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Linux & Shell Scripting · Question Set
Advanced Shell Commands & Automation interview questions for placements and exams.
Questions
14
Included in this set
Subject
Linux & Shell Scripting
Explore more sets
Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for Linux & Shell Scripting.
The && operator executes the next command only if the previous one succeeded. The semicolon (;) executes all commands sequentially, regardless of success or failure.
mkdir logs && cd logs
For complete preparation, combine this set with full subject-wise practice for Linux & Shell Scripting. You can also explore other subjects and sets from the links below.
The cron daemon runs scheduled commands defined in crontab files. It is used for automating backups, reports, and maintenance tasks at fixed times or dates.
crontab -e 0 2 * * * /home/user/backup.sh
crontab -l lists all scheduled cron jobs for the logged-in user. It’s useful for verifying active automation tasks or debugging missed schedules.
crontab -l
The at command is used to execute a command once at a specified time. Unlike cron, it is not repetitive and is perfect for temporary or one-time jobs.
echo 'ls /tmp' | at 11:30
The >> operator appends command output to a file without overwriting its contents. This is often used in logging to maintain persistent records.
echo 'Backup complete' >> backup.log
The -c flag in grep counts matching lines instead of printing them. This helps quickly check how many errors or warnings are present in a log file.
grep -c error /var/log/syslog
logrotate automatically rotates, compresses, and deletes old logs to prevent disk overuse. It’s configured using /etc/logrotate.conf and is essential for server maintenance.
Arguments are passed after the script name and accessed using positional parameters like $1, $2, and so on. $0 refers to the script name, and $# gives the total count of arguments.
echo 'First argument:' $1 echo 'Total args:' $#
You can check the exit status of each command using $? and use if conditions to act on failures. Adding set -e at the top stops script execution immediately when a command fails, ensuring predictable automation.
set -e cp data.txt /backup/ || echo 'Backup failed'
Crontab syntax uses five fields: minute, hour, day of month, month, and day of week. For example, 0 3 * * 1 means run every Monday at 3 AM. Using */5 in a field sets the command to repeat every 5 units.
0 3 * * 1 /scripts/cleanup.sh
You can redirect both standard output and error to a log file using > and 2> operators. For example, script.sh > output.log 2>&1 saves all messages, making debugging easier later.
./deploy.sh > deploy.log 2>&1
First, write a shell script that copies important files to a backup directory with a timestamp. Then, schedule it in crontab to run every night using a 0 2 * * * entry for 2 AM backups.
0 2 * * * /home/admin/backup.sh
Pipes can chain multiple commands together for automation. For instance, you can filter and email only failed log entries. Example: grep 'FAILED' app.log | mail -s 'Daily Errors' admin@domain.com.
grep 'FAILED' app.log | mail -s 'Daily Errors' admin@domain.com
Appending an ampersand (&) at the end of a command executes it in the background. This frees the terminal and allows multiple commands to run simultaneously.
sh long_script.sh &