ksh for loop

Shell Programming and Scripting
1

Any reason why this thing doesn't works in Korn Shell

for (( expr1; expr2; expr3 ))
do
..... ... repeat all statements between do and done until expr2 is TRUE Done

Rgds,
TS

2

This only works with kornshell 93, not kornshell 88.

3

And how to identify which korn shell is there on my OS?

Rgds,
TS

4

If you have a shell variable $KSH_VERSION, you are on ksh93. You can also probe for other features.

You also can try to call your ksh with --version as argument, ksh88 does not print anything

$ /opt/ast/bin/ksh --version
  version         sh (AT&T Research) 1993-12-28 s
$ /bin/ksh --version
$
5

Assuming your version of the Korn shell handles ((...)) in for loops, you've got the logic backwards.

for (( expr1; expr2; expr3 ))
do      statements...
done

executes the specified statements each time expr2 evaluates to TRUE and leaves the loop when expr2 evaluates to FALSE. For example:

for (( i=1; i<5; i++))
do    echo $i
done

produces the output:

1
2
3
4

because i<5 is true the 1st four times through the loop.