Joining two arrays and then creating a variable

Shell Programming and Scripting
1

Hello all...

I'd like to create a variable from an array element from two arrays. In my search for answers I found this code for bash that joins two arrays and then started to work with it. I had got to work once and then foolishly without saving the code, I started to edit it for ksh and subsequently broke it. Now I can't get it to work again. Any suggestions?

BASH CODE >>>

#!/bin/bash

NAME=([0]="John" [1]="Mary" [2]="Fred")
SURNAME=([0]="Doe" [1]="Poppins" [2]="Flintstone")

# this gets args from command line and add them to the arrays.
# it's NOT the Right Thing, but can give you a brief idea of what to do
# You may add options, like -name "list" -surname "list" to parse the
# correct elements and insert them in the appropriated array.
for i in $@
do
# this ugly stuff inside brackets counts the number of elements
# so every new element added increases array counter.
NAME[${#NAME[@]}]=$i
SURNAME[${#SURNAME[@]}]=$i
done

# starts loop at element 0 and stops at last.
for ((i=0; i < ${#NAME[@]}; i++))
do
# echo element number, name and surname.
echo "Howdy #$i: ${NAME[$i]} ${SURNAME[$i]}"
done

<<<

What I thought I had come up with was:

MY VERSION OF THE BASH CODE >>>

NAME=("John" "Mary" "Fred")
SURNAME=("Doe" "Poppins" "Flintstone")

for i in $@
do

NAME[${#NAME[@]}]=$i
SURNAME[${#SURNAME[@]}]=$i
done

for ((i=0; i < ${#NAME[@]}; i++))
do

echo "Howdy #$i: ${NAME[$i]} ${SURNAME[$i]}"
NAME[$i]=${SURNAME[$i]}
done
echo "$John"
echo "$Mary"
echo "$Fred"

<<<

---
Carl

2

What do you want it to do? What is not working?

As far as I can see, both scripts work in both bash and ksh93.

3

Basically what I want to do is take SURNAME and assign it to NAME as a variable for each element.
This is what I have come up with... ( adding/changing - [ typeset NAME[$i]="${SURNAME[$i]}" ])

#!/bin/bash

NAME="John" "Mary" "Fred"
SURNAME="Doe" "Poppins" "Flintstone"

for i in $@
do

NAME[${#NAME[@]}]=$i
SURNAME[${#SURNAME[@]}]=$i
done

for ((i=0; i < ${#NAME[@]}; i++))
do

typeset NAME[$i]="${SURNAME[$i]}"

done

echo "$John"
echo "$Mary"
echo "$Fred"

As I mentioned in my original post I got it to work another way and couldn't replicate it again. I was just wondering if it was a fluke or another way of assigning an array I was not aware of.

A follow-up question to this is how I would approach combining the two arrays together into another single array?

example: display_name="NAME[$i] ${SURNAME[$i]}"

So that it would echo ${display_name[0]} and return "John Doe"

---
Carl

4

An example:

#!/bin/bash

NAME=( "John" "Mary" "Fred" )
SURNAME=( "Doe" "Poppins" "Flintstone" )

n=0

while [ $n -lt ${#NAME[@]} ] ; do
  DISPLAY_NAME[$n]=${NAME[$n]}" "${SURNAME[$n]}
  echo ${DISPLAY_NAME[$n]}
  let n=n+1
done

With a for loop:

#!/bin/bash

NAME=( "John" "Mary" "Fred" )
SURNAME=( "Doe" "Poppins" "Flintstone" )

n=${#NAME[@]}

for (( i=0; i<n; i++ )); do
  DISPLAY_NAME[$i]=${NAME[$i]}" "${SURNAME[$i]}
  echo ${DISPLAY_NAME[$i]}
done

Regards

5

You should quote $@.

That is non-standard syntax. To loop through all elements of an array:

for i in "${NAME[@]}"

What's the point of typeset? It is non-standard, and doesn't do anything here.

Use eval:

eval "${NAME[$i]}=\${SURNAME[$i]}"