This question already has answers here:
Checking host availability by using ping in bash scripts
(11 answers)
Closed 5 years ago.
I want to check the ping replies on two IP addresses and if they are both up, then I execute a command.
For example:
ping 8.8.8.8 on response do
ping 8.8.4.4 on response
execute command
Is there a simple bash script to do this?
According to the manpage on ping:
If ping does not receive any reply packets at all it will exit with code 1. If a packet count and deadline are both specified, and fewer than count packets are received by the time the deadline has arrived, it will also exit with code 1. On other error it exits with code 2. Otherwise it exits with code 0. This makes it possible to use the exit code to see if a host is alive or not.
Thus you can rely on the exit code to determine whether to continue in your script.
ping 8.8.8.8 -c 1
if [ $? = 0 ]
then
echo ok
else
echo ng
fi
Try ping only 1 time with -c 1 option. Change to any number as you like.
$? is the exit code of the previous command. You can refer ping's exit code with it.
Modify the above code snippet to what you want.
Bash commands to return yes or no if a host is up.
Try hitting a site that doesn't exist:
eric#dev ~ $ ping -c 1 does_not_exist.com > /dev/null 2>&1; echo $?
2
Try hitting a site that does exist:
eric#dev /var/www/sandbox/eric $ ping -c 1 google.com > /dev/null 2>&1; echo $?
0
If it returns 0, then the host is evaluated to be responsive. If anything other than zero, then it was determined that the host is unreachable or down.
Related
I created a bash script to ping my local network to see which hosts is up and I have a problem in stopping the Ping process by using ctrl+C once it is started
the only way i found to suspend it but even the kill command doesn't work with the PID of the Ping
submask=100
for i in ${submask -le 110}
do
ping -n 2 192.168.1.$submask
((submask++))
done
Ctrl + C exit ping, but another ping starts. So you can use trap.
#!/bin/bash
exit_()
{
exit
}
submask=100
while [ $submask -le 110 ]
do
fping -c 2 192.168.77.$submask
((submask++))
trap exit_ int
done
I suggest you to limit the amount of packets sent with ping with the option -c.
I also corrected the bash syntax, guessing what you intend to do.
Finally, it is faster to run all the ping processes in parallel with the operand &.
Try:
for submask in ${100..110}
do
echo ping -c 1 192.168.1.$submask &
done
This question already has answers here:
Exit when one process in pipe fails
(2 answers)
Closed 4 years ago.
Even if the mycode.sh has non-0 exit code this command returns 0 as ssh connection was successful. How to get the actual return code of the .sh on remote server?
/home/mycode.sh '20'${ODATE} 1 | ssh -L 5432:localhost:5432 myuser#myremotehost cat
This is not related to SSH, but to how bash handles the exit status in pipelines. From the bash manual page:
The return status of a pipeline is the exit status of the last command, unless the pipefail option is enabled. If pipefail is enabled, the pipeline's return status is the value of the last (rightmost) command to exit with a non-zero status, or zero if all commands exit successfully. If the reserved word ! precedes a pipeline, the exit status of that pipeline is the logical negation of the exit status as described above. The shell waits for all commands in the pipeline to terminate before returning a value.
If you want to check that there was an error in the pipeline due to any of the commands involved, just set the pipefail option:
set -o pipefail
your_pipeline_here
echo $? # Prints non-zero if something went wrong
It is not possible to actually send the exit status to the next command in the pipeline (in your case, ssh) without additional steps. If you really want to do that, the command will have to be split like this:
res="$(/home/mycode.sh '20'${ODATE} 1)"
if (( $? == 0 )); then
echo -n "$res" | ssh -L 5432:localhost:5432 myuser#myremotehost cat
else
# You can do anything with the exit status here - even pass it on as an argument to the remote command
echo "mycode.sh failed" >&2
fi
You may want to save the output of mycode.sh to a temporary file instead of the $res variable if it's too large.
/home/mycode.sh is located onto the local host.
the ssh command is running cat on the remote server.
All text printed to the standard output of the /home/mycode.sh is redirected to the cat standard input.
The man ssh reads:
EXIT STATUS
ssh exits with the exit status of the remote command or with 255 if an error occurred.
Conclusion: the ssh exists with the EXIT STATUS of the cat or 255 if an error occurred.
if /home/mycode.sh script prints commands to the standard input, they can be run on the remote server when the cat is not present:
/home/mycode.sh '20'${ODATE} 1 | ssh -L 5432:localhost:5432 myuser#myremotehost
In my test, the EXIT STATUS of the last command executed on the remote server is returned by ssh:
printf "%s\n" "uname -r" date "ls this_file_does_not_exist" |\
ssh -L 5432:localhost:5432 myuser#myremotehost ;\
printf "EXIT STATUS of the last command, executed remotely with ssh is %d\n" $?
4.4.0-119-generic
Wed Aug 29 02:55:04 EDT 2018
ls: cannot access 'this_file_does_not_exist': No such file or directory
EXIT STATUS of the last command, executed remotely with ssh is 2
I need to check my connection to a spesific port every 5 minutes, currently i can't use ping command, so i need other alternative to do this.I want to execute this command in shell script
Can someone help me to show some example for this case?
port=80
ip=8.8.8.8
checkIntervalSecs=5
timeoutSecs=1
while true ; do
if $(nc -z -v -w$timeoutSecs $ip $port &>/dev/null); then
echo "Server is up!"
else
echo "Server is down!"
fi
sleep $checkIntervalSecs
done
This runs until you kill it. For an explanation of the nc command, it is basically taken from SO question #IporSircer suggested.
I am running a script from remote machine via ssh:
ssh 'some_cmd;my_script'
Now, I want to store exit status of shell script on my local machine.
How can I do it?
Assuming nothing goes wrong with ssh itself, its exit status is the exit status of the last command executed on the remote host. (If something does go wrong, its exit status is 255.)
$ ssh remotehost exit 13
$ echo $?
13
I had same problem. I don't think the previous answers will work (at least, they did not work for me).
This is what worked for me: I ran my command and displayed the exit code and captured it in a variable.
Ensure you protect the $? sign with the escape sequence, \:
# retcode=$(ssh test#1.2.3.4 "grep -q test /etc/passwd ; echo \$? " 2>/dev/null)
# echo $retcode
# 1
I want to use ping to check to see if a server is up. How would I do the following:
ping $URL
if [$? -eq 0]; then
echo "server live"
else
echo "server down"
fi
How would I accomplish the above? Also, how would I make it such that it returns 0 upon the first ping response, or returns an error if the first ten pings fail? Or, would there be a better way to accomplish what I am trying to do above?
I'ld recommend not to use only ping. It can check if a server is online in general but you can not check a specific service on that server.
Better use these alternatives:
curl
man curl
You can use curl and check the http_response for a webservice like this
check=$(curl -s -w "%{http_code}\n" -L "${HOST}${PORT}/" -o /dev/null)
if [[ $check == 200 || $check == 403 ]]
then
# Service is online
echo "Service is online"
exit 0
else
# Service is offline or not working correctly
echo "Service is offline or not working correctly"
exit 1
fi
where
HOST = [ip or dns-name of your host]
(optional )PORT = [optional a port; don't forget to start with :]
200 is the normal success http_response
403 is a redirect e.g. maybe to a login page so also accetable and most probably means the service runs correctly
-s Silent or quiet mode.
-L Defines the Location
-w In which format you want to display the response
-> %{http_code}\n we only want the http_code
-o the output file
-> /dev/null redirect any output to /dev/null so it isn't written to stdout or the check variable. Usually you would get the complete html source code before the http_response so you have to silence this, too.
nc
man nc
While curl to me seems the best option for Webservices since it is really checking if the service's webpage works correctly,
nc can be used to rapidly check only if a specific port on the target is reachable (and assume this also applies to the service).
Advantage here is the settable timeout of e.g. 1 second while curl might take a bit longer to fail, and of course you can check also services which are not a webpage like port 22 for SSH.
nc -4 -d -z -w 1 ${HOST} ${PORT} &> /dev/null
if [[ $? == 0 ]]
then
# Port is reached
echo "Service is online!"
exit 0
else
# Port is unreachable
echo "Service is offline!"
exit 1
fi
where
HOST = [ip or dns-name of your host]
PORT = [NOT optional the port]
-4 force IPv4 (or -6 for IPv6)
-d Do not attempt to read from stdin
-z Only listen, don't send data
-w timeout
If a connection and stdin are idle for more than timeout seconds, then the connection is silently closed. (In this case nc will exit 1 -> failure.)
(optional) -n If you only use an IP: Do not do any DNS or service lookups on any specified addresses, hostnames or ports.
&> /dev/null Don't print out any output of the command
You can use something like this -
serverResponse=`wget --server-response --max-redirect=0 ${URL} 2>&1`
if [[ $serverResponse == *"Connection refused"* ]]
then
echo "Unable to reach given URL"
exit 1
fi
Use the -c option with ping, it'll ping the URL only given number of times or until timeout
if ping -c 10 $URL; then
echo "server live"
else
echo "server down"
fi
Short form:
ping -c5 $SERVER || echo 'Server down'
Do you need it for some other script? Or are trying to hack some simple monitoring tool? In this case, you may want to take a look at Pingdom: https://www.pingdom.com/.
I using the following script function to check servers are online or not. It's useful when you want to check multiple servers. The function hide the ping output, and you can handle separately the server live or server down case.
#!/bin/bash
#retry count of ping request
RETRYCOUNT=1;
#pingServer: implement ping server functionality.
#Param1: server hostname to ping
function pingServer {
#echo Checking server: $1
ping -c $RETRYCOUNT $1 > /dev/null 2>&1
if [ $? -ne 0 ]
then
echo $1 down
else
echo $1 live
fi
}
#usage example, pinging some host
pingServer google.com
pingServer server1
One good solution is to use MRTG (a simple graphing tool for *NIX) with ping-probe script. look it up on Google.
read this for start.
Sample Graph: