Linux Operating System — Unit 2: Commands and Process Control

01

5 Marks Question

Explain Navigation Commands

Linux navigation commands are used to view, create, remove, list, and move between directories through the terminal. The main commands are pwd, cd, mkdir, rmdir, ls, and tree.

pwd — Print Working Directory

Shows the complete path of the current working directory.

cd — Change Directory

Moves between directories using absolute or relative paths.

mkdir / rmdir

Creates a new directory or removes an empty directory.

Common Syntax

$ pwd
$ cd /home/user/Pictures
$ mkdir mydirectory
$ rmdir mydirectory
$ ls -al
$ tree Documents

Quick Revision

Command	Function
pwd	Shows the current directory
cd	Changes the current directory
mkdir	Creates a directory
rmdir	Removes an empty directory
ls	Lists files and directories
tree	Displays directory hierarchy

In shortLinux provides navigation commands such as pwd to show the current directory, cd to change directories, mkdir to create directories, rmdir to remove empty directories, ls to list contents, and tree to display the directory hierarchy.

02

5 Marks Question

Explain File Management Commands

File management commands in Linux are used to create, view, copy, move, rename, and delete files and directories. The main commands are cat, rm, cp, mv, and touch.

cat

Creates, displays, combines, and copies text file contents.

rm

Deletes files and directories; -r and -rf remove folders recursively.

cp / mv / touch

Copy, move or rename files, and create empty files or update timestamps.

Examples

cat > filename
cat file1 file2 > file3
rm sample.txt
cp original_file new_file
mv test.txt newtest.txt
touch demo.txt

Quick reminder: cat handles file contents, rm deletes files, cp copies files, mv moves or renames files, and touch creates empty files or updates their timestamps.

03

5 Marks Question

Explain File Permissions and Ownership Commands

Linux is a multi-user operating system, so file permissions and ownership are used to protect files and directories from unauthorized access. Linux provides two levels of authorization: Ownership and Permissions.

Ownership

User (u)

The owner of the file.

Group (g)

A group of users sharing the same permissions.

Other (o)

All other users who are neither owner nor group members.

Permissions

Permission	Symbol	Value	Meaning
Read	r	4	Allows reading the file
Write	w	2	Allows modifying the file
Execute	x	1	Allows executing the file

Important Commands

chmod 764 sample.txt
chmod u+x file.txt
chmod g-w file.txt
chown faizan sample.txt
chown faizan:students sample.txt
chgrp students sample.txt
umask
umask -s
umask 0022

Remember: chmod changes permissions, chown changes owner, chgrp changes group ownership, and umask controls default permissions for newly created files and directories.

In shortLinux uses read (r), write (w), and execute (x) permissions for the user, group, and others. The commands chmod, chown, chgrp, and umask are used to manage these permissions and ownership settings.

04

5 Marks Question

Explain Common System Commands

Common system commands in Linux are used to perform basic system operations such as checking logged-in users, displaying information, getting help, viewing date and time, and clearing the terminal.

who / whoami

Shows logged-in users and the current user name.

man / echo

Provides command help and displays text output.

date / clear

Displays date and time, or clears the terminal screen.

Examples

who
whoami
man ls
echo "Hello, World!"
date +%d/%m/%Y
clear

Command	Purpose
who	Shows currently logged-in users
whoami	Shows the current user's name
man	Displays the manual/help for commands
echo	Displays text or command results
date	Displays or sets date and time
clear	Clears the terminal screen

05

5 Marks Question

Explain Text Processing Commands

Text processing commands in Linux are used to view, extract, sort, compare, transform, filter, count, and redirect text data stored in files.

head / tail

Show the beginning or end of a file.

cut / sort / cmp

Extract, order, or compare file contents.

tr / uniq / wc / tee

Translate text, remove duplicates, count data, or duplicate output.

Examples

head sample.txt
tail -f sample.txt
cut -d "," -f 2 file.txt
sort -r file.txt
cmp -s file1 file2
tr 'a-z' 'A-Z'
uniq -c file.txt
wc -l file.txt
ls | tee output.txt

Quick memory trick: head = start, tail = end, cut = extract, sort = arrange, cmp = compare, tr = transform, uniq = remove adjacent duplicates, wc = count, tee = show and save.

06

5 Marks Question

Explain Process Control Commands

A process is an instance of a program currently running in the system. Process control commands are used to view, control, move, and terminate running processes in Linux.

ps / top

Displays process status and running processes in real time.

bg / fg

Moves a process between background and foreground.

kill / nice

Terminates processes or sets their priority.

Examples

ps -e
ps -f
ps ux
bg %1
fg %1
top
kill 1234
kill -9 1234
nice -n 10 firefox

Command	Function
ps	Displays process status
bg	Resumes a process in the background
fg	Brings a process to the foreground
top	Displays running processes in real time
kill	Terminates a process
nice	Sets the priority of a process

07

5 Marks Question

Explain Job Scheduling Commands

Job scheduling in Linux is used to automatically execute commands or tasks at a specified time or under specified conditions.

at

Schedules a one-time job at a specified time.

batch

Runs a job when the system load is low.

cron / crontab

Runs recurring jobs and manages schedules.

Examples

at 10:30 PM
at now + 1 hour
batch
cron
crontab -e
crontab -l
crontab -r
0 8 * * * /home/user/script.sh

Command	Purpose
at	Schedules a one-time job at a specified time
batch	Runs a job when system load is low
cron	Service for recurring / periodic jobs
crontab	Creates and manages cron schedules

In shortUse at for one-time tasks, batch for tasks based on system load, and cron/crontab for tasks that need to run repeatedly at scheduled intervals.