Ping 的 Bash 退出状态代码
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Bash Exit Status codes for Ping
提问by NATHAN C
I am working on a small script that checks if a host is up or down.
我正在编写一个小脚本，用于检查主机是启动还是关闭。
until [ "$STATUS" -eq "0" ]
do
ping -c 1 192.168.0.3
echo The host is down
STATUS=`echo $?`
done
It is supposed to change the status to 0 if it pings a host that is up and exit the until loop. But it doesnt. Even if I echo out the value of $? the value is always zero.
如果它 ping 一个正在运行的主机并退出直到循环，它应该将状态更改为 0。但它没有。即使我回显出$的价值？该值始终为零。
Can anyone help me figure this out please? :)
任何人都可以帮我解决这个问题吗？:)
Thanks in advance
提前致谢
回答by iamauser
You have echo The host is downafter pingcommand. So $?takes the exit status of the echocommand not the pingcommand.
你有echo The host is down后ping命令。所以$?采用echo命令的退出状态而不是ping命令。
ping -c 1 192.168.0.3
STATUS=$?
if [ $STATUS -ne 0 ]; then
echo "The host is down"
fi
回答by konsolebox
You placed echo after saving the status that's why you always get 0:
您在保存状态后放置了 echo，这就是为什么您总是得到 0：
ping -c 1 192.168.0.3
echo The host is down ## Always changes $? to 0
STATUS=`echo $?`
One better way to do it could be:
一种更好的方法可能是：
until ping -c 1 192.168.0.3; do
echo "The host is down"
done
Longer version:
更长的版本：
until ping -c 1 192.168.0.3; STATUS=$?; [ "$STATUS" -eq "0" ]; do
echo "The host is down"
done
