Pass command arguments as a variable

Rever_2019

5/11/23, 11:31 AM

I have made a bash script to back up my AWS Ligthsail server with restic. Everything works finally, but there is one thing I couldn't find an answer.

Just the part where the problem is:

//Settings
forget_policy=(--keep-within-daily 7d --keep-within-weekly 1m --keep-within-monthly 1y --keep-within-yearly 2y)

//(… other code)

forget_old () {
    # Forget and prune
    restic -r $RESTIC_REPOSITORY forget "${forget_policy}" --prune | log

    # Check if exit status is ok
    status=$?
    if [ $status -ne 0 ]; then
        log "Forget failed ${status}"
        exit 1
    fi
}

//(… other code)

forget_old

Output

>> invalid argument "--prune" for "--keep-within-daily" flag: no number found

I can't pass the $forget_policy variable to the forget command. When I wrap the varibale in "" I get

>> unknown flag: --keep-within-daily 7d --keep-within-weekly 1m --keep-within-monthly 1y --keep-within-yearly 2y

When I copy the variable content directly to the command, it works. So I must be doing something wrong with passing the variable.

0 + 0

bash

scripts

Score:1

Ubuntu

steeldriver

5/11/23, 1:16 PM

To expand each of the elements of your argument array as a separate word you need "${forget_policy[@]}"

"${forget_policy}" is equivalent to "${forget_policy[0]}" so only expands to the first argument - which is why you end up with --keep-within-daily --prune

See the Arrays subsection under PARAMETERS in the bash manual page.

0 + 0

Rever_2019

5/13/23, 2:40 PM

Thanks. I do (sadly) not enough bash scripting. Didn't notice I turned it to an array, adding the (). Before, I had just "forget_policy="--keep-within-daily 7d --…". That's just a string and didn't work. Had googeled and found the "array version"

steeldriver

5/13/23, 2:55 PM

@Rever_2019 in that case it was a happy accident - using an array is exactly the right way to handle this kind of argument list ;)

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Pass command arguments as a variable

TH: ส่งผ่านอาร์กิวเมนต์คำสั่งเป็นตัวแปร

RO: Treceți argumentele comenzii ca variabilă

RU: Передать аргументы команды как переменную

VI: Truyền đối số lệnh dưới dạng biến

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