Wordsplitting occurring in quoted variable

Question

I'm trying to create a dialog menu based on the results of the lsblk command. My goal is to read the first word as the menu item and the remaining words as the menu item description.

For example:

$ dialog --menu "Choose one:" 0 0 0 $(lsblk -lno name,size | grep sda)

This command works, because the dialog --menu option expects two arguments per menu item, in this case "name" and "size".

However, if I try the same command with a multi-word description (using the "read" built-in to write to stdout as two variables), word-splitting occurs in the second variable, even if quoted.

#commmand 1: unquoted variable
$ dialog --menu "Choose one:" 0 0 0 $(lsblk -lno name,type,size | grep sda |
> while read name desc; do
> echo $name $desc
> done)                      #results in output like below without quotes

#command 2: quoted variable 
$ dialog --menu "Choose one:" 0 0 0 $(lsblk -lno name,type,size | grep sda |
> while read name desc; do
> echo $name "$desc"
> done)                      #results in output like below without quotes

#command 3: escape quoted variable
$ dialog --menu "Choose one:" 0 0 0 $(lsblk -lno name,type,size | grep sda |
> while read name desc; do
> echo $name \"$desc\"
> done)                      #results in output below

I don't understand why word splitting is occurring in the quoted variable. Can anyone explain and/or suggest a workaround? I've tried writing the output of lsblk to a file and reading the file with the same results. The desired output is:

EDIT: I looked at command quoting as a possible solution, but it results in the lsblk command output being passed to dialog as one argument when two are required.

Thanks.

Answer 1

You need to do this in 2 parts:

# 1. read the output of lsblk, 2 words per line, into an array
parts=()
while read -r disk data; do 
    parts+=("$disk" "$data")
done < <(lsblk -lno name,type,size | grep sda)

# 2. send the elements of the array to the dialog command
dialog --menu "Choose one:" 0 0 0 "${parts[@]}"

The read command will take the first whitespace-separated work into the disk variable, and then the rest of the line into data. It's very important to quote all the variables to avoid word splitting