Hey there! Let's tackle this scheduled file-checking task step by step. Here's how you can make it work perfectly with your existing script and the email notification snippet you provided:

1. Upgrade Your Check_File.sh Script #

Your current script only checks once, so we need to modify it to loop every 5 minutes within the specified time window, stop as soon as the file is found, and send an email notification either way. Here's the updated version:

#!/bin/bash

# Validate input arguments
if [ $# -ne 3 ]; then
    echo "Usage: $0 <filename> <start_time> <end_time>"
    exit 1
fi

FILENAME="/home/test/$1"
START_WINDOW=$2
END_WINDOW=$3
SUBJECT="File Check Alert"
RECIPIENT="somebody@somewhere.com"
MESSAGE=""

# Loop to check file existence until window ends or file is found
while true; do
    CURRENT_TIME=$(date +"%H:%M")
    
    # Exit loop if we've passed the end of the time window
    if [[ "$CURRENT_TIME" > "$END_WINDOW" ]]; then
        MESSAGE="⚠️ File '$FILENAME' was NOT detected between $START_WINDOW and $END_WINDOW"
        break
    fi
    
    # Check if file exists
    if [ -f "$FILENAME" ]; then
        MESSAGE="✅ File '$FILENAME' was found at $CURRENT_TIME (within $START_WINDOW-$END_WINDOW)"
        break
    fi
    
    # Wait 5 minutes before next check
    sleep 300
done

# Send notification email
echo "$MESSAGE" | mail -s "$SUBJECT" "$RECIPIENT"

Don't forget to make the script executable:

chmod +x /path/to/Check_File.sh

2. Set Up Crontab Scheduled Tasks #

We'll use crontab to trigger the script at the start of each time window. Each task will kick off the script, which handles the 5-minute checks and stops automatically when the window closes or the file is found.

Edit your crontab with crontab -e, then add these lines (replace /path/to/ with the actual path to your script):

# Check file1 between 9:00-9:30 (starts at 9:00)
0 9 * * * /path/to/Check_File.sh file1 "09:00" "09:30"

# Check file3 between 10:00-10:30 (starts at 10:00)
0 10 * * * /path/to/Check_File.sh file3 "10:00" "10:30"

# Check file2 between 11:00-11:30 (starts at 11:00)
0 11 * * * /path/to/Check_File.sh file2 "11:00" "11:30"

# Check file4 between 16:00-16:30 (starts at 16:00)
0 16 * * * /path/to/Check_File.sh file4 "16:00" "16:30"

Key Notes to Keep in Mind #

• Mail Command: Ensure the mail utility is installed on your system. For Debian/Ubuntu-based systems, install it with sudo apt install mailutils. For RHEL/CentOS, use sudo yum install mailx.
• Absolute Paths: Always use full absolute paths in crontab entries and script file references to avoid issues with missing environment variables.
• Testing: To test the script without waiting for the scheduled time, run it manually with a small time window (e.g., ./Check_File.sh testfile "14:00" "14:05") and create/delete the test file to verify behavior.

内容的提问来源于stack exchange，提问作者LearningCpp