How can I run a particular script every second?

Question

I have tried using crontab, but it is limited to minutes. Is there any other option?

I have also tried something like:

watch -n 1 sh /path-to-script/try.sh

But whenever I close the terminal it stops. I want something which continuously works in the background.

Answer 1

Use a script with the while loop and nohup.

the_script.sh:

while :; do
  /path-to-script/try.sh
  sleep 1
done

Run the_script.sh immune to hangups:

nohup /path/to/the_script.sh > /dev/null

Replace /dev/null with some file path if you care what's in the stdout.

Answer 2

Based on the information you have given, the best answer is likely the simplest one. Use a shell script with a infinite loop and a 1 second delay.

#!/bin/bash
# Program that checks if MySQL is running
while [ 1 = 1 ]; do
<your code here>
sleep 1
done

Have the script run outside a terminal. That way it runs in the background.

For a more specific answer, I'd need to know what command you use and what you do if it's not running. Eg. send a notification or email.

Answer 3

This routine will continuously run try.sh every second unless it is already running. If already running, it will pause until the former execution ends.

loop_script.sh: 




while true; do  
   if [[ ! $(pgrep -x /path-to-script/try.sh) -gt 1 ]]; then  
      /path-to-script/try.sh  
   fi  
  
   sleep 1  
done  

Execute this way:

nohup /path/to/loop_script.sh & > /dev/null

Then hit ^C to regain console.

Must use kill command to stop loop_script.sh