702-100 Exam Dumps : Linux Professional Institute BSD Specialist

The cron job syntax consists of five fields that specify the time and date of execution, followed by the command or script to run. The fields are: minute, hour, day of month, month, and day of week. Each field can have a specific value, a range, a list, a wildcard (), or a step value. The wildcard () means any possible value for that field. The option B sets the minute field to 0 and the hour field to *, which means the script will run at the 0th minute of every hour, regardless of the day, month, or weekday. This is equivalent to once per hour. The other options are either invalid syntax or do not match the desired frequency. For example, option A sets all fields to *, which means the script will run every minute of every hour of every day, month, and weekday. Option C sets the minute field to * and the hour field to 0, which means the script will run every minute of the 0th hour, or once per day at midnight. Option D has a typo (o instead of *) and option E sets the day of month field to o, which is not a valid value. References:

• crontab - FreeBSD crontab(5) Manual Page1
• Crontab Explained in Linux [With Examples] - Linux Handbook2

The question mark (?) is a special character in regular expressions that modifies the preceding expression to match zero or one times. For example, the regular expression colou?r matches both color and colour, but not colouur or colr. The question mark is also used to make an expression non-greedy, meaning that it will match the shortest possible string instead of the longest. For example, the regular expression <.?> matches the first pair of angle brackets in a string, while <.> matches the entire string enclosed by the outermost pair of angle brackets. References:

• Regular expression - Wikipedia, section “Basic concepts”
• How to write Regular Expressions? - GeeksforGeeks, section “Special Characters”

The umask command in BSD is used to set default permissions for files or directories the user creates1. The umask value is permissions to deny, taken off whatever permissions would be given by default2. The default permission values for files are 666 (rw-rw-rw-), meaning read and write for user, group, and others3. The umask value of 022 means that the permissions to deny are 022 (—w–w-), meaning write for group and others. To calculate the default permissions for newly created files, we need to subtractthe umask value from the default permission value, using bitwise AND operation4. For example:

666 - 022 = 644 rw-rw-rw- - —w–w- = rw-r–r–

Therefore, the default permissions for newly created files with a umask of 022 are 644 (rw-r–r–), meaning read and write for user, and read for group and others.

References: 1: Umask command in Linux with examples - GeeksforGeeks 2: Different permission between directory and file with ‘umask’ - Unix & Linux Stack Exchange 3: Default File Permissions (umask) - docs.oracle.com 4: What is Umask and How to Use It {Update Default Linux File Permissions} - phoenixNAP KB