In a user crontab, run /home/app/bin/check.sh at minutes 0, 15, 30, and 45 of every hour.
Which entry is appropriate?
The first crontab field is minutes. */15 means every 15-minute step starting at minute zero.
Detailed explanation
*/15 * * * * /home/app/bin/check.shCorrect. */15 selects 0, 15, 30, and 45 minutes.
Correct. */15 selects 0, 15, 30, and 45 minutes.
15 * * * * /home/app/bin/check.shIncorrect. It runs only at minute 15 of each hour.
Incorrect. It runs only at minute 15 of each hour.
* 15 * * * /home/app/bin/check.shIncorrect. It runs every minute during hour 15.
Incorrect. It runs every minute during hour 15.
0 */15 * * * /home/app/bin/check.shIncorrect. */15 in the hour field means every 15 hours.
Incorrect. */15 in the hour field means every 15 hours.
Try it yourself
An example you can run in a temporary verification environment.
printf '%s
' '*/15 * * * * /home/app/bin/check.sh' | awk '{print $1}'Expected result
*/15Key points
- First field is minute
- */15 is a step
- 15 alone means once per hour
Notes
- Environment: POSIX awk / 模擬エントリのみ
- 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.