Table of Contents

• Introduction
• Navigating the Filesystem
• pwd
• ls
• cd
• Getting Help
• man / help
• Creating Deleting Moving and Copying Files
• mkdir / rmdir
• touch
• cp
• rm
• mv
• Viewing and Editing Files
• cat
• vi
• File Permissions
• chown
• chgrp
• chmod
• last
• Finding Things
• find
• which
• Pattern Matching
• grep
• Redirecting Input and Output
• echo
• printf
• Super User
• sudo
• Directory Trees Disk Usage and Processes
• df
• du
• Command History
• history
• clear
• Environment variables
• env
• Text Processing
• diff
• cmp
• Networking commands
• ping
• nslookup
• traceroute
• curl
• ifconfig
• telnet
• netstat
• hostname

Introduction

I made a list of Linux commands that, I think, are important and frequently used. The main purpose of this post is to memorize basic Linux commands and make myself more familiar with other commands I don’t often use. I would keep adding more commands as the time gose by.

Navigating the Filesystem

pwd

The pwd command stands for Present Working Directory. It shows what directory you are in. It gives us the absolute path, which means the path that starts from the root (/).

$ pwd

ls

The command ls stands for list. It shows files in the directory you are in. You can see all the hidden files by using the option “-a”. You can check other options here

$ ls [options] [file|dir]

cd

The command cd stands for Change Directory. You can go to a different directory with this command.

$ cd [options(s)] [directory]

Getting Help

man / help

The man command allows admins to format and display the user manual that’s built into Linux distributions, which documents commands and other system aspects.

$ man [command]
$ [command] --help

Creating Deleting Moving and Copying Files

mkdir / rmdir

The command mkdir and rmdir stands for Make Directory and Remove Directory respectively. Use the mkdir command to create a folder or a directory and use rmdir to delete a folder or a directory.

$ mkdir [option(s)] directoryname
$ rmdir [option(s)] directoryname

touch

The touch command is used to create a file.

$ touch file

cp

The command cp stands for Copy. It copies sourcefile to targetfile.

$ cp [option(s)] sourcefile targetfile

rm

Removes the specified files from the file system. Directories are not removed by rm unless the option -r is used.

rm [option(s)] file(s)

mv

The mv command moves, or renames, files and directories on your filesystem.

//Rename a file named source to destination.
$ mv [options] [-T] source destination

//Move _source file(s)_ to a directory named destination.
$ mv [options] source [source2 ...] destination

Viewing and Editing Files

cat

The cat command displays the contents of a file, printing the entire contents to the screen without interruption.

$ cat [option(s)] file(s)

vi

Edit a file with vi editor.

$ vi file_name

File Permissions

chown

The chown keyword stands for Change Owner. It transfers the ownership of a file to the user with the specified username.

$ chown [option(s)] username.group file(s)

chgrp

The chgrp command stands for Change Group. It transfers the group ownership of a given file to the group with the specified group name. The file owner can only change group ownership if a member of both the existing and the new group.

$ chgrp [option(s)] groupname file(s)

chmod

The chmod command stands for Change Mode. It changes the access permissions.

$ chmod [options] mode file(s)

last

It displays a list of all users logged in (and out) since that file was created.

$ last

Finding Things

find

Thefind command allows you to search for a file in a given directory. The first argument specifies the directory in which to start the search.

$ find [option(s)]

ex1)

$ find / -name my.cnf

ex2)

$ find . -type f -name "name-of-the-file"

which

The Linux which command is used to find the location of a program.

$ which <programname>

Pattern Matching

grep

The grep command is used to search text. It searches the given file for lines containing a match to the given strings or words.

$ grep 'word' [filename]

The grep keyword stands for Global regular expression print.

Options for grep

-c : This prints only a count of the lines that match a pattern
-h : Display the matched lines, but do not display the filenames.
-i : Ignores, case for matching
-l : Displays list of a filenames only.
-n : Display the matched lines and their line numbers.
-v : This prints out all the lines that do not matches the pattern
-e exp : Specifies expression with this option. Can use multiple times.
-f file : Takes patterns from file, one per line.
-E : Treats pattern as an extended regular expression (ERE)
-w : Match whole word
-o : Print only the matched parts of a matching line,
 with each such part on a separate output line.

Redirecting Input and Output

echo

The echo command displays text.

$ echo [option(s)] [string(s)]

printf

The printf command in Linux is used to display the given string, number or any other format specifier on the terminal window.

$ printf "%s\n" "Hello, World!"

Super User

sudo

The keyword sudo stands for SuperUser Do. If you want any command to be done with administrative or root privileges, you can use the sudo command.

$ sudo [command]

Directory Trees Disk Usage and Processes

df

The df keyword stands for Disk Free. This command is used to check disk space usage on a linux system. The most common usage is like below, used along with the -h flag.

$ df -h

du

The du keyword stands for Disk Usage. It shows the disk usage summary of the directory you are in.

$ du [directory]

Command History

history

The history command prints a list of previously typed commands.

$ history

clear

This command clears all the clutter on the terminal and gives you a clean window to work on.

$clear

Environment variables

env

It prints the variables of the current environment. It can be used to print a list of the current environment variables or to run another program in a custom environment without modifying the current one.

$ env [OPTION]... [-] [NAME=VALUE]... [COMMAND [ARG]...]

Text Processing

diff

The diff command analyzes two files and prints the lines that are different.

$ diff file1.txt file2.txt

cmp

The cmp command in Linux/UNIX is used to compare the two files byte by byte and helps you to find out whether the two files are identical or not.

$ cmp file1.txt file2.txt

Networking commands

ping

The ping command stands for Packet INternet Groper. It lets you check whether or not a remote host is alive and responding. More info about ping command

$ ping [OPTIONS] destination(IP/DN)

nslookup

The nslookup command stands for name server lookup. It translates a domain name to an IP address (or vice versa).

$ nslookup [OPTIONS] [IP/DN]

traceroute

The traceroute command shows the journey that a packet of information undertakes from its source to its destination.

$ traceroute [OPTIONS] destination(IP/DN)

curl

curl is a tool to transfer data from or to a server, using one of the supported protocols (HTTP, HTTPS, FTP, FTPS, SCP, SFTP, TFTP, DICT, TELNET, LDAP or FILE). The command is designed to work without user interaction.

$ curl [options / URLs]

$ curl -d "name=k-sato&email=e@example.com" -X POST URL

Great article about this command

ifconfig

ifconfig stands for `interface configuration“. It is used to view and change the configuration of the network interfaces on your system. Running the ifconfig command with no arguments, like this.

$ ifconfig

telnet

The telnet connect destination host:port via a telnet protocol if connection establishes means connectivity between two hosts is working fine.

• Click here for further information.
• How to Get Telnet for MacOS in Mojave or High Sierra

$  telnet geekflare.com 443

netstat

The netstat command allows you a simple way to review each of your network connections and open sockets.

$ netstat

hostname

It shows or sets the system’s host name.

$ hostname