echo is used to print the contents of a variable or a string.

echo "Hello World"

printf is used to print the contents of a variable or a string.

printf "Hello World"

Uses of read read is used to read the contents of a variable or a string.

read -p "Enter your name: " name
echo "Hello $name"

cat is used to print the contents of a file.

cat README.md

tr is used to translate the contents of a file.

tr 'a-z' 'A-Z' < README.md

paste is used to print the contents of a file.

paste README.md

if else statements are used to execute a block of code if a certain condition is true.

if [ $a -gt $b ]; then
    echo "a is greater than b"
else
    echo "a is not greater than b"
fi

for loops are used to iterate over a list of values. Say we have a list of numbers, we can use a for loop to iterate over the list and print each number.

for i in {1..10}
do
    echo "Number is $i"
done

while loops are used to execute a block of code as long as a certain condition is true.

while [ $a -lt 10 ]
do
    echo "Number is $a"
    a=`expr $a + 1`
done

until loops are used to execute a block of code as long as a certain condition is false. until [ $a -gt 10 ]

until [ $a -gt 10 ]
do
    echo "Number is $a"
    a=`expr $a + 1`
done

case statements are used to execute a block of code based on the value of a variable.

case $a in
    1) echo "a is 1";;
    2) echo "a is 2";;
    3) echo "a is 3";;
    4) echo "a is 4";;
    5) echo "a is 5";;
    6) echo "a is 6";;
    7) echo "a is 7";;
    8) echo "a is 8";;
    9) echo "a is 9";;
    10) echo "a is 10";;
    *) echo "a is not between 1 and 10";;
esac

Functions are used to group a block of code together and to reuse the code.

function myfunc() {
    echo "Hello World"
}
myfunc

array=(1 2 3 4 5 6 7 8 9 10)
echo ${array[0]}
echo ${array[1]}
echo ${array[2]}
echo ${array[3]}
echo ${array[4]}
echo ${array[5]}
echo ${array[6]}
echo ${array[7]}
echo ${array[8]}
echo ${array[9]}

Associative arrays are used to store key value pairs.The key is the index and the value is the value.

declare -A assoc_array
assoc_array[key1]=value1
assoc_array[key2]=value2
assoc_array[key3]=value3
echo ${assoc_array[key1]}
echo ${assoc_array[key2]}
echo ${assoc_array[key3]}

Functions are used to group a block of code together and to reuse the code.

function myfunc() {
    echo "Hello World"
}
myfunc

Head is used to print the first n lines of a file.

```
head -n 5 README.md
```

Tail is used to print the last n lines of a file.

```
tail -n 5 README.md
```

grep is used to search for a pattern in a file.

grep "Hello" README.md

cut is used to extract a specific field from a file.

cut -d " " -f 1 README.md

sort is used to sort a file.

sort -n README.md

uniq is used to remove duplicate lines from a file.

uniq README.md

wc is used to count the number of lines, words and characters in a file.

wc README.md

tr is used to translate characters in a file.

tr " " "-" README.md

sed is used to edit a file.

sed "s/Hello/Hi/g" README.md

Data Types:

Example:

int=123
float=1.23
printf "Integer: %d\n" $int
printf "Float: %f\n" $float

declare is used to create a variable.

declare -i int
declare -f func
declare -a array
declare -A assoc_array

Type of shell :

1. Bash
2. Zsh

Them are both interpreted by the shell and executed by the shell. The difference is that the Bash shell is a shell that is written in the Bourne Again Shell (BASH) language, while the Zsh shell is a shell that is written in the Zsh language. The Bash shell is the default shell on most UNIX systems, while the Zsh shell is the default shell on most UNIX systems.

We show here shell scripting in the following example or bash programming. However, the same can be done in the Zsh shell. Window command prompt has also has the programming language feature. You can use loops, if else statements, functions, arrays, associative arrays, and more. Its call batch scripting.