Append elements to an array in bash

Question

I tried the += operator to append an array in bash but do not know why it did not work

#!/bin/bash

i=0
args=()
while [ $i -lt 5 ]; do
    args+=("${i}")
    echo "${args}"
    let i=i+1
done

expected results

actual results

It does work. However, echo "${args}" only shows the first element. You need to change it to echo "${args[@]}" to output all elements — Intelligent Shade of Blue
– Intelligent Shade of Blue, Commented Mar 23, 2019 at 18:15
Slightly OT, but i=0 ... while [ $i -lt 5 ]; do ... let i=i+1 ... done can be replaced with for ((i=0; i<5; ++i)); do ... done — Intelligent Shade of Blue
– Intelligent Shade of Blue, Commented Mar 23, 2019 at 18:17
Possible duplicate: Expanding a bash array only gives the first element — wjandrea
– wjandrea, Commented Oct 17, 2022 at 20:43

wjandrea · Accepted Answer · 2020-01-07 16:05:20Z

41

It did work, but you're only echoing the first element of the array. Use this instead:

echo "${args[@]}"

Bash's syntax for arrays is confusing. Use ${args[@]} to get all the elements of the array. Using ${args} is equivalent to ${args[0]}, which gets the first element (at index 0).

See ShellCheck: Expanding an array without an index only gives the first element.

Also btw you can simplify let i=i+1 to ((i++)), but it's even simpler to use a C-style for loop. And also you don't need to define args before adding to it.

So:

#!/bin/bash
for ((i=0; i<5; ++i)); do
    args+=($i)
    echo "${args[@]}"
done

edited Jan 7, 2020 at 16:05

answered Mar 23, 2019 at 18:11

wjandrea

34k10 gold badges69 silver badges106 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

blackgreen · Accepted Answer · 2024-05-24 21:29:53Z

0

I think this is more what you're looking for ...

#! /bin/bash

for (( i = 1; i <= ${#@}; i++ ))
do
  args[${i}]="${!i}"
done

for (( i = 1; i <= ${#args[@]}; i++ ))
do
  echo "${args[${i}]}"
done

1 2 3
4 5 6

edited May 24, 2024 at 21:29

blackgreen♦

46.9k29 gold badges171 silver badges163 bronze badges

answered Mar 25, 2023 at 13:33

sysnic73

91 bronze badge

1 Comment

Community Over a year ago

Your answer could be improved with additional supporting information. Please edit to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers in the help center.

Collectives™ on Stack Overflow

Append elements to an array in bash

2 Answers 2

Comments

1 Comment

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Linked

Related