Linux commands that you should know as a Web Developer

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Hello friends, Today in this post we will see the Linux commands that you should know as a web developer. This post will also help those who are new to Linux or if you are already familiar with Linux then it will help in brushing up your skills. Linux web servers are used widely used due to their security, low cost, open-source, etc so it is important for web developers to learn Linux commands to work with it. You could see Linux servers everywhere from AWS Cloud, Google Cloud, etc. Also, it is important to learn about shell scripts which is the programming language used in Linux so before getting into that we should understand the Linux commands. So let’s get started.

pwd— command to return the current directory where we are working in.

marish@CodeWithMarish:~$ pwd
/home/marish

ls— List all files and directories in the current working directory

marish@CodeWithMarish:~/test$ ls
file1.txt  file2.txt  test1

It has some useful options which are as follows:

-a — list all files including hidden files.

-l — long listing of file which shows permissions associated with the file, user or group to which it belongs, file size, and last modification

-t — list and sort files based on the last modification time(last modified first)

-r — reverses the sorting order

marish@CodeWithMarish:~$ ls -lrt
total 28
drwxr-xr-x 3 marish marish 4096 Jan 27 00:48 test
drwxr-xr-x 2 marish marish 4096 Jan 27 14:09 random
-rwxrw-r-- 1 marish marish   32 Jan 27 15:08 file.txt

The above command uses 3 options that we have seen.

mkdir— It will create a new directory in the current working directory

marish@CodeWithMarish:~$ mkdir test

-p — it will help in creating a child directory

Suppose we need to create a child directory, and if the parent directory does not exist, this option will help in creating a parent directory if not exists

marish@CodeWithMarish:~$ mkdir testing/test123
mkdir: cannot create directory ‘testing/test123’: No such file or directory
marish@CodeWithMarish:~$ mkdir -p testing/test123

Here, while creating directory test123 within testing we got an error since the testing directory does not exist. So we need to use option -p such that it will create a parent directory if not exists.

cd— Command to change directory

marish@CodeWithMarish:~$ cd testing
marish@CodeWithMarish:~/testing$

To move one directory up use below

marish@CodeWithMarish:~/testing$ cd ..
marish@CodeWithMarish:~$

~ — represents home directory so cd ~ will switch from the current directory to the home directory.

cat— stands for concatenate, commonly used for reading the content of the file and displaying it in the standard output system.

marish@CodeWithMarish:~$ cat file.txt
hello world

You can also create a file and write text using the below command

marish@CodeWithMarish:~$ cat > file1.txt
hello i am file1

After entering press Ctrl+c to exit.

If you want to append text to the end of the file use the below command

marish@CodeWithMarish:~$ cat >> file.txt
I am appended text
^C
marish@CodeWithMarish:~$ cat file.txt
hello world
I am appended text

mv— This command will help to move and rename files.

Below, I have moved file1.txt to the testing directory.

marish@CodeWithMarish:~$ mv file1.txt testing/
marish@CodeWithMarish:~$ cd testing
marish@CodeWithMarish:~/testing$ ls
file1.txt  test123

To rename the file we will just move the file to the same directory with the new name as shown below

marish@CodeWithMarish:~/testing$ mv file1.txt newname.txt
marish@CodeWithMarish:~/testing$ ls
newname.txt  test123

cp— Command to copy files.

marish@CodeWithMarish:~/testing$ cp newname.txt ../
marish@CodeWithMarish:~/testing$ ls
newname.txt  test123
marish@CodeWithMarish:~/testing$ cd ..
marish@CodeWithMarish:~$ ls
file.txt  newname.txt  random  test  testing

We have some useful options such as:

-r — used to copy directories

marish@CodeWithMarish:~$ cp -r testing testing2
marish@CodeWithMarish:~$ ls
file.txt  newname.txt  random  test  testing  testing2

-p — used to preserve metadata of file such as permission, modified time, owner, etc

marish@CodeWithMarish:~$ cp -p file.txt newfile.txt
marish@CodeWithMarish:~$ ls -lr

-rwxrw-r-- 1 marish marish   32 Jan 27 15:08 newfile.txt
-rwxrw-r-- 1 marish marish   32 Jan 27 15:08 file.txt

head— Returns first n lines from a file.

marish@CodeWithMarish:~/$ cat names.txt
KL Rahul
Sachin Tendulkar
Virat Kohli
Rohit Sharma
Hardik Pandya
marish@CodeWithMarish:~/$ head -n 2 names.txt
KL Rahul
Sachin Tendulkar

tail— Returns the last n lines from a file.

marish@CodeWithMarish:~/$ head -n 2 names.txt
Rohit Sharma
Hardik Pandya

chmod— Change permission for files.

marish@CodeWithMarish:~$ ls -l
total 32
-rwxrw-r-- 1 marish marish   32 Jan 27 15:08 file.txt
...
marish@CodeWithMarish:~$ chmod u=rx,g=w,o=x file.txt

marish@CodeWithMarish:~$ ls -l
total 32
-rwxrw-r-- 1 marish marish   32 Jan 27 15:08 file.txt
...

u -> user, g -> group, o -> others & r -> read, w -> write, x -> execute

You can also represent permission using octal representation.

4 — read, 2 — write, 1 — execute

adding the value will help us in combining permissions. for eg: if we we want read and write then 4+2=6

marish@CodeWithMarish:~$ chmod 475 file.txt
marish@CodeWithMarish:~$ ls -l
total 32
-r--rwxr-x 1 marish marish   32 Jan 27 15:08 file.txt
...

here in chmod 475 file.txt, first value 4 -. read which is for user, second value 7 -> read(4) + write(2) + execute(1), third value 5 -> read(4) + execute(1).

If we want to give no permissions then use 0 as below.

marish@CodeWithMarish:~$ chmod 000 file.txt
marish@CodeWithMarish:~$ ls -l
total 32
---------- 1 marish marish   32 Jan 27 15:08 file.txt

grep— searches for a specific pattern in a file and based on the option it returns the lines that are matching.

marish@CodeWithMarish:~$ grep 'K' names.txt
KL Rahul
Virat Kohli

-i — used for matching case insensitive.

marish@CodeWithMarish:~$ grep 'rohit' names.txt
marish@CodeWithMarish:~$ grep -i 'rohit' names.txt
Rohit Sharma

-w — used to match words

marish@CodeWithMarish:~$ grep -w 'Pandya' names.txt
Hardik Pandya
Krunal Pandya

-n — get line numbers matching the string/pattern.

marish@CodeWithMarish:~$ grep -n 'Pandya' names.txt
5:Hardik Pandya
6:Krunal Pandya

-c — to get the count of a number of matching string/patterns.

marish@CodeWithMarish:~$ grep -c 'Pandya' names.txt
2

-B n — to get the n lines before matching the string/pattern.

marish@CodeWithMarish:~$ grep -B 2 'Hardik' names.txt
Virat Kohli
Rohit Sharma
Hardik Pandya

find— Command to find files and directories and perform subsequent operations. To understand this better we will solve questions.

To find all files in the current directory and its subsequent child directories we use option -type to check whether it's a file or a directory after -the type we specify f means file if we want to search only directory then mention d.

marish@CodeWithMarish:~$ find . -type f

./file.txt
./newfile.txt
./testing/newname.txt
./names.txt
./test/test1/random.txt
./test/file1.txt
./test/file2.txt
./testing2/newname.txt
./newname.txt

Now we need to find all the files which have names starting with “file” for that we use option -name and then in double-quotes mention file and *(represents placeholder which can have anything).

marish@CodeWithMarish:~$ find -type f -name "file*"
./file.txt
./test/file1.txt
./test/file2.txt

To find all files which have specific permissions such as 644.

marish@CodeWithMarish:~$ find . -type f -perm 644
./names.txt

./test/file1.txt
./test/file2.txt

sort— It is used to sort the contents of files. The below example demonstrates the use of the sort command. By default, it will sort in ascending order. Use option -r if you want the content to be in reversed order.

marish@CodeWithMarish:~$ cat names.txt
KL Rahul
Sachin Tendulkar
Virat Kohli
Rohit Sharma
Hardik Pandya
Krunal Pandya
marish@CodeWithMarish:~$ sort names.txt
Hardik Pandya
KL Rahul
Krunal Pandya
Rohit Sharma
Sachin Tendulkar
Virat Kohli
marish@CodeWithMarish:~$ sort -r names.txt
Virat Kohli
Sachin Tendulkar
Rohit Sharma
Krunal Pandya
KL Rahul
Hardik Pandya

df— Command to check the amount of disk space consumed by the file system. Use -h option for human-readable format

marish@CodeWithMarish:~$ df -h /home/marish
Filesystem      Size  Used Avail Use% Mounted on
/dev/sdb        251G  2.2G  237G   1% /

If you don’t specify the file/directory then it will show all the available disk space consumption

marish@CodeWithMarish:~$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sdb        251G  2.2G  237G   1% /

tools           442G  226G  217G  52% /init

drivers         442G  226G  217G  52% /usr/lib/wsl/drivers
lib             442G  226G  217G  52% /usr/lib/wsl/lib

du— It is used to check the disk space consumed by files and directories. use -h for human-readable format. Below we have not mentioned any files or directories then it will work on files and directories in the current working directory

marish@CodeWithMarish:~$ du -h
8.0K    ./random

4.0K    ./testing/test123
12K     ./testing

4.0K    ./testing2/test123
12K     ./testing2

Suppose we need to know the total space consumed by a specific file/directory then use option -s

marish@CodeWithMarish:~$ du -sh /home/marish
136K    /home/marish

chown— Command to change owners of files/directories.

marish@CodeWithMarish:~$ ls -l
total 32
-rwxrw-r-- 1 marish marish   32 Jan 27 15:08 file.txt
-rw-r--r-- 1 marish marish   79 Jan 27 22:29 names.txt
-rwxrw-r-- 1 marish marish   32 Jan 27 15:08 newfile.txt

marish@CodeWithMarish:~$ chown root names.txt
chown: changing ownership of 'names.txt': Operation not permitted
marish@CodeWithMarish:~$ sudo chown root names.txt
[sudo] password for marish:
marish@CodeWithMarish:~$ ls -l
total 32
-rwxrw-r-- 1 marish marish   32 Jan 27 15:08 file.txt
-rw-r--r-- 1 root   marish   79 Jan 27 22:29 names.txt
-rwxrw-r-- 1 marish marish   32 Jan 27 15:08 newfile.txt

Above, I have changed the owner of names.txt from marish to root, as it is a root user command we need to execute it using sudo.

whoami— command to get the name of the currently logged-in user.

marish@CodeWithMarish:~$ whoami
marish

uname— It is used to get information about the operating system and system hardware.

marish@CodeWithMarish:~$ uname
Linux
marish@CodeWithMarish:~$ uname -o
GNU/Linux
marish@CodeWithMarish:~$ uname -r
5.4.72-microsoft-standard-WSL2
marish@CodeWithMarish:~$ uname -n
CodeWithMarish
marish@CodeWithMarish:~$ uname -m
x86_64
marish@CodeWithMarish:~$ uname -a
Linux CodeWithMarish 5.4.72-microsoft-standard-WSL2 #1 SMP Wed Oct 28 23:40:43 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

Above, uname without option will return kernel name. The description for options is as follows.

-o — to get the name of the operating system

-r — to get kernel release

n — to get the hostname

-m — to get the architecture of the system

- a — if you don’t remember all the options, just use -a it will return all the information such as kernel name, hostname, kernel release, kernel version, architecture, os name

free— It displays the amount of free memory space available in the system along with the used memory space. use option -h for human-readable format.

marish@CodeWithMarish:~$ free -h
              total        used        free      shared  buff/cache   available
Mem:          3.8Gi        75Mi       3.7Gi       0.0Ki        59Mi       3.6Gi
Swap:         1.0Gi          0B       1.0Gi

top— List all the running Linux processes and other information such as load average, CPU & memory used, etc. It also shows the process in real-time.

top - 07:48:01 up 31 min,  0 users,  load average: 0.00, 0.00, 0.00
Tasks:   5 total,   1 running,   4 sleeping,   0 stopped,   0 zombie
%Cpu(s):  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
MiB Mem :   3873.0 total,   3736.4 free,     76.8 used,     59.7 buff/cache
MiB Swap:   1024.0 total,   1024.0 free,      0.0 used.   3653.1 avail Mem

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU  %MEM     TIME+ COMMAND
    1 root      20   0    1740   1084   1016 S   0.0   0.0   0:00.05 init
    7 root      20   0    1760     72      0 S   0.0   0.0   0:00.00 init
    8 root      20   0    1760     88      0 S   0.0   0.0   0:00.10 init
    9 marish    20   0   10052   4996   3280 S   0.0   0.1   0:00.13 bash
   91 marish    20   0   10864   3740   3228 R   0.0   0.1   0:00.10 top

lsof— Displays a list of all open files.

marish@CodeWithMarish:~$ lsof
COMMAND PID TID TASKCMD   USER   FD      TYPE DEVICE SIZE/OFF  NODE NAME

bash      9             marish  cwd       DIR   8,16     4096   664 /home/marish
bash      9             marish  rtd       DIR   8,16     4096     2 /
bash      9             marish  txt       REG   8,16  1183448  1602 /usr/bin/bash
bash      9             marish  mem       REG   8,16    51832 11403 /usr/lib/x86_64-linux

If we want to get only for a specific user use option -u and then specify username

marish@CodeWithMarish:~$ lsof -u marish
COMMAND PID TID TASKCMD   USER   FD      TYPE DEVICE SIZE/OFF  NODE NAME

bash      9             marish  cwd       DIR   8,16     4096   664 /home/marish
bash      9             marish  rtd       DIR   8,16     4096     2 /
bash      9             marish  txt       REG   8,16  1183448  1602 /usr/bin/bash
bash      9             marish  mem       REG   8,16    51832 11403 /usr/lib/x86_64-linux

htop— It is more of an interactive version of the top command which provides an additional option to search, filter, kill, etc in an interactive way.

kill — It is used to kill a process.

marish@CodeWithMarish:~$ kill process_id

lscpu— To get the CPU details of the system.

marish@CodeWithMarish:~$ lscpu
Architecture:                    x86_64
CPU op-mode(s):                  32-bit, 64-bit
Byte Order:                      Little Endian
Address sizes:                   39 bits physical, 48 bits virtual
CPU(s):                          8
...

To get the details about the operating system,

marish@CodeWithMarish:~$ cat /etc/os-release
NAME="Ubuntu"
VERSION="20.04 LTS (Focal Fossa)"
ID=ubuntu
ID_LIKE=debian
PRETTY_NAME="Ubuntu 20.04 LTS"

hostname— To get the hostname of the system. You can use -i to get the IP address of the hostname.

marish@CodeWithMarish:~$ hostname
CodeWithMarish
marish@CodeWithMarish:~$ hostname -i
127.0.1.1

ps — It is used to get all the currently running processes of the system.

marish@CodeWithMarish:~$ ps
  PID TTY          TIME CMD
    9 pts/0    00:00:00 bash
  109 pts/0    00:00:00 ps

PID — process ID, TTY = terminal type, TIME — process running time, CMD — the command that started the process

marish@CodeWithMarish:~$ ps aux
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.0   1740  1084 ?        Sl   07:16   0:00 /init
root         7  0.0  0.0   1760    72 ?        Ss   07:16   0:00 /init
root         8  0.0  0.0   1760    88 ?        S    07:16   0:00 /init
marish       9  0.0  0.1  10052  5000 pts/0    Ss   07:16   0:00 -bash
marish     128  0.0  0.0  10608  3348 pts/0    R+   08:38   0:00 ps aux

The above command will return all processes along with some additional information such as CPU and memory used.

useradd— It is used to add a new user.

marish@CodeWithMarish:~$ sudo useradd marish2

[sudo] password for marish:

passwd— Used to set the password for new users.

marish@CodeWithMarish:~$ sudo passwd marish2
New password:
Retype new password:
passwd: password updated successfully

userdel— It is used to delete a user.

marish@CodeWithMarish:~$ sudo userdel marish2

history— It is used to return all the previously executed commands.

marish@CodeWithMarish:~$ history

   1  ls

   2  ls
   3  pwd
   4  mkdir testing
   5  mkdir -p test/test1/

vmstat— It is used to get the virtual memory statistics.

marish@CodeWithMarish:~$ vmstat
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 0  0      0 3783392  19820  79028    0    0     1    45    1    3  0  0 100  0  0

wget— It is used to download files from the internet. In the below example I have downloaded the index.html file from my blogs i.e codewithmarish.com. wget requires an URL to download from so I passed the URL https://codewithmarish.com

marish@CodeWithMarish:~$ ls
file.txt  names.txt  newfile.txt  newname.txt  random  test  testing  testing2
marish@CodeWithMarish:~$ wget https://codewithmarish.com
--2022-01-29 11:58:45--  https://codewithmarish.com
Resolving codewithmarish.com (codewithmarish.com)... xx.xx.xx.xxx, xx.xxx.xxx.xx, xxx.xx.xx.x, ...
Connecting to codewithmarish.com (codewithmarish.com)|xx.xx.xx.xxx|:xxx... connected.
HTTP request sent, awaiting response... 200 OK
Length: 8553 (8.4K) [text/html]
Saving to: ‘index.html’

index.html                    100%[================================================>]   8.35K  --.-KB/s    in 0.001s

2022-01-29 11:58:46 (6.00 MB/s) - ‘index.html’ saved [8553/8553]

marish@CodeWithMarish:~$ ls
file.txt  index.html  names.txt  newfile.txt  newname.txt  random  test  testing  testing2

alias— It is used to get all shortcuts created for the command. It will be act as an proxy for a command. Suppose if we have long command which you use frequently, in this case we will create an alias for that command.

To get all aliases

marish@CodeWithMarish:~$ alias
alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'
alias egrep='egrep --color=auto'
alias fgrep='fgrep --color=auto'
alias grep='grep --color=auto'
alias l='ls -CF'
alias la='ls -A'

To create a new alias, below I have created an alias for echo “Hello World” as hello so whenever I type hello in the terminal it will execute echo “Hello World”

marish@CodeWithMarish:~$ alias hello="echo Hello World"
marish@CodeWithMarish:~$ hello
Hello World
marish@CodeWithMarish:~$ alias
alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'
alias egrep='egrep --color=auto'
alias fgrep='fgrep --color=auto'
alias grep='grep --color=auto'
alias hello='echo Hello World'

ifconfig— ifconfig ( Interface Configuration ) is used for viewing network interface configuration.

nslookup— It is used to query domain name servers.

marish@CodeWithMarish:~$ nslookup codewithmarish.com
Server:         xxx.xx.xxx.x
Address:        xxx.xx.xx.x#xx

Non-authoritative answer:
Name:   codewithmarish.com
Address: xx.xx.xx.xx
Name:   codewithmarish.com
Address: xx.xx.xx.xx
Name:   ns1.vercel-dns.com
Address: xxx.xx.xx.x
Name:   ns2.vercel-dns.com
Address: xxx.xx.xx.x

man— It is used to get the manual page for a command

marish@CodeWithMarish:~$ man ls

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