Day 2 of #90 Days of DevOps :
Linux is an open-source operating system that was developed by Linus Torvalds.
What is the Linux command to
Check your present working directory
pwd
List all the files or directories including hidden files
ls -a
Create a nested directory A/B/C/D/E
mkdir -p test1/test2/test3/est4
Create a new file, touch is used when you want to create a file but it will not open in text editor mode
touch file1
To view what's written in a file
cat file1
Linux Permissions
Linux has 3 types of permissions: read, write and execute
read: to set read permission (r=4)
write: to set write permission (w=2)
execute: to set execute permission (x=1)
These permissions can be applied to user(u), group(g) and others(o).
To change the access permissions of files
chmod 777 file1
To check which commands you have run till now
history
To remove a directory/ Folder
rmdir test1
To create a fruits.txt file and to view the content
vim fruits.txt
cat fruits.txt
vim is used when the file needs to be created as well as opened as a text editor
Mostly used modes in VIM:
Normal mode: This is the default mode in which vim starts. In normal mode, you can use various commands to navigate and edit the text.
Insert mode: In insert mode, you can type text into the file. To enter insert mode, press the "i" key. To exit insert mode and return to normal mode, press the "Esc" key.
Command mode: In command mode, you can enter commands to perform various actions, such as saving the file or quitting vim. To enter command mode, press the ":" key.
Day 3 of #90 Days of DevOps:
Add content in devops.txt (One in each line) - Apple, Mango, Banana, Cherry, Kiwi, Orange, Guava
vim devops.txt
cat devops.txt
To show only the top three fruits from the file
head -3 devops.txt
This command prints the first N number of data of the given input. By default, it prints 10 lines.
To show only the bottom three fruits from the file
tail -3 devops.txt
This command prints the last N number of data of the given input. By default, it prints 10 lines.
To find the difference between fruits.txt and devops.txt file
diff fruits.txt devops.txt
To search for a particular string/ word in a text file
grep This file1
To sort the results of the search either alphabetically or numerically
sort devops.txt - It also sorts files and directories
sort -r: The flag returns the results in reverse order.
sort -f: The flag does case-insensitive sorting.
sort -n: The flag returns the results as per numerical order.
To extract specific fields or columns from a file or standard input
cut -column number-number of characters filename
cut -c1-3 devops.txt
To perform basic text transformations on an input file. It stands for "stream editor"
sed options [script] [inputfile]
sed 's/Apple/Fruit/' devops.txt
To find files and directories and perform subsequent operations on them
In the below command, It will search in the present working directory and its subdirectories, and print the name of the file that has a “.txt” file extension.
find . -name "*.txt"
free: This command displays the total amount of free space available along with the amount of memory used and swap memory in the system, and also the buffers used by the kernel
nslookup: This stands for “Name server Lookup”. This is a tool for checking DNS hostname to IP or IP to Hostname. This is very helpful while troubleshooting
