I have an infinite loop which uses aws cli to get the microservice names, it's parameters like desired tasks,number of running task etc for an environment.
There are 100's of microservices running in an environment. I have a requirement to compare the value of aws ecs metric running task for a particular microservice in the current loop and with that of the previous loop.
Say name a microservice X has the metric running task 5. As it is an infinite loop, after some time, again the loop come for the microservice X. Now, let's assume the value of running task is 4. I want to compare the running task for currnet loop, which is 4 with the value of the running task for the previous run, which is 5.
If you are asking a generic question of how to keep a previous value around so it can be compared to the current value, just store it in a variable. You can use the following as a starting point:
#!/bin/bash
previousValue=0
while read v; do
echo "Previous value=${previousValue}; Current value=${v}"
previousValue=${v}
done
exit 0
If the above script is called testval.sh. And you have an input file called test.in with the following values:
2
1
4
6
3
0
5
Then running
./testval.sh <test.in
will generate the following output:
Previous value=0; Current value=2
Previous value=2; Current value=1
Previous value=1; Current value=4
Previous value=4; Current value=6
Previous value=6; Current value=3
Previous value=3; Current value=0
Previous value=0; Current value=5
If the skeleton script works for you, feel free to modify it for however you need to do comparisons.
Hope this helps.
I dont know how your input looks exactly, but something like this might be useful for you :
The script
#!/bin/bash
declare -A app_stats
while read app tasks
do
if [[ ${app_stats[$app]} -ne $tasks && ! -z ${app_stats[$app]} ]]
then
echo "Number of tasks for $app has changed from ${app_stats[$app]} to $tasks"
app_stats[$app]=$tasks
else
app_stats[$app]=$tasks
fi
done <<< "$( cat input.txt)"
The input
App1 2
App2 5
App3 6
App1 6
The output
Number of tasks for App1 has changed from 2 to 6
Regards!
Related
I am trying to create my first bash script. The goal of this script is to check at what rate my public IP changes. It is a fairly straight forward script. First it checks if the new address is different from the old one. If so then it should update the old one to the new one and print out the date along with the new IP address.
At this point I have created a simple script in order to accomplish this. But I have two main problems.
First the script keeps on printing out the IP even tough it hasn't changed and I have updated the PREV_IP with the CUR_IP.
My second problem is that I want the output to direct to a file instead of outputting it into the terminal.
The interval is currently set to 1 second for test purposes. This will change to a higher interval in the final product.
#!/bin/bash
while true
PREV_IP=00
do
CUR_IP=$(curl https://ipinfo.io/ip)
if [ $PREV_IP != "$CUR_IP" ]; then
PREV_IP=$CUR_IP
"$(date)"
echo "$CUR_IP"
sleep 1
fi
done
I also get a really weird output. I have edited my public IP to xx.xxx.xxx.xxx:
Sat 20 Mar 09:45:29 CET 2021
xx.xxx.xxx.xxx
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- --:--:-- --:--:--
while true
PREV_IP=00
do
is the reason you are seeing ip each loop. It's the same as while true; PREV_IP=00; do. The exit status of true; PREV_IP=00 is the exit status of last command - the exit status of assignment is 0 (success) - so the loop will always execute. But PREV_IP will be reset to 00 each loop... This is a typo and you meant to set prev_ip once, before the loop starts.
"$(date)"
will try execute the output of date command, as a next command. So it will print:
$ "$(date)"
bash: sob, 20 mar 2021, 10:57:02 CET: command not found
And finally, to silence curl, read man curl first and then find out about -s. I use -sS so errors are also visible.
Do not use uppercase variables in your scripts. Prefer lower case variables. Check you scripts with http://shellcheck.net . Quote variable expansions.
I would sleep each loop. Your script could look like this:
#!/bin/bash
prev=""
while true; do
cur=$(curl -sS https://ipinfo.io/ip)
if [ "$prev" != "$cur" ]; then
prev="$cur"
echo "$(date) $cur"
fi
sleep 1
done
that I want the output to direct to a file instead of outputting it into the terminal.
Then research how redirection works in shell and how to use it. The simplest would be to redirect echo output.
echo "$(date) $cur" >> "a_file.txt"
The interval is currently set to 1 second for test purposes. This will change to a higher interval in the final product.
You are still limited with the time it takes to connect to https://ipinfo.io/ip. And from ipinfo.io documentation:
Free usage of our API is limited to 50,000 API requests per month.
And finally, I wrote a script where I tried to use many public services as I found ,get_ip_external for getting external ip address. You may take multiple public services for getting ipv4 address and choose a random/round-robin one so that rate-limiting don't kick that fast.
I want to create a random seed in a bash script but somehow know how to calculate the same random seed again later on.
Suppose I have a range of servers id : 1 to 10. I want to randomly select a server to run a test on. I can do that by using the RANDOM function and see the value
echo $((1 + RANDOM % 10))
6
Then run the test on server id 6.
I do this in a loop for 5 times.
Is there a way to re-calculate the values (ids of servers) later on to see where the tests were ran on ? I should mention I do not wish to store the ids in an array.
Or if there is a way other than using the RANDOM function to accomplish this ?
Assuming you want re-playable "random" sequence, you could use the command shuf:
$ printf '%s\n' server{1..10} | shuf --random-source file
server3
server6
server5
server9
server1
server2
server4
server8
server7
server10
As long as you use the same file as random source, the sequence will stay the same and could be replayed in the same order.
For info, you can also use the command shuf -e server{1..10} --random-source file if you want to get rid of the printf ... | command.
Use -i option of this shuf command and if you have a consecutive range of number to shuffle.
Let's say we had a loop that we want to have run as quickly as possible. Let's say something was being done to a list of hosts inside that loop; just for the sake of argument, let's say it was a redis query. Let's say that the list of hosts may change occasionally due to hosts being added/removed from a pool (not load balanced); however, the list is predictable (e.g., they all start with “foo” and end with 2 digits. So we want to run this occasionally; say, once every 15 minutes:
listOfHosts=$(dig +noall +ans foo{00..99}.domain | while read -r n rest; do printf '%s\n' ${n%.}; done)
to get the list of hosts. Let's say our loop looked something like this:
while :; do
for i in $listOfHosts; do
redis-cli -h $i llen something
done
(( ( $(date +%s) % 60 * 15) == 0 )) && callFunctionThatSetslistOfHosts
done
(now obviously there's some things missing, like testing to see if we've already run callFunctionThatSetslistOfHosts in the current minute and only running it once, and doing something with the redis output, and maybe the list of hosts should be an array, but basically this is it.)
How can we run callFunctionThatSetslistOfHosts asynchronously so that it doesn't slow down the loop. I.e., have it running in the background setting listOfHosts occasionally (e.g. once every 15 minutes), so that the next time the inner loop is run it gets a potentially different set of hosts to run the redis query on?
My major problem seems to be that in order to set listOfHosts in a loop, that loop has to be a subshell, and listOfHosts is local to that subshell, and setting it doesn't affect the global listOfHosts.
I may resort to pipes, but will have to poll the reader before generating a new list — not that that's terribly bad if I poll slowly, but I thought I'd present this as a problem.
Thanks.
I have a simple script that I need to run every 15 minutes everyday (until I get to the last record in my database) giving it greater argument. I know how to do this with the constant argument - example:
*/15 * * * * ./my_awesome_script 1
But I need this, let's say, we start from 8:00 AM:
at 8:00 it should run ./my_awesome_script 1
at 8:15 it should run ./my_awesome_script 2
at 8:30 it should run ./my_awesome_script 3
at 8:45 it should run ./my_awesome_script 4
at 9:00 it should run ./my_awesome_script 5
...
How to make something like this?
I came up with temporary solution:
#!/bin/bash
start=$1
stop=$2
for i in `seq $start $stop`
do
./my_awesome_script $i
sleep 900
done
Writing a wrapper script is pretty much necessary (for sanity's sake). The script can record in a file the previous value of the number and increment it and record the new value ready for next time. Then you don't need the loop. How are you going to tell when you've reached the end of the data in the database? You need to know about how you want to handle that, too.
New cron entry:
*/15 * * * * ./wrap_my_awesome_script
And wrap_my_awesome_script might be:
crondir="$HOME/cron"
counter="$crondir/my_awesome_script.counter"
[ -d "$crondir" ] || mkdir -p "$crondir"
[ -s "$counter" ] || echo 0 > "$counter"
count=$(<"$counter")
((count++))
echo "$count" > $counter
"$HOME/bin/my_awesome_script" "$count"
I'm not sure why you use ./my_awesome_script; it likely means your script is in your $HOME directory. I'd keep it in $HOME/bin and use that name in the wrapper script — as shown.
Note the general insistence on putting material in some sub-directory of $HOME rather than directly in $HOME. Keeping your home directory uncluttered is generally a good idea. You can place the files and programs where you like, of course, but I recommend being as organized as possible. If you aren't organized then, in a few years time, you'll wish you had been.
Hello I want to ask a question that is repeated here.
I have four servers in bash script defined like in the code below.
For each server, I want to maintain the ID of the process I have started on it.
Just for testing, I wanted to initialize each array with 10 20 30 40.
And see if I can access these elements as expected. However I cannot access the elements.
Could someone tell me what exactly I am doing wrong.
#!/bin/bash
SERVER_LIST=("server1" "server2" "server3")
for server in ${SERVER_LIST[#]} ; do
echo $server
arrayName=$server"process"
echo $arrayName
set -a "$arrayName=(10 20 30 40)"
done
current_sever=${SERVER_LIST[0]}
arrayName=$current_server"process"
# The attempt below is failing.
eval "echo Server ${current_server} \${$arrayName[*]}"
echo $(eval echo \${arrayName[*]})Server server1
server1process
It gives me output as follows -
Server server1
server1process
Can someone help please.
Also can you please tell me how to append new element to the array?
I tried the following, but it doesn't work -
sleep 10 &
arrayName=$current_server"process"
eval "\${$arrayName[*]}+=$!"
Try replacing line 8:
set -a "$arrayName=(10 20 30 40)"
with:
eval "$arrayName=(10 20 30 40)"