Shell Programming and Scripting

#!/bin/bash

zz=3
yy=0
xlim=5

for i in {1..$xlim}; do 
   echo "I = $i"
   ((yy=$zz\*i))
   echo "Welcome $i times  $yy"
done

$ loop1
I = {1..5}
./loop1: line 9: ((: {1..5}: syntax error: operand expected (error token is "{1..5}")
Welcome {1..5} times  0

#!/bin/bash

zz=3
yy=0
xlim=5

for i in {1..5}; do 
   echo "I = $i"
   ((yy=$zz\*i))
   echo "Welcome $i times  $yy"
done

$ loop2
I = 1
Welcome 1 times  3
I = 2
Welcome 2 times  6
I = 3
Welcome 3 times  9
I = 4
Welcome 4 times  12
I = 5
Welcome 5 times  15

       A correctly-formed brace expansion must contain unquoted opening and closing braces, and at least one unquoted comma or  a
       valid sequence expression.  Any incorrectly formed brace expansion is left unchanged.  A { or , may be quoted with a back‐
       slash to prevent its being considered part of a brace expression.  To avoid conflicts with parameter expansion, the string
       ${ is not considered eligible for brace expansion.

#!/usr/bin/bash
#set -x

zz=3
yy=0
xlim=5

for i in $(eval echo {1..${xlim}}) ; do
   echo "I = $i"
   ((yy=zz * i))
   echo "Welcome $i times  $yy"
done

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

i=1
while [ "$i" -lt "$xlim" ]
do
...
        i=$((i+1))
done

$ for i in $(seq 1 5); do echo $i; done
1
2
3
4
5

Last login: Tue Jan 15 22:54:14 on ttys000
AMIGA:amiga~> x={1..5}
AMIGA:amiga~> for y in $( eval "echo ${x}" ); do echo "$y"; done
1
2
3
4
5
AMIGA:amiga~> _