為什麼在這種特定情況下我不必引用字元串變數？

我的基於 Ubuntu/Debian 的 Linux 更新 POSIX shell 腳本似乎要求我不要用正在執行的儲存命令對字元串變數**進行雙引號。**由於我不明白這個問題，我想問這是為什麼？如果程式碼是正確的呢？

警告：SC2086，wiki，“雙引號以防止萬用字元和分詞。”

腳本如下，有問題的部分突出顯示：

#!/bin/sh

# exit script when it tries to use undeclared variables
set -u

# color definitions
readonly red=$(tput bold)$(tput setaf 1)
readonly green=$(tput bold)$(tput setaf 2)
readonly yellow=$(tput bold)$(tput setaf 3)
readonly white=$(tput bold)$(tput setaf 7)
readonly color_reset=$(tput sgr0)
# to create blocks of texts, I separate them with this line
readonly block_separator='----------------------------------------'

step_number=0
execute_jobs ()
{
   while [ ${#} -gt 1 ]
   do
       job_description=${1}
       job_command=${2}

       step_number=$(( step_number + 1 ))

       printf '%s\n' "Step #${step_number}: ${green}${job_description}${color_reset}"

       printf '%s\n' "Command: ${yellow}${job_command}${color_reset}"

       printf '%s\n' "${white}${block_separator}${color_reset}"

       # RUN THE ACTUAL COMMAND
       # ShellCheck warns me I should double quote the parameter
       # If I did, it would become a string (I think) and I'd get 'command not found' (proven)
       # As I don't understand the issue, I left it as I wrote it, without quotes
       ### shellcheck disable=SC2086

**``` if sudo ${job_command} # <– HERE

   then
       printf '\n'
   else
       printf '%s\n\n' "${red}An error occurred.${color_reset}"
       exit 1
   fi

   shift 2

done }

execute_jobs
‘configure packages’ ‘dpkg –configure –pending’
‘fix broken dependencies’ ‘apt-get –assume-yes –fix-broken install’
‘update cache’ ‘apt-get update’
‘upgrade packages’ ‘apt-get –assume-yes upgrade’
‘upgrade packages with possible removals’ ‘apt-get –assume-yes dist-upgrade’
‘remove unused packages’ ‘apt-get –assume-yes –purge autoremove’
‘clean up old packages’ ‘apt-get autoclean’

**你不能在這裡引用變數：

if sudo ${job_command}

因為你確實想要分詞。如果您引用，則命令變為（對於您的第一步）

if sudo "dpkg --configure --pending"

並sudo查找 command dpkg --configure --pending，而不是dpkg帶有參數的 command--configure和--pending，如其錯誤消息所示：

sudo: dpkg --configure --pending: command not found

（嘗試使用額外的空格使其更明確）。

省略引號後，shell 會拆分參數，一切都按預期工作。**

引用自：https://unix.stackexchange.com/questions/518179