Dazed and confused...need help Post: 303028827

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Top Forums Shell Programming and Scripting Dazed and confused...need help Post 303028827 by alteruniverse on Tuesday 15th of January 2019 05:03:54 PM

01-15-2019

Registered User

Dazed and confused...need help

I have one script - two versions; these are test scripts to solve my problem/issue.
The difference between the two scripts is that the "for....loop" in script 'loop1' uses a variable ($xlim) to control the loop; whereas in script 'loop2' the loop parameter are fixed integers.

'loop1'
-------------------------------------------------------

Code:

#!/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

-------------------------------------------------------------
OUTPUT:
===================================

Code:

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

===================================

'loop2'
------------------------------------------------------------

Code:

#!/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

---------------------------------------------------------------------

OUTPUT
=====================================

Code:

$ 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

=====================

Of course, my actual script needs a 'parametric loop' like in script 'loop1'.
So why if one of the loop parameters is not a 'static' (constant) value does "I = {1..5}" and not "I = 1", i.e why does $i substitute to "{1..5}"?

I have not been able to find any help otherwise and would appreciate any advice!

Last edited by vgersh99; 01-15-2019 at 06:14 PM..

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