我将ping结果保存到文件中，但有时不显示日期。我尝试了一些ping，发现收到0个数据包时并不总是显示日期。我在这里复制的第一个ping有0个收到的数据包并显示日期，最后一个没有。
[jsmith@localhost ~]$ ping 192.168.100.2 -D -c 1 -I eth0
PING 192.168.100.2 (192.168.100.2) from 192.168.100.3 eth0: 56(84) bytes of data.
[1424572632.214329] From 192.168.100.3 icmp_seq=1 Destination Host Unreachable
--- 192.168.100.2 ping statistics ---
1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms
[jsmith@localhost ~]$ ping 192.168.100.2 -D -c 1 -I eth0
PING 192.168.100.2 (192.168.100.2) from 192.168.100.3 eth0: 56(84) bytes of data.
[1424572638.603008] 64 bytes from 192.168.100.2: icmp_seq=1 ttl=64 time=0.374 ms
--- 192.168.100.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.374/0.374/0.374/0.000 ms
[jsmith@localhost ~]$ ping 192.168.100.2 -D -c 1 -I eth0
PING 192.168.100.2 (192.168.100.2) from 192.168.100.3 eth0: 56(84) bytes of data.
[1424572645.153724] 64 bytes from 192.168.100.2: icmp_seq=1 ttl=64 time=0.315 ms
--- 192.168.100.2 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.315/0.315/0.315/0.000 ms
[jsmith@localhost ~]$ ping 192.168.100.2 -D -c 1 -I eth0
PING 192.168.100.2 (192.168.100.2) from 192.168.100.3 eth0: 56(84) bytes of data.
--- 192.168.100.2 ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms
有什么问题？