Some important Linux commands with examples

Linux

This article is all about some important Basic Linux commands with examples. Here we learn many of the commands such as command for adding local user, command for delete local user, grant file permissions to a file, change group ownership of a file, adding a new group, commands for information gathering about operating system, commands for creating files and folders, commands for change ownership of a file and so on. Generally, these all commands are works on all the Linux distributions same as given below. No further change is done in these commands to do so work on any of the Linux distribution which is present on the internet. So here we learn how to execute these given commands on our Linux operating system with ease.

Also Read: Some useful commands for list files and directories in the Linux {ls commands}

some important command for Linux

adduser

The adduser command is used to add a new user to a system. For example to add a new user Satish, execute the following command:

[email protected]:~# adduser satish
Adding user `satish' ...
Adding new group `satish' (1004) ...
Adding new user `satish' (1003) with group `satish' ...
Creating home directory `/home/satish' ...
Copying files from `/etc/skel' ...
Enter new UNIX password:

addgroup

The addgroup command is used to add a new group to a system. For example to add a group named as Satish, execute the following command:

[email protected]:~# addgroup satish
Adding group `satish' (GID 1004) ...
Done.

arch

The arch command is used to print the architecture of the machine. For example:

[email protected]:~# arch
i686

cal/ncal

The cal and ncal both commands are used to display a calendar on the screen as an output, but cal command display the calendar in a horizontal manner and ncal command displays the calendar in a vertical manner. For example:

[email protected]:~# cal
July 2017
Su Mo Tu We Th Fr Sa
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31
[email protected]:~# ncal
July 2017
Su 2 9 16 23 30
Mo 3 10 17 24 31
Tu 4 11 18 25
We 5 12 19 26
Th 6 13 20 27
Fr 7 14 21 28
Sa 1 8 15 22 29

cat

The cat command is used to join two files together, and print the data of these files on the standard output. It means this command prints the information which is provided to it, whether in the standard input form or form of a file. For example to print the output of a.txt file, execute the following command:

[email protected]:~# cat a.txt
Hi..what are you doing?

cd

The cd command is used to change the present working directory(pwd) of a user. For example, to go to the music directory from root directory, execute the following command:

[email protected]:~# cd Music
[email protected]:~/Music#

chgrp

The chgrp command is used to change the group ownership of a file. In this command the first argument will be new group name and the second argument will be the name of the file. For example, to change the group ownership of an a.txt file to root, execute the following command.

[email protected]:~# chgrp root a.txt

chmod

The chmod command is used to change access permissions of a file. You can give permission to a file using the numeric method and alphabetic method. Here r stands for reading permission, w stands for writing permission, and x stands for execute permission. We explain this command in detail in my earlier articles. So follow our blog for updates and stay updated.

[email protected]:~# chmod 777 rahul.txt
[email protected]:~# chmod rwx satish.txt

chown

The chown command is used to change the ownership and group of a file. For example, if you want to change the ownership of file a.txt to root and set its group as root, then execute the following command:

[email protected]:~# chown root:root a.txt

cksum

The cksum command is used to prints the CRC checksum and byte count for the input file. For example to print the CRC checksum and byte count for the a.txt file, execute the following command:

[email protected]:~# cksum a.txt
1226195471 17 a.txt

clear

The clear command is used to clear the terminal screen.

[email protected]:~# clear

cmp

The cmp command is used for byte-by-byte comparison of two files. For example, to compare a.txt and b.txt file, execute the following command:

[email protected]:~# cmp a.txt b.txt
a.txt b.txt differ: byte 2, line 1

Here, instead of a.txt and b.txt you can use your file name.
comm

The comm command is used to compare two sorted files line-by-line. For example, if file1 contains numbers 1 to 4 and file2 contains number 3 to 6 then on executing the comm command you will get:

[email protected]:~# comm a.txt b.txt
1
2
3
4
5
6

Here, a.txt and b.txt will be your file1 and file2 name.

Also Read: Files and Folder management commands in Linux Part 1 (File and folder creation)

cp

The cp command is used to copy files and directories. from one place to another place example given below.

[email protected]:~# ls
a.txt Desktop Documents Downloads Music Pictures Public Templates Videos
[email protected]:~# cp a.txt Desktop/
[email protected]:~# cd Desktop/
[email protected]:~/Desktop# ls
a.txt rahl
[email protected]:~/Desktop#

csplit

The csplit command is used to split a file into sections determined by context lines.

[email protected]:~# csplit a.txt 1 5 10
0
38
76
24

The output of this command is shown by executing ls command on your system which is given below.

[email protected]:~# ls
a.txt Desktop Documents Downloads Music Pictures Public Templates Videos <strong>xx00 xx01 xx02 xx03</strong>

date

The date command is used to show the system date and time.

[email protected]:~# date
Thu Jul 13 22:14:16 IST 2017

dd

The dd command in Linux is used for clone one hard disk to another hard disk. The dd command stands for “Disk Duplicator” and used for converting and copying data. This is very useful and dangerous tool for Linux operating system. Because it can use in many ways other than cloning of the hard disk. So we learn dd command in a detailed way in upcoming articles. Here the main use of dd command is given below that is cloning of hard disk.

[email protected]:~# dd if=/dev/sda of=/dev/sdb

df

The df command is used to display the system disk space usage in output.

[email protected]:~# df /dev/sda
Filesystem 1K-blocks Used Available Use% Mounted on
udev 4078324 0 4078324 0% /dev

diff

The diff command is used to compare two file line by line in Linux operating system.

[email protected]:~# diff a.txt b.txt
1,12c1,5
&lt; hiii
&lt; hello
&lt; how are you
&lt; what the hell?
&lt; i am fine
&lt; what about you
&lt; What the hell are going on here
&lt; I think
&lt; Its enough
&lt; For today
&lt; Rahul
&lt; Hackgyd
---
&gt; good morning
&gt; everyone
&gt; once again
&gt; i am here
&gt; with a new article
[email protected]:~#

diff3

The diff3 command is used to compare three files line by line as the name suggests.

[email protected]:~# diff3 a.txt b.txt c.txt
====
1:1,12c
hiii
hello
how are you
what the hell?
i am fine
what about you
What the hell are going on here
I think
Its enough
For today
Rahul
Hackgyd
2:1,5c
good morning
everyone
once again
i am here
with a new article
3:1,3c
hii
everyone goodmorning

dir

The dir command is used to list the directory contents. For example

[email protected]:~# dir
Desktop Music Templates Downloads
Documents Pictures satish Videos

dirname

The dirname command strips the last part of a given filename. This command removes the trailing/component from the NAME and prints the remaining portion. If it prints ‘.’ that means current directory.

[email protected]:~# dirname Desktop/
.
[email protected]:~# dirname Desktop/a.txt
Desktop

dmidecode

The dmidecode command is used to prints the system’s DMI table contents in a human-readable format. This command is also used for getting Hardware information. For example:

[email protected]:~# dmidecode
# dmidecode 3.1
Getting SMBIOS data from sysfs.
SMBIOS 2.5 present.
10 structures occupying 449 bytes.
Table at 0x000E1000.

Handle 0x0000, DMI type 0, 20 bytes
BIOS Information
Vendor: innotek GmbH
Version: VirtualBox
Release Date: 12/01/2006
Address: 0xE0000
Runtime Size: 128 kB
ROM Size: 128 kB
Characteristics:
ISA is supported
PCI is supported
Boot from CD is supported
Selectable boot is supported
8042 keyboard services are supported (int 9h)
CGA/mono video services are supported (int 10h)
ACPI is supported

Handle 0x0001, DMI type 1, 27 bytes
System Information
Manufacturer: innotek GmbH
Product Name: VirtualBox
Version: 1.2
Serial Number: 0
UUID: 0E321BAC-7BA8-42F9-8DC0-599A50AF29F9
Wake-up Type: Power Switch
SKU Number: Not Specified
Family: Virtual Machine</pre>
<pre>Handle 0x0008, DMI type 2, 15 bytes
Base Board Information
Manufacturer: Oracle Corporation
Product Name: VirtualBox
Version: 1.2
Serial Number: 0
Asset Tag: Not Specified
Features:
Board is a hosting board
Location In Chassis: Not Specified
Chassis Handle: 0x0003
Type: Motherboard
Contained Object Handles: 0

Handle 0x0003, DMI type 3, 13 bytes
Chassis Information
Manufacturer: Oracle Corporation
Type: Other
Lock: Not Present
Version: Not Specified
Serial Number: Not Specified
Asset Tag: Not Specified
Boot-up State: Safe
Power Supply State: Safe
Thermal State: Safe
Security Status: None

Handle 0x0007, DMI type 126, 42 bytes
Inactive

Handle 0x0005, DMI type 126, 15 bytes
Inactive

Handle 0x0006, DMI type 126, 28 bytes
Inactive

Handle 0x0002, DMI type 11, 7 bytes
OEM Strings
String 1: vboxVer_5.2.4
String 2: vboxRev_119785

Handle 0x0008, DMI type 128, 8 bytes
OEM-specific Type
Header and Data:
80 08 08 00 BE 61 29 00

Handle 0xFEFF, DMI type 127, 4 bytes
End Of Table

Also Read: Files and folder management in Linux part 2 {File Types}

du

The du command is used to displays the disk usages of files which is present in a directory as well as its sub-directories. For example:

[email protected]:~# du
8 ./.config/evolution/sources
12 ./.config/evolution
4 ./.config/goa-1.0
4 ./.config/systemd/user/sockets.target.wants
4 ./.config/systemd/user/default.target.wants
12 ./.config/systemd/user
16 ./.config/systemd
4 ./.config/enchant
8 ./.config/dconf
8 ./.config/gedit
4 ./.config/ibus/bus
8 ./.config/ibus
4 ./.config/gnome-session/saved-session
8 ./.config/gnome-session
84 ./.config/pulse
8 ./.config/nautilus
172 ./.config
4 ./Downloads
44 ./.vnc
4 ./Music
4 ./Pictures
624 ./.cache/gnome-software/3.26/extensions
96 ./.cache/gnome-software/3.26/ratings
724 ./.cache/gnome-software/3.26
728 ./.cache/gnome-software
936 ./.cache/gstreamer-1.0
4 ./.cache/evolution/sources/trash
8 ./.cache/evolution/sources
4 ./.cache/evolution/addressbook/trash
8 ./.cache/evolution/addressbook
4 ./.cache/evolution/calendar/trash
8 ./.cache/evolution/calendar
4 ./.cache/evolution/mail/trash
8 ./.cache/evolution/mail
4 ./.cache/evolution/memos/trash
8 ./.cache/evolution/memos
4 ./.cache/evolution/tasks/trash
8 ./.cache/evolution/tasks
52 ./.cache/evolution
4 ./.cache/obexd
4 ./.cache/folks/avatars
8 ./.cache/folks
9176 ./.cache/tracker
4 ./.cache/gnome-calculator
60 ./.cache/thumbnails/large
64 ./.cache/thumbnails
4 ./.cache/libgweather
10996 ./.cache
4 ./.gconf
4 ./Templates
4 ./Videos
4 ./.gnupg/private-keys-v1.d
8 ./.gnupg
24 ./Desktop/rahl
32 ./Desktop
4 ./Public
4 ./Documents
4 ./.local/share/evolution/addressbook/trash
4 ./.local/share/evolution/addressbook/system/photos
92 ./.local/share/evolution/addressbook/system
100 ./.local/share/evolution/addressbook
4 ./.local/share/evolution/calendar/trash
8 ./.local/share/evolution/calendar/system
16 ./.local/share/evolution/calendar
4 ./.local/share/evolution/mail/trash
8 ./.local/share/evolution/mail
4 ./.local/share/evolution/memos/trash
8 ./.local/share/evolution/memos
4 ./.local/share/evolution/tasks/trash
8 ./.local/share/evolution/tasks
144 ./.local/share/evolution
8 ./.local/share/gnome-shell
4 ./.local/share/sounds
12 ./.local/share/keyrings
4 ./.local/share/applications
76 ./.local/share/gvfs-metadata
4 ./.local/share/folks
436 ./.local/share/tracker/data
440 ./.local/share/tracker
4 ./.local/share/nautilus/scripts
8 ./.local/share/nautilus
4 ./.local/share/gnome-settings-daemon
988 ./.local/share/app-info/xmls
992 ./.local/share/app-info
4 ./.local/share/icc
1712 ./.local/share
1716 ./.local
13060 .

echo

The echo command is used to display the content which is given to it as a input text. For example:

[email protected]:~# echo hello dear
hello dear

eject

The eject command is used to eject the removable disk such as floppy disk, and CD ROM.

[email protected]:~# eject

env

The env command is used for print a list of the current environment variables, or to run another program in custom environment without modifying the current one.

[email protected]:~# env
LS_COLORS=rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=00:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;
31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:
*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.zst=01;31:*.tzst=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;
31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.wim=01;31:*.swm=01;31:*.dwm=01;31:*.esd=01;31:*.jpg=01;
35:*.jpeg=01;35:*.mjpg=01;35:*.mjpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:
*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.
nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:
*.ogv=01;35:*.ogx=01;35:*.aac=00;36:*.au=00;36:*.flac=00;36:*.m4a=00;36:*.mid=00;36:*.midi=00;36:*.mka=00;36:*.mp3=00;36:*.mpc=00;36:*.ogg=00;36:*.ra=00;36:*.wav=00;36:*.oga=00;36:*.opus=00;36:
*.spx=00;36:*.xspf=00;36:
SSH_CONNECTION=192.168.225.131 21528 192.168.225.211 22
LANG=en_US.UTF-8
S_COLORS=auto
XDG_SESSION_ID=4
USER=root
PWD=/root
HOME=/root
SSH_CLIENT=192.168.225.131 21528 22
SSH_TTY=/dev/pts/0
MAIL=/var/mail/root
TERM=xterm
SHELL=/bin/bash
SHLVL=1
LOGNAME=root
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/0/bus
XDG_RUNTIME_DIR=/run/user/0
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
_=/usr/bin/env
OLDPWD=/root/Desktop

exit

The exit command is used to close the terminal box.

[email protected]:~# exit

expand

This command is used for copies files to the standard output because expand will produce the content of the file in output with only tabs changed to spaces.

[email protected]:~# expand a.txt
hiii
hello
how are you
what the hell?
i am fine
what about you
What the hell are going on here
I think
Its enough
For today
Rahul
Hackgyd

expr

The expr command is used to evaluate the arithmetic expression. for example:

[email protected]:~# expr 5 + 4
9

factor

The factor command is used to express the prime factor of input number. for example:

[email protected]:~# factor 544
544: 2 2 2 2 2 17

fgrep

This command is used for searching a string instead of searching for a pattern that matches an expression in a file.

[email protected]:~# fgrep "hello" a.txt
hello

find

The find command is used to search any files in a directory and in its subdirectories. For example:

[email protected]:~# find . -name a.txt
./a.txt
./Desktop/a.txt

fmt

This command is a formatter for simplifying and optimizing text files.

[email protected]:~# fmt a.txt
hiii hello how are you what the hell? i am fine what about you What
the hell are going on here I think Its enough For today Rahul Hackgyd

fold

The fold command is used to wrap each input line to fit in specified width. For example:

[email protected]:~# fold -w 12
hi my name is satish meena.
hi my name i
s satish mee
na.

Also Read: Files and folder management in Linux part 3 {File Security}

free

The free command is used to display the amount of free memory and used memory in the system. For example:

[email protected]:~# free
total used free shared buff/cache available
Mem: 8182472 771524 6685192 152492 725756 6617384
Swap: 0 0 0

groups

The groups command is used to displays the name of the groups a user is part of.

[email protected]:~# groups
root

gzip

The gzip command is used to compress the input file, and replace the input file itself with having a .gz extension.

[email protected]:~# gzip b.txt

gunzip

The gunzip command is used to restored the compressed file into their original form.

[email protected]:~# gunzip b.txt.gz

head

The head command is used to displays the only first ten lines of the file to standard output. For example:

Sample output of a file

[email protected]:~# cat a.txt
hiii
hello
how are you
what the hell?
i am fine
what about you
What the hell are going on here
I think
Its enough
For today
Rahul
Hackgyd

Output of a file after using head command. Here you can observe that only first 10 lines are shown as the output of the file.

[email protected]:~# head a.txt
hiii
hello
how are you
what the hell?
i am fine
what about you
What the hell are going on here
I think
Its enough
For today

THAT’S IT

These all commands are used in Linux Operating systems same as given above. But here we only learn basic usage of these commands for deep knowledge of these commands read upcoming articles. If you found this article helpful for you then share this with your friends and if you have any queries regarding this then simply solved out your queries with the help of comment section. Also, follow our blog for further updates.

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