Automated File Retrieval (Cronjob)

Configure a cronjob to download a sample text file every 30 minutes, ensuring the local copy is overwritten without creating duplicates:

edit crontab:

crontab -e

append cron task:

*/30 * * * * wget -q -O /tmp/sample3.txt https://filesamples.com/samples/document/txt/sample3.txt

tip

Using the -O flag with wget ensures the file is saved to a specific filename, effectively replacing the previous version and preventing duplicate files like sample3.txt.1.

How to Save & Exit (Nano)

After appending the cron task, follow these steps to save your changes and exit the editor:

1. Press Ctrl + X (Exit).
2. Press Y (Yes) to confirm saving the modified buffer.
3. Press Enter to finalize the filename and return to the terminal.

Cron Syntax Reference

A cron expression consists of five fields representing the time and frequency of a task:

* * * * *
│ │ │ │ │
│ │ │ │ └── Day of week (0 - 6) (Sunday to Saturday)
│ │ │ └──── Month (1 - 12)
│ │ └────── Day of month (1 - 31)
│ └──────── Hour (0 - 23)
└────────── Minute (0 - 59)

Field Values & Operators

Operator	Description	Example
*	Any value: Matches all possible values for that field.	* * * * * (Every minute)
,	Value list separator: Specific points in time.	15,45 * * * * (At minute 15 and 45)
-	Range of values: Continuous range.	0 9-17 * * * (Every hour from 9 AM to 5 PM)
/	Step values: Incremental jumps.	*/15 * * * * (Every 15 minutes)

Common Examples

• 0 0 * * *: Run daily at midnight.
• 0 12 * * 1: Run every Monday at 12:00 PM.
• */30 * * * *: Run every 30 minutes (as used in the example above).

info

For complex schedules, you can use Crontab.guru, a helpful visual editor and generator for cron schedules.