Bash Scripting

 

How to Create Your First Bash Scrip

touch hello_world.sh

Find the path to your bash shell.

where bash is located 

which bash

touch hello.sh

ls -al
Permission of file

#! bin bash

#! /bin/bash
echo "hello"

for execute
./hello.sh

Comment
# before line of comment
it give more information about script

++++++++++++++++++++++++++++++++++++++++++++++
when ever we define a 
Variable it can store somedata string data any no or any other kind of data

1 System variable
2 Userdefine variable

System variable

echo $BASH
echo $BASH_VERSION
echo $HOME
echo $HASH_VERSION
echo $PWD


2. USERDEFINE VARIABLE

name = Mark
echo $name
echo "this is my $name 

+++++++++++++++++++++++++


#To take the input from user

echo "enter name: "
read name
echo "entered name $name"


++++++++++++++++++

for multiple name
echo "enter name: "
read name1 name2
echo "Names: entered $name, $name1, $name2"

+++++++++++
to print on same line

read -p 'usename: 'user_var
echo "username : $user_var"

to take the input silent without displaying what you typing on the screen

read -sp 'password' : 'pass_var'
echo "password : $pass_var"

++++++++++++++++++++++++++++++++++++++++++++++

How to pass argument at the time of execution 

echo  $1 $2 $3 ' > echo $1 $2 $3 '

./hello.sh Mark Pranav John


It store in $1 Mark ....and all

+++++++++++

2nd method pass with array
array start from 0 th index

args=("$@")
echo ${args[0]} ${args[1]} ${args[2]}

++++++++++++++++++++++++++++

4) Condn Statement
synt:-

if [codn]
then
statement
fi

Ex:-
count = 10
if [$count -eq 9] / #[$count -gt 9]
then
echo "condn is true"
fi

++++++++
Integer compa oper
-eq - is equal to 
-ne - nt equal to
-ge - gret equ to
-lt - less than
-le - less than equal to
< - is less than
> - is greater than
>= - gre eql to
!= - not equl to

++++++++++++++++++++++++++


Comp

word=abc

if [$word == "abccc"]
then 
echo "codn is true"
fi