'*' vs. '@' in Korn Shell Array Variables

Shell Programming and Scripting
1

In order to use the shellcurses functions described at:

Shell Curses function library

I am learning about ksh, which has arrays. My trusty Kochan & Wood book says that for any Korn Shell array AR :

${AR
[*]} expands to all the defined array elements, and

${#AR
[*]} expands to the number of array elements.

But the example programs from the above website use '@' instead of '*' in the two expressions above. Both seem to work. My sample program:

#!/usr/bin/ksh93.att
source /home/lc25487/ksh/shellcurses.ksh
 
MENU[0]="First Menu Line"
MENU[1]="Second Menu Line"
MENU[2]="Third Menu Line"
ITEMCNT=${#MENU[@]}
ITEMCNTSTAR=${#MENU
[*]}
ALLITEMS="${MENU[@]}"
ALLITEMSSTAR="${MENU
[*]}"
echo
echo ITEMCNT = $ITEMCNT
echo ITEMCNTSTAR = $ITEMCNTSTAR
echo ALLITEMS = $ALLITEMS
echo ALLITEMSSTAR = $ALLITEMSSTAR
echo

produces the following output (on AIX 6.1):

==========
lipossrp01ga:/home/lc25487/ksh $ ./t2.ksh

ITEMCNT = 3
ITEMCNTSTAR = 3
ALLITEMS = First Menu Line Second Menu Line Third Menu Line
ALLITEMSSTAR = First Menu Line Second Menu Line Third Menu Line

lipossrp01ga:/home/lc25487/ksh $

What (if anything} is the difference between the usage of @ or * ?

2

Hi.

The best definition I could find:

1 Like
3

Thanks Scott, that sounds reasonable, it's kind of like the difference between $* and $@ in the Bourne shell. I'm guessing that there is no difference whatsoever between the two expressions for the number of array elements.

4

It turns out that the korn shell also has array constructs that supply the indices of an array, from 0 up to the largest defined element, either all-at-once or one-at-a-time in a loop.

For an array AR, ${!AR
[*]} expands to the string "0 1 2 .. N" . So does the construct ${!AR[@]} but this latter povides one subscript at a time in a 'for' loop, while the former consrtruct feeds everything at once. I have expanded my test program:

#!/usr/bin/ksh93.att
 
MENU[0]="First Menu Line"
MENU[1]="Second Menu Line"
MENU[2]="Third Menu Line"
 
ITEMCNT=${#MENU[@]}
ITEMCNTSTAR=${#MENU
[*]}
ALLITEMS="${MENU[@]}"
ALLITEMSSTAR="${MENU
[*]}"
BANGCNT="${!MENU[@]}"
BANGCNTSTAR="${!MENU
[*]}"
 
echo
echo ITEMCNT = $ITEMCNT
echo ITEMCNTSTAR = $ITEMCNTSTAR
echo ALLITEMS = $ALLITEMS
echo ALLITEMSSTAR = $ALLITEMSSTAR
echo BANGCNT = $BANGCNT
echo BANGCNTSTAR = $BANGCNTSTAR
echo
 
echo For Loop for ALLITEMS
echo =================
for STR in "${MENU[@]}"
do
    echo $STR
done
 
echo
echo For Loop for ALLITEMSSTAR
echo =====================
for STR in "${MENU
[*]}"
do
    echo $STR
done
 
echo
echo For Loop for BANGNT
echo ===============
for STR in "${!MENU[@]}"
do
    echo $STR
done
 
echo
echo For Loop for BANGNTSTAR
echo ===================
for STR in "${!MENU
[*]}"
do
    echo $STR
done
echo

When I run it I now get:

 
lipossrp01ga:/home/lc25487/ksh $ ./t2.ksh
 
ITEMCNT = 3
ITEMCNTSTAR = 3
ALLITEMS = First Menu Line Second Menu Line Third Menu Line
ALLITEMSSTAR = First Menu Line Second Menu Line Third Menu Line
BANGCNT = 0 1 2
BANGCNTSTAR = 0 1 2
 
For Loop for ALLITEMS
=================
First Menu Line
Second Menu Line
Third Menu Line
 
For Loop for ALLITEMSSTAR
=====================
First Menu Line Second Menu Line Third Menu Line
 
For Loop for BANGNT
===============
0
1
2
 
For Loop for BANGNTSTAR
===================
0 1 2
 
lipossrp01ga:/home/lc25487/ksh $