使用var = $?测试命令的存储退出状态； [[$ var]]始终为true，无论是0还是1 [英] Testing a command's stored exit status with var=$?; [[ $var ]] is always true, whether 0 or 1

问题描述

考虑:

true; run_backup=$?
if [[ $run_backup ]]; then
  echo "The user wants to run the backup"
fi

...和...

false; run_backup=$?
if [[ $run_backup ]]; then
  echo "The user wants to run the backup"
fi

不管run_backup具有0(成功)还是1(假)，都会发出

The user wants to run the backup！

The user wants to run the backup is emitted whether run_backup has 0 (success) or 1 (false)!

这是怎么回事?

(我的真实命令而不是true或false的形式为zenity --question --text "...").

(My real command, instead of true or false, is of the form zenity --question --text "...").

推荐答案

[[ $run_backup ]]不是布尔值检查；仅当其参数为空字符串(0和1都不为空)时，它才会失败.

[[ $run_backup ]] is not a Boolean check; it fails only if its argument is an empty string (which neither 0 nor 1 is).

由于zenity如果单击确定"，则返回0，因此您需要类似

Since zenity returns 0 if you click OK, you want something like

[[ $run_backup -eq 0 ]] && echo "The user wants to run the backup"

或

(( run_backup == 0 )) && echo "The user wants to run the backup"

或

# You need to negate the value because success(0)/failure(!=0) use
# the opposite convention of true(1)/false(0)
(( ! run_backup )) && echo "The user wants to run the backup"

---

基于原始问题中run_backup是zenity命令的退出状态这一事实，最简单的事情就是简单地使用&&将zenity和您的函数组合为一个命令./p>

---

Based on the fact that run_backup was the exit status of a zenity command in the original question, the simplest thing would be to simply use && to combine zenity and your function into one command.

zenity --question --width=300 --text "..." && echo "The user wants to run the backup"

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