This script is used to monitor the growth rate of...

This script is used to monitor the growth rate of disk usage for a specific file system ($FILESYSTEM) on a UNIX/Linux system. Here's a breakdown of what each line does:

1. df -h | grep $FILESYSTEM:

   • This checks the disk space usage in a human-readable format (-h) and filters the output to only show the file system specified by the $FILESYSTEM environment variable.

2. CURRENT_USAGE=$(df --block-size=1K "$FILESYSTEM" | awk 'NR==2 {print $3}'):

   • This retrieves the current disk usage (in kilobytes) for the $FILESYSTEM.
   • df --block-size=1K ensures the output is in kilobytes.
   • awk 'NR==2 {print $3}' extracts the 3rd column (used space) from the second line of the df output.

3. GROWTH=$(( ($CURRENT_USAGE - $PREVIOUS_USAGE) / 30 )):

   • This calculates the growth rate of disk usage over time in kilobytes per second based on the difference between the CURRENT_USAGE and PREVIOUS_USAGE. The previous usage value is subtracted from the current usage, and the difference is divided by 30 seconds (the time interval between checks).

4. GBS=${GROWTH:0:1}:

   • This extracts only the first digit of the GROWTH value. For example, if the growth is 456 KB/S, this will take 4.

5. echo ".$GBS GB/S":

   • This formats and prints the extracted growth rate as .X GB/S, where X is the first digit of the calculated growth.

6. PREVIOUS_USAGE=$CURRENT_USAGE:

   • Updates the PREVIOUS_USAGE variable to the current usage value so that it can be used in the next iteration to compare the growth rate over 30 seconds.

7. sleep 30:

   • Pauses the script for 30 seconds before the next iteration to monitor usage growth again.

Summary:

The code continuously monitors the growth in disk usage (in GB/S) for a specific file system ($FILESYSTEM) at 30-second intervals. It calculates and prints the first digit of the growth rate after formatting, then repeats the process. The PREVIOUS_USAGE is updated after each iteration.