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)"
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.
While, I was working with Terraform I had a question; I will be able to destroy some specific resources using terraform destroy --target [] --target [] or terraform state -rm ; this is okay if we have 50 servers but what if I have 1000 servers and would like to terminate such as odd number instances or even number instances using the array numbers in the list or could we write a script to gather all the corrupted instances and execute that script to terminate all those instances and make that script reusable!!
Is there any way for this, I have searched all over the internet but couldn't find any solution; may be this question is dumb but I was just curious!!!!
Is there any documentation that explains this is would not be possible through terraform!!!!
You could expose the count as an output:
output "server_count" {
value = var.server_count
}
and write a script (shell/Python/etc) that takes that count as an argument and uses it to taint every odd resource:
#!/bin/bash
# usage: taint_odd_servers.sh <num servers>
SERVER_COUNT=$1
i=0
while [ $i -lt $SERVER_COUNT ]
do
REMAINDER=$(( $i % 2 ))
if [ $REMAINDER -ne 0 ]
then
terraform taint "your_server_resource[${i}]"
fi
i=$(($i+1))
done
You could then call that script like:
taint_odd_servers.sh $(terraform output server_count)
I have an infinite loop which uses aws cli to get the microservice names, it's parameters like desired tasks,number of running task etc for an environment.
There are 100's of microservices running in an environment. I have a requirement to compare the value of aws ecs metric running task for a particular microservice in the current loop and with that of the previous loop.
Say name a microservice X has the metric running task 5. As it is an infinite loop, after some time, again the loop come for the microservice X. Now, let's assume the value of running task is 4. I want to compare the running task for currnet loop, which is 4 with the value of the running task for the previous run, which is 5.
If you are asking a generic question of how to keep a previous value around so it can be compared to the current value, just store it in a variable. You can use the following as a starting point:
#!/bin/bash
previousValue=0
while read v; do
echo "Previous value=${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!
I'm currently debugging a shell script, which acts as a master-script in a data pipeline. In order to run the pipeline, you feed a bunch of arguments into the shell script. From there, the shell script sequentially calls 6 different scripts [4 in R, 2 in Python], writes out stuff to log files, and so on. Basically, my idea is to use this script to automate a data pipeline that takes a long time to run.
Right now, if any of the individual R or Python scripts break within the shell script, it just jumps to the next script that it's supposed to call. However, running script 03.py requires the data input to scripts 01.R and 02.R to be fully run and processed, otherwise 03 will produce erroneous output data which will then be written out and further processed in later scripts.
What I want to do is,
1. Break the overall shell script if there's an error in any of the R scripts
2. Output a message telling me where this error happened [line of individual R / python script]
Here's a sample of the master.sh shell script which calls the individual scripts.
#############
# STEP 2 : RUNNING SCRIPTS
#############
# A - 01.R
#################################################################
# log_file - this needs to be reassigned for every individual script
log_file=01.log
current_time=$(date)
echo "Current time: $current_time"
echo "Now running script 01. Log file output being written to $log_file_dir$log_file."
Rscript 01.R -f $input_file -s $sql_db > $log_file_dir$log_file
# current time/date
current_time=$(date)
echo "Current time: $current_time"
# B - 02.R
#################################################################
log_file=02.log
current_time=$(date)
echo "Current time: $current_time"
echo "Now running script 02. Log file output being written to $log_file_dir$log_file"
Rscript 02.R -f $input_file -s $sql_db > $log_file_dir$log_file
# PRINT OUT TIMINGS
current_time=$(date)
echo "Current time: $current_time"
This sequence is repeated throughout the master.sh script until script 06.R, after which it collates some data retrieved from output files and log files, and prints them to stout.
Here's some sample output that gets printed by my current master.sh, which shows how the script just keeps moving even though 01.R has produced an error.
file: test-data/minisample.txt
There are a total of 101 elements in file.
Using the main database.
Writing log-files to this directory: log_files/minisample/.
Writing output-csv with classifications to output/minisample.csv.
Current time: Wed Nov 14 18:19:53 UTC 2018
Now running script 01. Log file output being written to log_files/minisample/01.log.
Loading required package: stringi
Loading required package: dplyr
Attaching package: ‘dplyr’
The following objects are masked from ‘package:stats’:
filter, lag
The following objects are masked from ‘package:base’:
intersect, setdiff, setequal, union
Loading required package: RMySQL
Loading required package: DBI
Loading required package: methods
Loading required package: hms
Error: The following 2 arguments need to be provided:
-f <input file>.csv
-s <MySQL db name>
Execution halted
Current time: Wed Nov 14 18:19:54 UTC 2018
./master.sh: line 95: -1: substring expression < 0
./master.sh: line 100: -1: substring expression < 0
./master.sh: line 104: -1: substring expression < 0
Total time taken to run script 01.R:
Average time taken per user to run script 01.R:
Total time taken to run pipeline so far [01/06]:
Average time taken per user to run pipeline so far [01/06]:
Current time: Wed Nov 14 18:19:54 UTC 2018
Now running script 02. Log file output being written to log_files/minisample/02.log
Seeing as the R script 01.R produces an error, I want the script master.sh to stop. But how?
Any help would be greatly appreciated, thanks in advance!
As another user mentioned, simply running set -e will make your script terminate on first error. However, if you want more control, you can also check the exit status with ${?} or simply $? assuming your program gives an exit code of 0 on success, and non-zero otherwise.
#!/bin/bash
url=https://nosuchaddress1234.com/nosuchpage.html
error_file=errorFile.txt
wget ${url} 2> ${error_file}
exit_status=${?}
if [ ${exit_status} -ne 0 ]; then
echo -n "wget ${url} "
if [ ${exit_status} -eq 4 ]; then
echo "- Network failure."
elif [ ${exit_status} -eq 8 ]; then
echo "- Server issued an error response."
else
echo "- Other error"
fi
echo "See ${error_file} for more details"
exit ${exit_status};
fi
I like to put some boilerplate at the top of most scripts like this -
trap 'echo >&2 "ERROR in $0 at line $LINENO, Aborting"; exit $LINENO;' ERR
set -u
While coding at debugging, I usually add
set -x
And a lot of trace "comments" with colons -
: this will parse its args but only show under set -x
Then the trick is to make sure any errors you know are ok are handled.
Conditionals consume the errors, so those are safe.
if grep foo nonexistantfile
then : do the success stuff
else : if you *want* a failout here, just call false
false here will abort # args don't matter :)
fi
By the same token, if you just want to catch and ignore a known possible error -
ls $mightNotExist ||: # || says "do on fail"; : is an alias for "true"
Just always check your likely errors. Then the only thing that will crash your script is a fail.
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.