Basic Linux Commands

Commonly used Linux Commands

ls - List files and directories in the current directory.
cd - Change directory. You can use cd followed by a directory name or a path to navigate to a different directory.
pwd -Print the current working directory.
uname - It shows the name of the kernel
clear - It uses for clear screen
whoami - It shows the current login user name
date - It shows time and date
mkdir - Create a new directory. You can specify the directory name as an argument.
touch - Create an empty file or update the timestamp of an existing file. You can specify the file name as an argument.
df - displays the amount of disk space available on the filesystem
id - display the user ID (UID) and group ID (GID)

cp - Copy files or directories. You need to specify the source and destination file/directory names.

cp <option><source> destination

#Options:
# -r for recursive
# -v for verbose
# -f for forcefully

mv - Move or rename files or directories. You can use it to both move and rename files/directories.

mv <option><source> destination

#Options:
# -r for recursive
# -v for verbose
# -f for forcefully

rm - Remove files or directories. Be careful when using this command, as it permanently deletes files/directories.
```
rm <option><source> destination

#Options:
# -r for recursive
# -v for verbose
# -f for forcefully
```
cat - Display the contents of a file on the terminal. It helps us to list, combine and write file content to standard output.
```
#creates a new file
cat > file1.txt 
#copy the content of file1 to file2
cat file1.txt > file2.txt
```

grep - Search for a pattern in a file or a group of files.

grep <options> <search pattern> <files>

#Options:
# -i -> Ignore case during search
# -r, -R -> Search recursively
# -v -> invert match, match everything except the pattern
# -l -> List files that match the pattern
# -L -> List files that do not match the pattern
# -n -> Prefix each line of output with the line number

chmod - Change the permissions of a file or directory. You can use it to set read, write, and execute permissions for different users.
```
chmod <permission> <file/directory name>

#Set permission with numeric value
# r(read) = 4
# w(write) = 2
# x(execute) =1
```
chown - Change the owner of the file or directory.
```
chown <username> <file/directory name>
```
sudo - Execute a command with administrative privileges. It's often used to perform tasks that require root access.
man - Display the manual page for a command. It provides detailed documentation and usage instructions for various commands.
history - Show a list of previously executed commands.
top - display the top process running in the system
wget - Download files from the internet using the command line. These are just a few basic Linux commands to get you started.
useradd - To create a new user account
passwd - To create user account password
userdel - To delete user account
groupadd - For add Group account
groupdel - For delete group account

find - find command used to search and locate list of files and directories based on conditions applied

find <directory> -name <permission>

find <directory> -perm <permission>

find <directory> -user <user>

find <directory> -size -10M

locate - search a file by file name in the database, whereas the find command searches in the file system
```
find <file_name>
```

awk - searches files for text containing a pattern

awk '{action}' your_file_name.txt

#search for text that has a specific pattern
awk '/regex pattern/{action}' your_file_name.txt

#Built in Variable
# NR: Keeps a current count of the number of input records. 
# NF: Keeps a count of the number of fields within the current input record. 
# FS: Contains the field separator character which is used to divide fields on the input line.  
# RS: Stores the current record separator character. 
# OFS: Stores the output field separator, which separates the fields when Awk prints them. The default is a blank space. 
# ORS: Stores the output record separator, which separates the output lines when Awk prints them. The default is a newline character.

wc - the wc(word count) is use for the count and line numbers

#count number of lines
wc -l <directory>  
#count number of words
wc -w <directory>

head - Head command is used for to display top line of the file
```
head <directory>

head -n count <directory>
```
tail - Tail command is used for to display the bottom line of the file
```
tail<directory>

tail -n count <directory>
```

tar - tar is used to compress size or drive backup

tar -<options> <files>

#Options:
# c - for create
# x - for extract
# v - for verbose
# f - for forcefully
# t - for test
# z - for gzip
# j - for bz2
# J - for xz
# C - for specific destination

crontab - used for to execute job multiple time

#for set cron jobs
crontab -e 
#for show cron jobs of current user
crontab -l 
# removing a existing cronjob
crontab -r

sudo - sudo allows us to run a program as a different user. this command runs through root privilege.
ip addr - for showing ip address
cal - display the current month's calendar with the current date highlighted

vim - vim editor used for editing a file

# Insert mode -> i
# Quit -> q
# Save & Exit -> wq

Task:

Linux command to view what’s written in a file.

~ cat
Linux command to change the access permissions of files.

~ chmod
Linux command to check which commands you have run till now.

~ history
Linux command to remove a directory/ Folder.

~ rmdir
To create a fruits.txt file and to view the content.

~ vim fruits.txt
Add content in devops.txt (One in each line) — Apple, Mango, Banana, Cherry, Kiwi, Orange, Guava.

~ vim devops.txt and add fruits name one by one.
To show only the top three fruits from the file

~ cat devops.txt | head -3
To Show only the bottom three fruits from the file.

~ cat devops.txt | tail -3
To create another file Colors.txt and to view the content. Add content in Colors.txt (One in each line) — Red, Pink, White, Black, Blue, Orange, Purple, Grey

~ vim Colors.txt and add colors names one by one and cat Colors.txt to view the content
To find the difference between fruits.txt and Colors.txt files.

~ diff fruits.txt colors.txt

Thank You,

Abhisek Moharana

Abhisek's blog

Abhisek's blog

Basic Linux Commands

Day 3 of 90daysofdevops

Table of contents

Commonly used Linux Commands

Task: