I want to access the variable array index while looping through an array in my bash shell script

myscript.sh

#!/bin/bash
AR=('foo' 'bar' 'baz' 'bat')
for i in ${AR[*]}; do
  echo $i
done

The result of the above script is.

foo
bar
baz
bat

The result I seek is.

How do I alter my script to achieve this?

Best Answer

You can do this using List of array keys . From the bash man page.

${!name[@]}
${!name[*]}

List of array keys. If name is an array variable, expands to the list of array indices (keys) assigned in name. If name is not an array, expands to 0 if name is set and null otherwise. When @ is used and the expansion appears within double quotes, each key expands to a separate word.

For your example.

#!/bin/bash
AR=('foo' 'bar' 'baz' 'bat')
for i in "${!AR[@]}"; do
  printf '${AR[%s]}=%s\n' "$i" "${AR[i]}"
done

This results in.

${AR[0]}=foo
${AR[1]}=bar
${AR[2]}=baz
${AR[3]}=bat

Note that this also works for non-successive indexes

#!/bin/bash
AR=([3]='foo' [5]='bar' [25]='baz' [7]='bat')
for i in "${!AR[@]}"; do
  printf '${AR[%s]}=%s\n' "$i" "${AR[i]}"
done

This results in.

${AR[3]}=foo
${AR[5]}=bar
${AR[7]}=bat
${AR[25]}=baz