Shell Programming and Scripting

#!/bin/bash

#Just trying to check if letters are in the user input. Any tips?
# I have tried regexp and using 0-9 etc, i cannot get this to work either in just an if statement or while in a loop.

echo "Please pick a number"
read num
if [ -z $num ]; then
	echo "Please enter a number"
	read num
elif [[ $num != [[:digit:]] ]]; then
	echo "That is not a number, try again!"
	read num
# I have tried [0-9] etc and does not work.

elif	[[ $num = [[:digit:]] ]]; then
	echo $num
	echo "This is a number"
fi

# i understand this would need to be in a loop to continuously check until a number is chosen
# as of now it is always returning "That is not a number, try again!"
# I have an entire guessing working until i put anything that tries to verify if user input has letters.  If letters are present, i will be prompting for them to enter numbers within the loop.

#!/bin/bash
echo "Please pick number"
read number

if [ -z $number ]; then
echo "Please input a number"
read number

elif [[ ! $number == [0-9] ]]; then
echo "Not a number, Try again!"
read number

elif
[[ $number == [0-9]; then
echo $number
echo "That is a number!"
fi

# I can only check the first digit, how can i check the entire $number variable for any letters?

[[ $number == *[!0-9]* ]]

[[ $number =~ [^0-9] ]]

[[ $number == *[[:alpha:]]* ]]

[[ $number =~ [[:alpha:]] ]]

#!/bin/bash
win=no
echo "Please pick a number"
read number
while [ $win = no ]; do
if [ -z $number ]; then
echo "Please input a number"
win=no
read number
elif [[ "$number" == +([0-9]) ]]; then
echo "That is a number, Good Job!"
win=yes
elif [[ $number == +([[:alnum:]]) ]]; then
echo "That is not a number"
win=no
echo "Please input a number"
read number
fi
done

while [ ${win:-no} = "no" ]
  do    read -p"Pls enter number: " NMB
        if [[ "$NMB" =~ [^+-.[:digit:]] ]]
          then  echo "Not a number"
          else  echo "That is a number, Good Job!"
                win=yes
        fi
  done

[ "${number//[0-9]}" ] && echo not a number

#!/bin/bash
# Set count to zero to track amount of guesses
# Set win=no for while loop condition
win=0
count=0
echo "What is your name?"
read name
echo "Hello, $name, welcome to the Grand Random Number Enumerator Guessing Game!"
echo "Please pick a number that will be the highest number in the game"
read number
while [[ $number != +([0-9]) ]]; do
	if [[ $number == ([[:alnum:]]) ]]; then
		echo "Please input a number"
		read number
	elif [[ $number == +([['!@#'$'%^&*()-=+']]) ]]; then
		echo "Please input a number"
		read number
	elif [[ $number == +([[:alpha:]]) ]]; then
		echo "Please put in a number"
		read number
	elif [ -z $number ]; then
		echo "Please enter a number"
		read number
	fi
done
secret=$(($RANDOM % $number + 1))
echo "You have chosen $number"
echo "I have picked a number between 1 and number"
echo "Try and guess my number!"
read guess
while [ $win = no ]; do
	if [ -z $guess ] || [[ $guess == +([[:alpha:]]) ]] || [[ $guess != +([[:digit:]]) ]] || [[ $guess == +(['!@#$%^*()_+]) ]]; then
		echo "Please enter a number"
		win=no
		read guess
	elif [ "$guess" -lt "$secret" ]; then
		echo "Higher, Please guess again"
		win=no
		count=$((count + 1))
		read guess
	elif [ "$guess" -gt "$secret" ]; then
		echo "Lower, please guess again"
		win=no
		count=$((count + 1))
		read guess
	elif [ "$guess" -eq "$secret" ]; then
		echo "WINNAH! YOU AHH WICKED SMAHT!"
		echo "It took you $count tries to guess my number"
		win=yes
	fi
done
echo "Would you like to play again?, <yes/no>"
read answer
checkagain=yes
while [ $checkagain = yes ]; do
	if [[ $answer == [Yy][Ee][Ss] ]]; then	
		exec /***/***/guessingame.sh
		checkagain=no
	elif [[ $answer == [Nn][Oo] ]]; then
		checkagain=no
		echo "YOU'RE FIRED!!!!"
		exit 0
	elif [[ $answer != ^[Yy][Ee][Ss]$ ]] || [[ $answer != ^[Nn][Oo]$ ]]; then
		checkagain=yes
		echo "Please input either "yes" or "no"
		read answer
	fi
done