How to pass empty string to bash for loop

Question

I want to pass an empty string as one of the values to a bash for-loop – like this:

for var in "" A B C; do
    ...
done

This works. However, I would like to store the possible values in a variable, like this:

VARS="" A B C
for var in $VARS; do
    ...

Here, the empty string is ignored (or all values are concatenated if I use for var in "$VARS"). Is there an easy way to solve this?

Etan Reisner · Accepted Answer · 2015-10-14 13:14:36Z

24

You can't. Don't do that. Use an array.

This is a version of Bash FAQ 050.

VARS=("" A B C)
for var in "${VARS[@]}"; do
    : ...
done

And you almost never want to use an unquoted variable (like for var in $VARS).

answered Oct 14, 2015 at 13:14

Etan Reisner

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Comments

123 · Accepted Answer · 2015-10-14 13:16:10Z

12

I would suggest using an array

#!/bin/bash

array=("" 1 2 "")

for i in "${array[@]}";do
    echo $i
done

answered Oct 14, 2015 at 13:16

123

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2 Comments

M K Over a year ago

Note: the quotes around "${array[@]}" are important, otherwise it won't work.

m13op22 Over a year ago

Explanation for the previous comment.

Paul · Accepted Answer · 2024-11-20 16:17:26Z

0

I was constructing an array containing another bash variable, variablea, that happened to be empty. It is important in this case to initialize such an array by quoting the bash variable.

VARS=( "$variablea" )

answered Nov 20, 2024 at 16:17

Paul

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