Iterate through an array and add new items to the array

Question

I have an array setup:

target_array=(
    "item1 -a100 -b250 -caaa"
    "item2 -a110 -cbbb -d1sa"
    "item3 -d2sa -exxx -fyyy"
)

I then iterate over the array and perform various actions:

for target_item in "${target_array[@]}"; do
    #Do Stuff Here
    #and create new items
    x=111
    y=222
    z=333
done

Inside the loop I get new variables and need to add them to the array, so I would end up with something like:

target_array=(
    "item1 -a100 -b250 -caaa -x111 -y222 -z333"
    "item2 -a110 -cbbb -d1sa -x112 -y223 -z334"
    "item3 -d2sa -exxx -fyyy -x113 -y224 -z335"
)

But how can I add these items to the array? Should I be adding them to the existing array, or creating a new array?

I'm trying to port a script from powershell where I would use an 'object' that contained items (item1) and properties (-a) with values (100). But couldn't see a Linux equivalent so an array seemed to be the next best thing.

Answer 1

Assuming you are using bash you can iterate over the array using indices, instead of values, with construct ${!array[@]}, and then just replace each element with new value:

for target_item in "${!target_array[@]}"; do
    x=111
    y=222
    z=333
    target_array["$target_item"]+=" -x$x -y$y -z$z"
done

Unfortunately it's not possible in bash to unfold index of an array element from its value.

---

In zsh you can simplify the procedure with a special so called subscript flag (i) and loop over an array normally:

for target_item in "${target_array[@]}"; do
     x=111                    
     y=222                    
     z=333
     i="${target_array[(i)$target_item]}"
     target_array[$i]+=" -x$x -y$y -z$z"
done

Answer 2

Creating a new array in the loop and then setting the original array to this new array:

target_array=(
    "item1 -a100 -b250 -caaa"
    "item2 -a110 -cbbb -d1sa"
    "item3 -d2sa -exxx -fyyy"
)

for target_item in "${target_array[@]}"; do
    # Do Stuff Here
    # and create new items
    x=111
    y=222
    z=333

    new_array+=( "$target_item -x$x -y$y -z$z" )
done

target_array=( "${new_array[@]}" )

Using /bin/sh (because I prefer the syntax required to work with $@ over bash's somewhat bulky array syntax):

set -- \
    "item1 -a100 -b250 -caaa" \
    "item2 -a110 -cbbb -d1sa" \
    "item3 -d2sa -exxx -fyyy"

for target_item do
    # Do Stuff Here
    # and create new items
    x=111
    y=222
    z=333

    set -- "$@" "$target_item -x$x -y$y -z$z"
    shift
done

The modified array is "$@".