blocks|key|1909574|text|使用超时选项-t|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1909575|ping+-q+-t+5+-w1+-c1+8.8.8.8+t|code-block|syntax|javascript|1909576|entityMap^0|6|2|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Use the timeout option <code>-t</code>:

<pre><code>ping -q -t 5 -w1 -c1 8.8.8.8 t
</code></pre>

blocks|key|1909578|text|使用wget：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1909579|#!/bin/bash

wget+-q+--tries=10+--timeout=20+--spider+http://google.com
if+[[+$?+-eq+0+]];+then
++++++++echo+"Online"
else
++++++++echo+"Offline"
fi|code-block|syntax|javascript|1909580|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Using wget:

<pre><code>#!/bin/bash

wget -q --tries=10 --timeout=20 --spider http://google.com
if [[ $? -eq 0 ]]; then
 echo "Online"
else
 echo "Offline"
fi
</code></pre>

blocks|key|1909602|text|安装fping：>比ping问题更少。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1909603|fping+google.com+%7C+grep+alive|code-block|syntax|javascript|1909604|例如，使用如下命令：|1909605|#!/bin/bash

itest=$(fping+google.com+%7C+grep+alive)

while+[+"$itest"+==+""+]
++++++++do
++++++++sleep+5
++++++++itest=$(fping+google.com+%7C+grep+alive)
done
echo+now+online|1909606|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Install fping: &gt; fewer problems than ping.
<pre><code>fping google.com | grep alive
</code></pre>
To use, for example, like:
<pre><code>#!/bin/bash

itest=$(fping google.com | grep alive)

while [ &quot;$itest&quot; == &quot;&quot; ]
 do
 sleep 5
 itest=$(fping google.com | grep alive)
done
echo now online
</code></pre>

blocks|key|1909683|text|使用上面的例子。我编写了这个脚本来记录您的连接状态：https://gist.github.com/cganterh/ffc2fffa8263857cbece|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1909684|首先，将以下代码保存到一个name.sh文件中。|style|CODE|1909685|#!/bin/bash

while+true
do
++++wget+-q+--tries=10+--timeout=20+-O+-+http://google.com+>+/dev/null
++++if+[[+$?+-eq+0+]];+then
++++++++echo+$(date)+"1"+%7C+tee+-a+log.csv
++++else
++++++++echo+$(date)+"0"+%7C+tee+-a+log.csv
++++fi
++++sleep+5
done|code-block|syntax|javascript|1909686|然后在终端执行name.sh文件，查看同一文件夹下log.csv中的日志状态信息。|1909687|entityMap|0|LINK|mutability|MUTABLE|url|https://gist.github.com/cganterh/ffc2fffa8263857cbece^0|Q|1H|0|0|D|7|0|0|7|7|P|7|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]]|C|$]]|$1|D|3|E|5|6|7|10|8|@$A|11|B|12|F|G]]|9|@]|C|$]]|$1|H|3|I|5|J|7|13|8|@]|9|@]|C|$K|L]]|$1|M|3|N|5|6|7|14|8|@$A|15|B|16|F|G]|$A|17|B|18|F|G]]|9|@]|C|$]]|$1|O|3|-4|5|6|7|19|8|@]|9|@]|C|$]]]|P|$Q|$5|R|S|T|C|$U|V]]]]

Using the example above. I wrote this script to log the state of your connection:
<a href="https://gist.github.com/cganterh/ffc2fffa8263857cbece" rel="nofollow noreferrer">https://gist.github.com/cganterh/ffc2fffa8263857cbece</a>
First, save the following code into a <code>name.sh</code> file.
<pre><code>#!/bin/bash

while true
do
 wget -q --tries=10 --timeout=20 -O - http://google.com &gt; /dev/null
 if [[ $? -eq 0 ]]; then
 echo $(date) &quot;1&quot; | tee -a log.csv
 else
 echo $(date) &quot;0&quot; | tee -a log.csv
 fi
 sleep 5
done
</code></pre>
Then, execute <code>name.sh</code> file in terminal, and then check the log state information in <code>log.csv</code> of the same folder.

blocks|key|1696227|text|如果学校真的关闭了路由器，而不是将所有流量重定向到“你为什么不在床上”的页面，那么就不需要下载整个网页或发送HTTP报头。你所要做的就是建立一个连接并检查是否有人在监听。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1696228|nc+-z+8.8.8.8+53|code-block|syntax|javascript|1696229|这将输出“连接到8.8.8.8端口53+tcp/域成功！”如果有人在监听，则返回值0。|1696230|如果您想在shell脚本中使用它：|1696231|nc+-z+8.8.8.8+53++>/dev/null+2>&1
online=$?
if+[+$online+-eq+0+];+then
++++echo+"Online"
else
++++echo+"Offline"
fi|1696232|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|6|7|R|8|@]|9|@]|A|$]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

If the school actually turns off their router instead of redirecting all traffic to a "why aren't you in bed" page, then there's no need to download an entire web page or send HTTP headers. All you have to do is just make a connection and check if someone's listening.

<pre><code>nc -z 8.8.8.8 53
</code></pre>

This will output "Connection to 8.8.8.8 port 53 [tcp/domain] succeeded!" and return a value of 0 if someone's listening. 

If you want to use it in a shell script:

<pre><code>nc -z 8.8.8.8 53 &gt;/dev/null 2&gt;&amp;1
online=$?
if [ $online -eq 0 ]; then
 echo "Online"
else
 echo "Offline"
fi
</code></pre>

blocks|key|1696317|text|使用：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1696318|#!/bin/bash

INTERNET_STATUS="UNKNOWN"
TIMESTAMP=`date+%2B%25s`
while+[+1+]
+do
++++ping+-c+1+-W+0.7+8.8.4.4+>+/dev/null+2>&1
++++if+[+$?+-eq+0+]+;+then
++++++++if+[+"$INTERNET_STATUS"+!=+"UP"+];+then
++++++++++++echo+"UP+++`date+%2B%25Y-%25m-%25dT%25H:%25M:%25S%25Z`+$((`date+%2B%25s`-$TIMESTAMP))";
++++++++++++INTERNET_STATUS="UP"
++++++++fi
++++else
++++++++if+[+"$INTERNET_STATUS"+=+"UP"+];+then
++++++++++++echo+"DOWN+`date+%2B%25Y-%25m-%25dT%25H:%25M:%25S%25Z`+$((`date+%2B%25s`-$TIMESTAMP))";
++++++++++++INTERNET_STATUS="DOWN"
++++++++fi
++++fi
++++sleep+1
+done;|code-block|syntax|javascript|1696319|输出将产生类似如下的结果：|1696320|./internet_check.sh

UP+++2016-05-10T23:23:06BST+4
DOWN+2016-05-10T23:23:25BST+19
UP+++2016-05-10T23:23:32BST+7|1696321|行尾的数字表示前一状态的持续时间，即19次上升，7秒下降。|1696322|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Use:
<pre><code>#!/bin/bash

INTERNET_STATUS=&quot;UNKNOWN&quot;
TIMESTAMP=`date +%s`
while [ 1 ]
 do
 ping -c 1 -W 0.7 8.8.4.4 &gt; /dev/null 2&gt;&amp;1
 if [ $? -eq 0 ] ; then
 if [ &quot;$INTERNET_STATUS&quot; != &quot;UP&quot; ]; then
 echo &quot;UP `date +%Y-%m-%dT%H:%M:%S%Z` $((`date +%s`-$TIMESTAMP))&quot;;
 INTERNET_STATUS=&quot;UP&quot;
 fi
 else
 if [ &quot;$INTERNET_STATUS&quot; = &quot;UP&quot; ]; then
 echo &quot;DOWN `date +%Y-%m-%dT%H:%M:%S%Z` $((`date +%s`-$TIMESTAMP))&quot;;
 INTERNET_STATUS=&quot;DOWN&quot;
 fi
 fi
 sleep 1
 done;
</code></pre>
The output will produce something like:
<pre><code>./internet_check.sh

UP 2016-05-10T23:23:06BST 4
DOWN 2016-05-10T23:23:25BST 19
UP 2016-05-10T23:23:32BST 7
</code></pre>
The number in the end of a line shows duration of previous state, i.e. 19 up, 7 seconds down.

blocks|key|1696583|text|我决定结合前面的几个答案，这样我以后就可以创建一个图表，显示起伏和它们的持续时间：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1696584|#!/bin/bash
#
#+pinger+is+a+bash+shell+script+that+monitors+the+network
#+status+every+15+seconds+and+records+if+it+is+up+'1'+or+down+'0'
#+into+the+file+log.csv+from+whence+it+may+be+plotted.
#
#+author:+J.+W.+Wooten,+Ph.D.
#+since:+11/12/2019
#+version:+1.0
#
TIMESTAMP=`date+%2B%25s`
while+[+1+]
++do
++++nc+-z+-w+5+8.8.8.8+53++>/dev/null+2>&1
online=$?
++++TIME=`date+%2B%25s`
++++if+[+$online+-eq+0+];+then
++++++echo+"`date+%2B%25Y-%25m-%25d_%25H:%25M:%25S_%25Z`+1+$(($TIME-$TIMESTAMP))"+%7C+tee+-a+log.csv
++++else
++++++echo+"`date+%2B%25Y-%25m-%25d_%25H:%25M:%25S_%25Z`+0+$(($TIME-$TIMESTAMP))"+%7C+tee+-a+log.csv
++++fi
++++TIMESTAMP=$TIME
++++sleep+15
++done;|code-block|syntax|javascript|1696585|这将每15秒输出一次CSV文件。使用Excel或Numbers，您可以读取文件并创建绘图，该绘图将显示Internet连接不可用的时间以及持续时间。如果它改变了你的睡眠间隔，那么它就是在花时间尝试连接。我希望添加功能，当它检测到网络下一步关闭时给我发送文本。|1696586|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

I decided to combine a few of the previous answers, so I could later create a plot showing ups, downs, and their durations:
<pre><code>#!/bin/bash
#
# pinger is a bash shell script that monitors the network
# status every 15 seconds and records if it is up '1' or down '0'
# into the file log.csv from whence it may be plotted.
#
# author: J. W. Wooten, Ph.D.
# since: 11/12/2019
# version: 1.0
#
TIMESTAMP=`date +%s`
while [ 1 ]
 do
 nc -z -w 5 8.8.8.8 53 &gt;/dev/null 2&gt;&amp;1
online=$?
 TIME=`date +%s`
 if [ $online -eq 0 ]; then
 echo &quot;`date +%Y-%m-%d_%H:%M:%S_%Z` 1 $(($TIME-$TIMESTAMP))&quot; | tee -a log.csv
 else
 echo &quot;`date +%Y-%m-%d_%H:%M:%S_%Z` 0 $(($TIME-$TIMESTAMP))&quot; | tee -a log.csv
 fi
 TIMESTAMP=$TIME
 sleep 15
 done;
</code></pre>
This outputs to a CSV file every 15 seconds. Using Excel or Numbers, you can read the file and create a plot which will show when the Internet connection was not available and also the duration. If it changes from your sleep interval, then it is spending time trying to connect. I hope to add the ability to send me a text when it detects network is down next.

blocks|key|1910195|text|Majal's+solution的一个变体只是测试ping返回的代码，如果站点响应，则返回0，如果没有响应，则返回1，如果网络不可达，则返回2。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1910196|++++ping+-c+1+-t+5+8.8.8.8+2&>1
++++rc=$?
++++[[+$rc+-eq+0+]]+&&+{+echo+"Connected+to+the+Internet"+;+exit+0+;+}+\
+%7C%7C+[[+$rc+-eq+1+]]+&&+{+echo+"No+reply+from+Google+DNS"+;+exit+1+;+}+\
+%7C%7C+[[+$rc+-eq+2+]]+&&+{+echo+"Network+unreachable"+;+exit+2+;+}|code-block|syntax|javascript|1910197|使用ping的优点是不需要下载任何东西，从而提高了测试速度。|1910198|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/17291233/how-can-i-check-internet-access-using-a-bash-script-on-linux/39323006#39323006^0|0|G|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|F|7|W|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|X|8|@]|9|@]|C|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

A variation on <a href="https://stackoverflow.com/questions/17291233/how-can-i-check-internet-access-using-a-bash-script-on-linux/39323006#39323006">Majal's solution</a> is just to test the return code from ping, which returns 0 if the site responds, 1 if there is no reply and 2 if the network is unreachable.
<pre><code> ping -c 1 -t 5 8.8.8.8 2&amp;&gt;1
 rc=$?
 [[ $rc -eq 0 ]] &amp;&amp; { echo &quot;Connected to the Internet&quot; ; exit 0 ; } \
 || [[ $rc -eq 1 ]] &amp;&amp; { echo &quot;No reply from Google DNS&quot; ; exit 1 ; } \
 || [[ $rc -eq 2 ]] &amp;&amp; { echo &quot;Network unreachable&quot; ; exit 2 ; }
</code></pre>
Using ping has the advantage of not needing to download anything, improving the speed of the test.

In my school, the Internet is not available (every night after 23:00 the school will kill the Internet connection, to put us to bed &gt;..&lt;), Then the ping will never stop, though I have used the parameter <code>ping -w1 ...</code>.
That is, when I use: <code>ping -q -w1 -c1 8.8.8.8</code> to check if the Internet connection is up/down, it will be there without any output and doesn't exit, just like I am using a single <code>cat</code>.
I don't know why it's like this, But I think the problem is related to the school-internet-service. Any suggestion? (I think <code>wget</code> may be a good alternative, but how can I use it?)

How can I check Internet access using a Bash script on Linux?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在我的学校，互联网是不可用的(每天晚上23点以后，学校会切断互联网连接，让我们上床睡觉>..<)，然后ping永远不会停止，尽管我使用了参数ping -w1 ...。也就是说，当我使用：ping -q -w1 -c1 8.8.8.8检查互联网连接是否打开/关闭时，它将在那里，没有任何输出，也不退出，就像我使用单个cat...

问如何在Linux上使用Bash脚本检查Internet访问？
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问如何在Linux上使用Bash脚本检查Internet访问？EN