I want to ssh IP obtained in varible "a". this works fine if everything is ok.
But if my command "commandToGetIP" get stuck in network or by any chance it will not return any output my script will go in hung state.
Now what i need to get is this command "commandToGetIP" should wait only for 10 sec and come out giving some message
a=commandToGetIP <DeviceID>
ssh $a
I want to ssh IP obtained in varible "a". this works fine if everything is ok.
But if my command "commandToGetIP" get stuck in network or by any chance it will not return any output my script will go in hung state.
Now what i need to get is this command "commandToGetIP" should wait only for 10 sec and come out giving some message
So, bash has a built in command to timeout another command. If the command takes too long, timeout will kill it with exit code 143. Using this information, I am checking to see if the exit code was not 143 before performing the ssh command. Otherwise, it'll do whatever you want it to do when commandToGetIP takes too long.
timeout 10 commandToGetIP <DeviceID> | read ip
result=$?
if [ "$result" != "143" ]; then
ssh $ip
else
# What we do if it times out
fi
Related
Due to some issues I wont elaborate here to not waste time, I made a bash script which will ping google every 10 minutes and if there is a response it will keep the loop running and if not then the PC will restart. After a lot of hurdle I have been able to make the script and also make it start on bootup. However the issue is that i want to see the results on the terminal, meaning I want to keep monitoring it but the terminal does not open on bootup. But it does open if I run it as ./net.sh.
The script is running on startup, that much I know because I use another script to open an application and it works flawlessly.
My system information
NAME="Linux Mint"
VERSION="18.3 (Sylvia)"
ID=linuxmint
ID_LIKE=ubuntu
PRETTY_NAME="Linux Mint 18.3"
VERSION_ID="18.3"
HOME_URL="http://www.linuxmint.com/"
SUPPORT_URL="http://forums.linuxmint.com/"
BUG_REPORT_URL="http://bugs.launchpad.net/linuxmint/"
VERSION_CODENAME=sylvia
UBUNTU_CODENAME=xenial
The contents of my net.sh bash script are
#! /bin/bash
xfce4-terminal &
sleep 30
while true
do
ping -c1 google.com
if [ $? == 0 ]; then
echo "Ping Sucessful. The Device will Continue Operating"
sleep 600
else
systemctl reboot
fi
done
I have put the scripts in /usr/bin and inserted the scripts for startup at boot in /etc/rc.local
So I did some further research and with help from reddit I realized that the reason I couldnt get it to show on terminal was because the script was starting on bootup but I needed it to start after user login. So I added the script on startup application (which can be found searching on start menu if thats whats it called). But it was still giving issues so I divided the script in two parts.
I put the net.sh script on startup and directed that script to open my main script which i named net_loop.sh
This is how the net.sh script looks
#! /bin/bash
sleep 20
xfce4-terminal -e usr/bin/net_loop.sh
And the net_loop.sh
#! /bin/bash
while true
do
ping -c1 google.com
if [ $? == 0 ]; then
echo "Ping Sucessful. The Device will Continue Operating"
sleep 600
else
systemctl reboot
fi
done
The results are the results of the net_loop.sh script are open in another terminal.
Note: I used help from this thread
If minute interval is usable why not use "cron" to start your?
$> crontab –e
or
$> sudo crontab –e
I'm running an Ubuntu server to mine crypto. It's not a very stable coin yet and their main node gets disconnected sometimes. When this happens it crashes the program through fatal error.
At first I wrote a loop script so it would keep running after a crash and just try again after 15 seconds:
while true;
do ./miner <somecodetoconfiguretheminer> &&break;
sleep 15
done;
This works, but is inefficient. Sometimes the loop will keep running for 30 minutes until the main node is back up - which costs me 30 minutes of hashing power unused. So I want it to run a second miner for 15 minutes to mine another coin, then check the first miner again if its working yet.
So basically: Start -> Mine coin 1 -> if crash -> Mine coin 2 for 15 minutes -> go to Start
I tried the script below but the server just becomes unresponsive once the first miner disconnects:
while true;
do ./miner1 <somecodetoconfiguretheminer> &&break;
timeout 900 ./miner2
sleep 15
done;
Ive read through several topics / questions on how &&break works, timeout works and how while true works but I can't figure out what I'm missing here.
Thanks in advance for the help!
A much simpler solution would be to run both of the programs all the time, and lower the priority of the less-preferred one. On Linux and similar systems, that is:
nice -10 ./miner2loop.sh &
./miner1loop.sh
Then the scripts can be similar to your first one.
Okay, so after trial and error - and some help - I found out that there is nothing wrong with my initial code. Timeout appears to behave differently on my linux instance when used in terminal than in a bash script. If used in Terminal it behaves as it should, it counts down and then kills the process it started. If used in bash however - it acts as if I typed 'sleep' and then after counting down stops.
Apparently this has to do with my Ubuntu instance (running on a VPS). Even though I installed latest versions of coreutils, have all the latest versions installed through apt-get update etc. This is the case for me on Digital Ocean as well as Google Compute.
The solution is to use the Timeout code as a function within the bash script, as found on another thread in stackoverflow. I named the function timeout2 as to not confuse the system in triggering the not properly working timeout command:
#!/bin/bash
# Executes command with a timeout
# Params:
# $1 timeout in seconds
# $2 command
# Returns 1 if timed out 0 otherwise
timeout2() {
time=$1
# start the command in a subshell to avoid problem with pipes
# (spawn accepts one command)
command="/bin/sh -c "$2""
expect -c "set echo "-noecho"; set timeout $time; spawn -noecho
$command; expect timeout { exit 1 } eof { exit 0 }"
if [ $? = 1 ] ; then
echo "Timeout after ${time} seconds"
fi
}
while true;
do
./miner1 <parameters for miner> && break;
sleep 5
timeout2 300 ./miner2 <parameters for miner>
done;
I am using guestcontrol with Virtual Box with a Windows host and a Linux (RHEL7) guest. I want to do some config from the host to the guest by running a shell script on the guest (from a .bat on the host). This is fine and the script runs, however, it hangs when I call the reboot (I believe it is because nothing is returned). So when the following .sh is called:
#!/bin/bash
echo "here"
exit
The .bat file shows "here" and then exits (or if I use pause gives the correct message). However, when I add the reboot, the .bat never processes anything past where it calls the script. I think this would be because the guest never tells the host that the script is complete.
I have tried things like:
#!/bin/bash
{ sleep 1; reboot; } >/dev/null &
exit
or even:
#!/bin/bash
do_reboot(){
sleep 1
reboot
}
do_reboot() &
exit
but the .bat never gets past the line where it runs the .sh
How can I tell the host that the .sh script (on the guest) is complete so it can continue with the .bat script?
We need to make sure there are no sub processes running, so we want to do a no heads up using the nohup command. So the script simply becomes this:
#!/bin/bash
nohup reboot &> /tmp/nohup.out </dev/null &
exit
The stdin and stdout were causing the issues, so this just sends them into the void so that the script will not be waiting for any input from any other processes.
If you have any issues with this script, you could do something like:
#!/bin/bash
nohup /path/to/reboot_delay.sh &> /tmp/nohup.out </dev/null &
exit
And then in /path/to/reboot_delay.sh you would have:
#!/bin/bash
sleep 10 # or however many seconds you need to wait for something to happen
reboot
This way you could even allow some time for something to finish etc, yet the host machine (or ssh or wherever you are calling this from) would still know the script had finished and do what it needs to do.
I hope this can help people in future.
My script is:
for i in $(seq $nb_lignes) a list of machines
do
ssh root#$machine -x "java ....."
sleep 10
done
--> i execute this script from machine C
i have two machines A and B ($nb_lignes=2)
ssh root#$machineA -x "java ....." : create a node with Pastry overlay
wait 10 secondes
ssh root#$machineB -x "java .....":create another node join the first (that's way i have use sleep 10 secondes)
i run the script from machine C:
i'd like that it display : node 1 is created , wait 10 seconds and display node 2 is created
My problem: it display node 1 is created only
i tape ctrl+c it diplay node 2 is created
PS: the two process java are still runing in machine A and B
Thank you
From the way I'm reading this, armani is correct; since your java program does not exit, the second iteration of the loop doesn't get run until you "break" the first one. I would guess that the Java program is ignoring a break signal sent to it by ssh.
Rather than backgrounding each SSH with a &, you're probably better off using the tools provided to you by ssh itself. From the ssh man page:
-f Requests ssh to go to background just before command execution.
This is useful if ssh is going to ask for passwords or
passphrases, but the user wants it in the background. This
implies -n. The recommended way to start X11 programs at a
remote site is with something like ssh -f host xterm.
So ... your script would look something like this:
for host in machineA machineB; do
ssh -x -f root#${host} "java ....."
sleep 10
done
Try the "&" character after the "ssh" command. That spawns the process separately [background] and continues on with the script.
Otherwise, your script is stuck running ssh.
EDIT: For clarity, this would be your script:
for i in $(seq $nb_lignes) a list of machines
do
ssh root#$machine -x "java ....." &
sleep 10
done
I have several binary in the same folder that I want to run in a sequence.
Each binary does not terminate by itself and is waiting for data from a socket interface. Also, I need to decide whether to run the next binary based on the output of the previous binary. I am thinking of running them in the background and redirect the output of the previous binary to a file and "grep" for the keyword. However, unless I use wait, I couldn't capture all the output I want from running the previous binary. But if I use wait, I can't get control back because the binary is listening on socket and wouldn't return.
What can I do here?
a sample code here:
/home/test_1 & > test_1_log
test_1_id=$!
wait
===> I also want to grep "Success" in test_1_log here.
===> can't get here because of wait.
/home/test_2 & >test_2_log
test_2_id=$!
wait
Thanks
Can you use sleep instead of wait?
The problem is that you can't wait for it to return, because it won't. At the same time, you have to wait for some output. If you know that "Success" or something will be output, then you can loop until that line appears with a sleep.
RC=1
while [ $RC != 0 ]
do
sleep 1
grep -q 'Success' test_1_log
RC=$?
done
that also allows you to stop waiting after, say, 10 iterations or something, making sure your script exits