Which directory contains the shell scripts intended to run on a daily basis?

The directory that contains shell scripts intended to run on a daily basis is indeed /etc/cron.daily. This directory is specifically set up for scripts that the cron daemon executes once per day, allowing system administrators to automate tasks that need to run daily, such as system maintenance, backups, or log rotations.

When a script is placed in /etc/cron.daily, it is executed by the cron service, which manages scheduled tasks in Unix-like operating systems. The cron daemon looks into this directory and executes each script within it at a scheduled time, usually early in the morning, ensuring that these important tasks are performed on a regular basis without manual intervention.

In contrast, the other options serve different purposes: /usr/lib/cron typically contains system-wide cron configuration files and scripts, /var/spool/cron is where user-specific crontab files are stored, and /etc/cron.hourly contains scripts scheduled to run on an hourly basis. Each of these directories is designed for different frequencies of execution, thus illustrating the unique role of /etc/cron.daily in managing daily scheduled tasks.