Interpret a line in a user's crontab edited with crontab -e.
30 2 * * * /home/alice/bin/backupWhen does this job run?
User crontab fields are minute, hour, day of month, month, and day of week, followed by the command.
Detailed explanation
Correct. Minute 30 and hour 2 mean 02:30 each day when the other fields are wildcards.
Correct. Minute 30 and hour 2 mean 02:30 each day when the other fields are wildcards.
Incorrect. Cron has no 30 o'clock and the field order is wrong.
Incorrect. Cron has no 30 o'clock and the field order is wrong.
Incorrect. Standard cron has no seconds field.
Incorrect. Standard cron has no seconds field.
Incorrect. The day-of-month field is a wildcard in this line.
Incorrect. The day-of-month field is a wildcard in this line.
Try it yourself
An example you can run in a temporary verification environment.
printf '%s\n' '30 2 * * * /home/alice/bin/backup' | awk '{print "minute="$1, "hour="$2}'Expected result
minute=30 hour=2Key points
- First field minute
- Second field hour
- No seconds field
Notes
- Environment: awk / 合成crontab行
- 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.