Bash脚本开发：如何监控CPU使用率以利用空闲时间

Hey there! Since you're new to shell scripting, let's build this CPU monitoring script together—super practical and easy to follow. I get that most online examples only print CPU usage percentages, so we'll focus on the trigger logic you need: firing up a CPU-heavy process when the system is idle.

First, let's break this down into simple, manageable parts:

1. Get Accurate CPU Idle Percentage #

We'll use mpstat (part of the sysstat package) because it's far more reliable for scripting than interactive tools like top. If you don't have it installed yet:

• Debian/Ubuntu: sudo apt install sysstat
• RHEL/CentOS: sudo yum install sysstat

This command grabs the average CPU idle percentage over 1 second, rounded to an integer for easy comparison:

IDLE_PERCENT=$(mpstat 1 1 | awk '/Average/ {print int($12)}')

2. A Simple CPU-Intensive Process #

For testing, a basic infinite empty loop works perfectly—it will hog one full CPU core. If you need to load multiple cores, we'll cover that later. Here's the loop:

while true; do :; done

The : is a no-op (no operation) command, so the loop runs nonstop without doing anything else.

3. Full Working Script #

This script will monitor CPU idle time, start the CPU-hog process when idle, and kill it once the system is busy again. Tweak the threshold to match your needs!

#!/bin/bash

# Set your CPU idle threshold (percent) - adjust this as needed
IDLE_THRESHOLD=80

# Infinite loop to keep monitoring
while true; do
    # Get current CPU idle percentage (integer)
    CURRENT_IDLE=$(mpstat 1 1 | awk '/Average/ {print int($12)}')
    echo "Current CPU idle: ${CURRENT_IDLE}%"

    # Check if CPU is idle enough to trigger our process
    if [ "$CURRENT_IDLE" -gt "$IDLE_THRESHOLD" ]; then
        echo "CPU is idle - starting CPU load process..."
        # Start the CPU-hog loop in the background
        while true; do :; done &
        # Save the process ID to kill it later
        LOAD_PID=$!
        echo "Load process started with PID: $LOAD_PID"

        # Wait until CPU is no longer idle, then kill the load process
        while true; do
            CHECK_IDLE=$(mpstat 1 1 | awk '/Average/ {print int($12)}')
            if [ "$CHECK_IDLE" -le "$IDLE_THRESHOLD" ]; then
                echo "CPU is busy again - stopping load process..."
                kill $LOAD_PID
                break
            fi
            sleep 5  # Check every 5 seconds while waiting
        done
    fi

    # Wait 10 seconds before checking again (adjust this interval if needed)
    sleep 10
done

4. Customization Tips #

• Load multiple CPU cores: If you want to use more than one core, replace the single background loop with a loop that starts multiple processes:

  # Start 4 load processes (adjust the number as needed)
  PIDS=()
  for i in {1..4}; do
      while true; do :; done &
      PIDS+=($!)
  done
  # Then kill all of them later:
  kill "${PIDS[@]}"
  

• Adjust thresholds/check intervals: Tweak IDLE_THRESHOLD, sleep 10, or sleep 5 to match your system's behavior.
• Verify column number first: Run mpstat 1 1 manually to confirm the idle percentage column (some systems might use column 13 instead of 12—just adjust the awk command if needed).

Save this script as cpu_monitor.sh, make it executable with chmod +x cpu_monitor.sh, and run it with ./cpu_monitor.sh. You can also set it to run at startup if you need it to run continuously!

内容的提问来源于stack exchange，提问作者gizmo