To find nth position of character in string

Shell Programming and Scripting
1

Hi guyz i want to know nth position of character in string. For ex.
var="UK,TK,HK,IND,AUS"

now if we see 1st occurance of , is at 3 position, 2nd at 6,..4th at 13 position.
1st position we can find through INDEX, but what about 2nd,3rd and 4th or may be upto nth position. ?
In oracle we had instr there we could provide the nth number occurance also. Here how we can achieve it ?

FYI i am beginner in unix and i m using KSH

2

Is this a homework assignment?

What operating system and version of ksh are you using? If you don't know, show us the output from the commands:

uname -a
print ${.sh.version}
what /bin/ksh | grep Version
3

You could try this function:

function index
{
    p=1
    f=0
    t="$1"
    catch=""
    while [ $p -le ${#1} ]
    do
        if [ "${t#$2}" != "$t" ]
        then
            let f=f+1
            if [ $f -eq ${3:-1} ]
            then
                echo $p
                return
            fi
        fi
        t="${1#$catch?}"
        catch="${1%$t}"
        let p=p+1
    done
    echo 0
}

Call it like this:

index "UK,TK,HK,IND,AUS" , 4
# Result: 13

Or even this:

index "UK,TK,HK,IND,AUS" "?K" 3
# Result: 7