Essential Unix Commands for Beginners

To secure a data job in 2024, mastering Unix isn’t just a nice-to-have—it’s a necessity. 🎯

I am sure you already know the importance of this versatile operating system, right?

For those on their learning journey, I have a complete list of essential Unix commands for beginners at your fingertips that can make the process significantly smoother.

Instead of searching multiple sources, you can now access a comprehensive, organized command list all in one place, ensuring you have the tools you need exactly when you need them.

If you’re committed to mastering Unix and searching for a quick command reference, your search ends here.

List of Unix Commands

ls command

used to list the files and directories.

ls
ls -l
ls -a
ls -i
ls -R

pwd command

used to display the present working directory.

pwd

cd command

used to change the directory.

• cd directory_name (This command takes you directly to the folder you need to work in)

cd home/user/dir1

• cd .. (This command navigates you back to the previous directory, allowing you to backtrack through your directory structure quickly.)

cd ..

man command

used to view the manual for a specific command

man command_name
//example
man ls

mkdir command

used to create new directories

mkdir directory_name
//example
mkdir dir1

rmdir command

used to remove the directory

rmdir directory_name
//example
rmdir dir1

cal command

used to display calendar

cal (Displaying the current month)
cal -3 (Displaying the previous, current and next month)
cal -y (Displaying whole year)
cal -m (Starting the week from Monday)
cal -ym (Whole year calendar starting from Monday)

Date command

used to display dates

date
date -d 10/07/2024
date +"%a %d %b %y"

who command

used to display who is logged in

who
who -m

-m	Displaying all Information of Logged-In Users
-a	Displaying all Information of All Logged-In Users
-q	Displaying Login Names and Terminal Line Numbers
-H	Displaying Output with Headings
-b	Displaying Time of Last System Boot

echo command

used to display a line of text

echo "You are learning unix"
output: You are learning unix

echo -e "This is unix \n 2nd line"
output: this is unix
        2nd line

echo "23+56" | bc
output: 79

cat command

used to concatenate, display or append the files

• Write into the file

cat>file1
this is first line
this is second line

• Append the file

cat >> file1
this is third line added

• View the file

cat file1

• Concatenate a file

cat file1 file2 > combined_file

Pipelining

with the help of the pipe, the output of the command can be given as input to the next command.

-l	to print the line count
-w	to print the word counts
-c	to print the byte count
-m	to print the character count

cat access.log | wc

head command

used to display first ‘n’ lines from the file.

head -n filename
//example
head -2 file1

or,

cat filename | head -n
//example
cat file1 | head -2

tail command

used to display the last ‘n’ lines from the file.

tail -n filename
//example
tail -2 file1

or,

cat filename | tail -n
//example
cat file1 | tail -2

cut command

used to extract columns from each line of the file

-b	Bytes, select only these bytes.
-c	Characters, select only these characters.
-d	Delimiter, select only the basis of the delimiter provided
-f	Select only specified fields

//example1
cut -d '/" -f2 access.log

//example2
cut -d "-" -f1,2 access.log | cut -d ' ' -f 1,3

uniq command

to display the unique values

cut -d ' ' -f1,3 access.log | uniq -c

sort command

used to sort the elements in ascending or descending order

-t	to specify the delimiter
-k	to specify starting and ending columns for sorting
-r	to sort in reverse order
-n	to some kind of numerical data
-u	to some numerical data
-c	to remove the duplicate line

//example1
cut -d ' ' -f1,3 access.log | uniq -c | sort

//example2
cut -d ' ' -f1,3 access.log | uniq -c | sort -r

tr command

translating character

-d	deleting the character
-s	compressing multiple consecutive character
-c	complementing values of expression

//converts loweracase to uppercase
tr '[a-z]' '[A-Z]' < logs.txt

tr -d '[]' < logs.txt

grep command

used for searching and manipulating text patterns within files.

grep 'Inverter' access.log | tail -5

//for case insensitive search add -i
grep -i 'inverter' access.log

grep '^12' access.log

grep '8[1-9]' marks

pattern matching

*	to match zero or more occurrences of the previous character
[pqrs]	character class- to match a single character p,q,r or s
[^pqrs]	to match a single char which is not p,q,r or s
^pattern	to match the pattern at the beginning of the line
pattern$	to match the pattern as a whole line
^$	to match lines containing nothing
+	match one or more occurrences of previous char
?	match zero or one occurrence of the previous char
pattern1|pattern2	to match pattern1 or pattern2
(Fin|Eng)land	to match Finland or England

cp command

used to copy files and directories

cp [options] source destination

-i or interactive	Prompts before overwriting.
-r or -R	Recursively copies directories.
-u or update	Copies only when the source file is newer than the destination file or when the destination file is missing.
-v or verbose	Shows files being copied.
-a or archives	Preserves attributes and copies directories recursively.
-b or backup	take backup of destination

• copy a file

cp file1.txt file2.txt

• copying multiple files into directory

cp file1.txt file2.txt file3.txt /path/to/destination/

mv command

to move or rename files. Like cp command, it will moved to the destination location but the source copy is deleted

• -b or –backup
• -i or –interactive
• -u or update
• -n or -no-clobber

mv file1.txt /backup_dir/file2.txt

Access Permissions

Types of Permissions

1. Read (r): Allows viewing the contents of the file or directory.
2. Write (w): Allows modifying the contents of the file or directory.
3. Execute (x): Allows executing the file or accessing the directory.

Permission Categories

Permissions are assigned to three categories of users:

1. Owner (u): The user who owns the file or directory.
2. Group (g): The group that owns the file or directory.
3. Others (o): All other users.

Viewing the permission

ls -l filename
//output
-rwxr-xr--

	rwx
0	000	—
1	001	–x
2	010	-w-
3	011	.wx
4	100	r–
5	101	r-x
6	110	rw-
7	111	rwx

Changing the permission

to change the permission “chmod” is used

-R	to change the file and directory permissions recursively
–reference	to use the permission of the first argument as a reference to set permission of remaining arguments

chmod -R 755 /home/user1

chmod -R ugo+x /home/user1/app_dir

Working with an editor

In VI editor, there is 3 mode:

• command mode

When you enter the VI editor default you will be in command mode.

• insert mode(interpreted as raw text)

To insert text into the file, you need to switch to ‘VI’ insert mode.

you can type text into the file or use arrow keys to navigate

(n)h	move n position left
(n)j	move n lines down
(n)k	move n lines up
(n)l	move n position right
$	move to end of current line

Operations with insert mode

i	insert data before cursor
I	insert data at start of current line
a	insert data after cursor
A	insert data at end of current line
o	starts a new line after cursor
O	starts a new line before cursor

• escape mode(keys are interpreted for saving/exit purpose)

After insert mode, if you press ESC you will enter into command mode. On typing a ‘:’ you can enter into escape mode andgve command to save and quit the editor.

To save and quit the VI editor

:w	save changes
:wq	save changes and exit
:q	exit from editor
:q!	exit from editor and discard changes made

Closing Words

These essential Unix commands are where you begin your journey with the command line.

Regular practice will boost your confidence in using them effectively.

For detailed Unix commands, you can reference the websites like geeksforgeeks.

I hope you found this helpful!

Feel free to leave any questions or suggestions in the comments below.

Enjoy learning and exploring!✨