Practise everyday Linux commands: files, searching, pipes, text tools, permissions and processes. Every solution has been run on Ubuntu and shows its real output.
Review first: Creating, Copying and Deleting Files, Reading Files, Pipes and Redirection, Searching Text with grep, Finding Files with find, sort, uniq, cut, tr and wc, Editing Text with sed, Working with Columns in awk, File Permissions, Processes
With one mkdir command, create site/css, site/js and site/images. Then print the folder names inside site.
Use mkdir -p with braces.
mkdir -p site/{css,js,images}
ls sitecss
images
jsCopy report.txt to archive/report-2026.txt, creating archive first, then delete the original and list archive.
echo "Sales" > report.txtmkdir -p, cp and rm.
mkdir -p archive
cp report.txt archive/report-2026.txt
rm report.txt
ls archivereport-2026.txtPrint how many lines of app.log contain ERROR.
cat > app.log <<'EOF'
09:00 INFO Server started
09:01 INFO User asha logged in
09:02 WARN Disk 80 percent full
09:03 INFO User ravi logged in
09:04 ERROR Payment failed
09:05 INFO Report created
09:06 ERROR Database timeout
09:07 INFO User asha logged out
EOFgrep -c.
grep -c ERROR app.log2Print all the lines of app.log except those with INFO.
cat > app.log <<'EOF'
09:00 INFO Server started
09:01 INFO User asha logged in
09:02 WARN Disk 80 percent full
09:03 INFO User ravi logged in
09:04 ERROR Payment failed
09:05 INFO Report created
09:06 ERROR Database timeout
09:07 INFO User asha logged out
EOFgrep -v.
grep -v INFO app.log09:02 WARN Disk 80 percent full
09:04 ERROR Payment failed
09:06 ERROR Database timeoutPrint only lines 3 to 5 of app.log.
cat > app.log <<'EOF'
09:00 INFO Server started
09:01 INFO User asha logged in
09:02 WARN Disk 80 percent full
09:03 INFO User ravi logged in
09:04 ERROR Payment failed
09:05 INFO Report created
09:06 ERROR Database timeout
09:07 INFO User asha logged out
EOFsed -n '3,5p', or head with tail.
sed -n '3,5p' app.log09:02 WARN Disk 80 percent full
09:03 INFO User ravi logged in
09:04 ERROR Payment failedUnder app, print the .log files that were last changed more than 5 days ago.
mkdir -p app/src app/logs
echo "print('hi')" > app/src/main.py
echo "x" > app/src/util.py
echo "old" > app/logs/old.log
echo "new" > app/logs/new.log
touch -d "10 days ago" app/logs/old.logfind with -name and -mtime.
find app -name "*.log" -mtime +5app/logs/old.logPrint the total number of lines in all the .py files under app.
mkdir -p app/src app/logs
echo "print('hi')" > app/src/main.py
echo "x" > app/src/util.py
echo "old" > app/logs/old.log
echo "new" > app/logs/new.log
touch -d "10 days ago" app/logs/old.logfind ... -exec cat {} +, then wc -l.
find app -name "*.py" -exec cat {} + | wc -l2Print the names and salaries of the three highest-paid people in staff.csv.
cat > staff.csv <<'EOF'
name,city,department,salary
Asha,Hyderabad,Engineering,90000
Ravi,Pune,Sales,55000
Meena,Hyderabad,Engineering,105000
Karan,Chennai,Support,42000
Divya,Pune,Engineering,88000
Arjun,Hyderabad,Sales,61000
EOFSkip the header, sort by the 4th column, and take the first three.
tail -n +2 staff.csv | sort -t, -k4 -nr | head -n 3 | cut -d, -f1,4Meena,105000
Asha,90000
Divya,88000Print how many people are in each city, largest first.
cat > staff.csv <<'EOF'
name,city,department,salary
Asha,Hyderabad,Engineering,90000
Ravi,Pune,Sales,55000
Meena,Hyderabad,Engineering,105000
Karan,Chennai,Support,42000
Divya,Pune,Engineering,88000
Arjun,Hyderabad,Sales,61000
EOFcut, sort, uniq -c, then sort -nr.
tail -n +2 staff.csv | cut -d, -f2 | sort | uniq -c | sort -nr 3 Hyderabad
2 Pune
1 ChennaiPrint the total salary for each department, sorted by name.
cat > staff.csv <<'EOF'
name,city,department,salary
Asha,Hyderabad,Engineering,90000
Ravi,Pune,Sales,55000
Meena,Hyderabad,Engineering,105000
Karan,Chennai,Support,42000
Divya,Pune,Engineering,88000
Arjun,Hyderabad,Sales,61000
EOFAn awk array indexed by $3.
awk -F, 'NR > 1 {t[$3] += $4} END {for (d in t) print d, t[d]}' staff.csv | sortEngineering 283000
Sales 116000
Support 42000In app.conf, change port=8080 to port=9090 in place, and print the file.
printf "host=localhost\nport=8080\n" > app.confsed -i.
sed -i 's/port=8080/port=9090/' app.conf
cat app.confhost=localhost
port=9090Make deploy.sh executable by its owner and readable by everyone else, and print the mode as a number.
echo "echo hi" > deploy.sh
chmod 644 deploy.shchmod 744, and stat -c %a.
chmod 744 deploy.sh
stat -c '%a' deploy.sh
./deploy.sh744
hiRun ls /etc/hostname /nothing, sending normal output to ok.txt and errors to bad.txt. Print the number of lines in each file.
> and 2>.
ls /etc/hostname /nothing > ok.txt 2> bad.txt
wc -l ok.txt bad.txt | head -n 2 1 ok.txt
1 bad.txtStart sleep 60 in the background, print running if pgrep -c sleep finds it, stop it, and print the new count.
$! is the PID of the background job.
sleep 60 &
[[ $(pgrep -c sleep) -ge 1 ]] && echo running
kill $!
sleep 0.2
pgrep -c sleeprunning
0