what is the syntax of while loop in shell scripting? code example

Example 1: while loop bash

while true;
do
	#code
done

Example 2: while loop shell script

#!/bin/sh

a=0

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

Example 3: for loop while loop shell functions

while check1
do
    # Loop while check1 is successful (returns 0)

    if check1
    then
        echo 'check1 was successful'
    fi

done