Bash array fails to populate if function is executed as if condition

Question

I have a function which populates a global bash array

#!/bin/bash

# Array to store debugger IDs
ID=()

fill_id()
{
    for i in 1 2 3 4 5
    do
        ID+=( $i )
    done

    echo "fill_ids      - entries in ID: ${#ID[*]}"
}

If function is called directly, array gets populated and entry count is printed as 5

fill_id
echo "main          - entries in ID: ${#ID[*]}"

Output

fill_ids      - entries in ID: 5
main          - entries in ID: 5

But if function is called in if condition then entry count is printing as 0

if (fill_id)
then
    echo "main          - entries in ID: ${#ID[*]}"
fi

Output

fill_ids      - entries in ID: 5
main          - entries in ID: 0

Return value of fill_fd is not affecting anything either.

I tried replacing array with a varible and same observation – Shubham Nov 20 '19 at 13:03 — Shubham, Nov 20 '19 at 13:03

score 4 · Accepted Answer · edited Nov 20 '19 at 13:46

you are executing function in a subshell so it changes variable of child shell which is not visible in parent shell culprit is "()" you can debug it with printing shell id - see bellow:

#!/bin/bash

# Array to store debugger IDs
ID=()

echo $BASHPID
fill_id()
{
    for i in 1 2 3 4 5
    do
        ID+=( $i )
    done
echo $BASHPID
    echo "fill_ids      - entries in ID: ${#ID[*]}"
}


if  (fill_id)
then
    echo "main          - entries in ID: ${#ID[*]}"
fi

when you call function directly (without subshell) then it properly changes your variable.

Like this:

if fill_id
then
    echo "main          - entries in ID: ${#ID[*]}"
fi

Your explanation is good. You could also add a sample of the correct call of `fill_id` in the condition. — Léa Gris, Nov 20 '19 at 13:43

score 3 · Answer 2 · answered Nov 20 '19 at 13:19

3

Just don't execute the function in a subshell.

if fill_id
then
    echo "main          - entries in ID: ${#ID[*]}"
fi

answered Nov 20 '19 at 13:19

KamilCuk

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Bash array fails to populate if function is executed as if condition

2 Answers2