shell script to run for loop N times where N is user input

Question

#!/bin/bash

read -p "Enter X in seconds: " X
read -p "Enter M(no. of times): " M

for i in {1.."$M"};
do
    gcc hello.c -o hello
    ./hello
    sleep "$X"
done;

Shell script to run a simple hello world C code every X seconds for M times, where X and M are user input. When I run the script, for loop runs only one time. But when I replace "$M" with any number, it runs well. So what is my mistake here? How can I give user input in for loop iteration?

Answer 1

Bash's brace expansion happens before variables are evaluated. You can use the alternative C-style loop instead:

for((i=1; i<=M; i++)); do
    ....
done

Answer 2

for i in $(seq X Y); do ... done