Run check at minute 0, 15, 30, and 45 of every hour.
Which schedule is appropriate?
*/15 in the minute field selects every 15-minute step.
Detailed explanation
15 * * * * checkIncorrect. It runs only at minute 15.
Incorrect. It runs only at minute 15.
* 15 * * * checkIncorrect. It runs every minute during hour 15.
Incorrect. It runs every minute during hour 15.
*/15 * * * * checkCorrect. */15 matches minutes 0, 15, 30, and 45.
Correct. */15 matches minutes 0, 15, 30, and 45.
* */15 * * * checkIncorrect. It steps through hours and runs every minute in those hours.
Incorrect. It steps through hours and runs every minute in those hours.
Try it yourself
An example you can run in a temporary verification environment.
seq 0 59 | awk '$1 % 15 == 0' | paste -sd, -Expected result
0,15,30,45Key points
- */N is a step
- Use minute field
- Four times per hour
Notes
- Environment: GNU seq / awkによる時刻集合確認
- Command output formatting can vary slightly by distribution or tool version.
- Run the example in a temporary directory or process when possible.
Foundation review
Read the scope first
Check whether the command acts on the current shell, a new process, an existing process, or a file.
Verify the observable result
Use the supplied command and compare the output with the expected result.