bash + for loop + output index number and element

Question

This is my array:

$ ARRAY=(one two three)

How do I print the array so I have the output like: index i, element[i] using the printf or for loop I use below

1,one
2,two
3,three

Some notes for my reference

1 way to print the array:

$ printf "%s\n" "${ARRAY[*]}"
one two three

2 way to print the array

$ printf "%s\n" "${ARRAY[@]}"
one
two
three

3 way to print the array

$ for elem in "${ARRAY[@]}"; do  echo "$elem"; done
one
two
three

4 way to print the array

$ for elem in "${ARRAY[*]}"; do  echo "$elem"; done
one two three

A nothe way to look at the array

$ declare -p ARRAY
declare -a ARRAY='([0]="one" [1]="two" [2]="three")'

John Kugelman · Accepted Answer · 2016-07-27 02:37:41Z

40

You can iterate over the indices of the array, i.e. from 0 to ${#array[@]} - 1.

#!/usr/bin/bash

array=(one two three)

# ${#array[@]} is the number of elements in the array
for ((i = 0; i < ${#array[@]}; ++i)); do
    # bash arrays are 0-indexed
    position=$(( $i + 1 ))
    echo "$position,${array[$i]}"
done

Output

1,one
2,two
3,three

edited Jul 27, 2016 at 2:37

John Kugelman

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answered Jul 27, 2016 at 2:31

xxfelixxx

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Comments

LegZ · Accepted Answer · 2017-05-15 12:16:12Z

21

The simplest way to iterate seems to be:

#!/usr/bin/bash

array=(one two three)

# ${!array[@]} is the list of all the indexes set in the array
for i in ${!array[@]}; do
  echo "$i, ${array[$i]}"
done

answered May 15, 2017 at 12:16

LegZ

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Comments

helvete · Accepted Answer · 2023-12-06 08:46:29Z

1

Actually, for your shortest solution to answer exactly to the initial request, code should be :

#!/usr/bin/bash

array=(one two three)
for i in ${!array[@]}; do
  echo "$(($i+1)), ${array[$i]}"
done

... in order to print element number starting from 1, not zero.

$(($i+1)) is a Bash compound $(( )) command of "arithmetic expansion" for evaluation of arithmetic expressions.

edited Dec 6, 2023 at 8:46

helvete

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answered Dec 2, 2023 at 12:06

Gitoo22

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