LFCS Question #447: Real Exam Question with Answer & Explanation

Question

The correct crontab entry to execute the script chklog once per hour between 3 p.m. and 5 p.m. on Monday and Thursday each week is, which of the following?

Options

• A0 3,4,5 * * 2,5 chklog
• B0 3,4,5 * * 1,4 chklog
• C0 15,16,17 * * 1,4 chklog
• D0 15,16,17 1,4 * * chklog
• E* 15,16,17 * * 1,4 chklog

Explanation

The correct crontab entry for this schedule specifies 0 for minutes, 15,16,17 for hours (3 PM to 5 PM in 24-hour format), * * for day and month, and 1,4 for Monday and Thursday.

Common mistakes.

• A. The hours 3,4,5 represent 3 AM, 4 AM, and 5 AM, not PM, and 2,5 represent Tuesday and Friday, not Monday and Thursday.
• B. The hours 3,4,5 represent 3 AM, 4 AM, and 5 AM, not PM.
• D. Placing 1,4 in the day of month field means the script would run on the 1st and 4th of each month, not specifically on Monday and Thursday of each week.
• E. Using * in the minute field means the script would run every minute between 3 PM and 5 PM, not once per hour.

Concept tested. Crontab scheduling syntax

Reference. https://man7.org/linux/man-pages/man5/crontab.5.html

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