bash哪个OR运算符使用-管道v双管道

问题描述

当我查看bash脚本代码时，有时会看到 | ，有时会看到 || ，但是我不知道哪个更合适.

When I'm looking at bash script code, I sometimes see | and sometimes see ||, but I don't know which is preferable.

我正在尝试做类似..

I'm trying to do something like ..

set -e;

ret=0 && { which ansible || ret=$?; }

if [[ ${ret} -ne 0 ]]; then
    # install ansible here
fi

在这种情况下，请告知首选哪个OR运算符.

Please advise which OR operator is preferred in this scenario.

推荐答案

| 根本不是OR运算符.不过，您可以使用 || :

| isn't an OR operator at all. You could use ||, though:

which ansible || {
  true # put your code to install ansible here
}

这等效于 if :

if ! which ansible; then
  true # put your code to install ansible here
fi

---

顺便说一句-考虑养成使用 type (内置shell)而不是 that (外部命令)的习惯. type 速度更快，并且对shell行为有更好的了解:如果您有一个 ansible 命令，例如，由调用真实命令的shell函数提供的不会知道它在那里，但是 type 会正确地将其检测为可用.

---

By the way -- consider making a habit of using type (a shell builtin) rather than which (an external command). type is both faster and has a better understanding of shell behavior: If you have an ansible command that's provided by, say, a shell function invoking the real command, which won't know that it's there, but type will correctly detect it as available.

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