notes/session-15.txt at main · daws-88s/notes · GitHub

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1. Create repo either in organisation or directly
2. Clone repo in laptop
3. write something
4. git add ., git add <file-name>
5. git commit -m "message"
6. git push origin main

git config --global user.name
git config --global user.email

write only in laptops
don't write in linux servers
only pull linux

95% thinking+design 5% coding

pseudo code -> no syntax, just assumption

if today is sunday, enjoy the holiday otherwise go to school

today=wednesday
if(today != sunday){
	print ("goto school")
}
else{
	print("take holiday, enjoy")
}

15

15/2 -> 1
if reminder is 0 -> even
otherwise odd

number=15
reminder=15%2
reminder=1

if(reminder == 0){
	print("even number")
}
else{
	print("odd number")
}

variables
data types
conditions
functions
loops
error handling

let x=1, y=0

derive the formula

submit finally

variables are like containers that holds something

DRY -> Dont repeat yourself
change in one place reflect everywhere you refer
easy to maintain
readable

PERSON1=Suresh
PERSON2=Ramesh

$VAR_NAME
${VAR_NAME}

sh 03-conversation.sh Suresh Ramesh
args == parameters

$1=Suresh
$2=Ramesh

I want a command to be executed and take the output into variable, how to do that?


VAR_NAME=$(command)

Special variables
=================
$1 $2 ... $N args passed to script
All variables passed to script: $@
Number of variables passed to script: $#
Script name: $0
Present which directory you are in: $PWD
Who is running this script: $USER
Home direcory of the user: $Home
PID of the script: $$
sleep 100 &
Background process id: $!
Exit status of previous command: $?

$@ vs $*
=========
$@ treats args seperately
$* treats as single args

data types
==============
variables are holding data..

mobile number -> numbers
	integers -> -33,768 -> 33,768
	float -> 45.90
	decimanl -> long number
	complex -> 4+8i
names -> string
major? -> yes or no boolean
skills -> devops aws docker kubernetes -> list of skills
skills -> map or dictionary
	devops: 4 -> key -> value
	docker: 3
	kubernetes: 2

areane4 -> 5
speed round up -> 8.2km/sec -> 8km/sec
copied code

integer speed=8km/sec
integer speed=8.2km/sec

number
string

everything is string in shell

position/index in coding starts from 0

conditions
==========

if or when

if [ expression ]; then
	code here
fi

if [ expression ]; then
	code here
elif [ expression ]; then
	code here
else
	code here
fi

EXIT code
==========
0-127

0 -> success
anything else -> failure

nginx

dnf install nginx -y

if root user then success
otherwise failure

root user id -> 0
other users -> greater than 0