Write a shell script which takes an input (an integer smaller than 10,000) from users and displays each digit of the integer one by one

Question

When input “153”, the shell script will identify and display “1”, “5” and “3” on the screen sequentially. If input “69”, it will display “6” and “9”.

Answer 1

Pipe user input through sed:

echo $1 | sed 's/\(.\)/\1 /g'

Answer 2

Bash treats everything as a string.

Here is a Bash way to loop character by character over a string:

s=123
for (( i=0; i<${#s}; i++ )); do
    echo "${s:$i:1}"
done

Prints:

1
2
3

Still for you to do:

1. Determine that s is a valid integer (Hint)
2. Determine that s is a string representing less than 10,000? (Hint: inside of (( double_parentesis )) Bash treats those strings as integers)

Answer 3

Does your grep support the -o option? Then

$ echo "153" | grep -o .
1
5
3

Answer 4

Another way of doing it:

#!/bin/bash

string="12345"

while IFS= read -n 1 char
do
    echo "$char"
# done <<< "$string"
done < <(echo -n "$string")

A here-string can be used instead of a < <(echo -n ...) construct if you do not care about a trailing newline.