Run Linux Cron Jobs Every Second Using a Bash Loop and Sleep

Linux crontab's smallest execution unit is one minute. To run a task every second, combine a minute‑based crontab entry with a custom script that loops and sleeps.

Idea

Define the actual task separately, then create a script that repeatedly executes the task with a sleep interval. Schedule the script in crontab to run each minute.

Example

1. Define the target task

Here a simple PHP script writes the current timestamp to a log file.

<?php
file_put_contents('/root/run.log', date('Y-m-d H:i:s')."
", FILE_APPEND);
?>

2. Create the execution script

Save the following Bash script as /root/test.sh. Set the desired interval (in seconds) with step, which must not exceed 60.

#!/bin/bash
# interval in seconds (cannot be greater than 60)
step=2

for (( i=0; i<60; i+=step )); do
    php /root/test.php
    sleep $step
done
exit 0

3. Add the crontab entry

Edit the crontab with crontab -e and add:

* * * * * /root/test.sh

Restart the cron service:

service crond restart

4. Verify the result

Monitor the log file:

tail -f /root/run.log

You will see timestamps printed every step seconds.