:55 up  5:23,  5 users,  load average: 0.00, 0.00, 0.00
 15:26:57 up  5:23,  5 users,  load average: 0.00, 0.00, 0.00