Bash脚本，如果逻辑为if，则在逻辑上与ands和ors [英] Bash script with logical ands, and ors in an if elif else statement

问题描述

我已经搜索并找到了很多if elif函数的示例，但我发现似乎都没有包含逻辑AND或OR运算符。

I've searched and found a lot of examples of if elif functions, but none I have found seem to also include logical AND or OR operators.

I' m在bash脚本中遇到以下if语句时遇到问题：

I'm having trouble with the following if statement in a bash script:

#!/bin/bash

BASE="$(basename "${PWD}")"
REPO="$(cut -d/ -f4 <<<"${PWD}")"
if [ "$BASE" = "$REPO" ] -o [ "$BASE" = "" ]
then
  echo "[$REPO]"
elif [ "$REPO" = "" ] -a [ "$BASE" != "" ]
then
  echo "$BASE"
else
  echo "[$REPO] $BASE"
fi

我正在接受ol' bash：[：参数过多 IF和ELIF都出错，我似乎无法使其正常工作。 bash脚本是否不喜欢它们的IF语句来弄复杂呢？

I'm getting the ol' bash: [: too many arguments error for both the IF and the ELIF, and I can't seem to get it to work. Do bash scripts not like their IF statements to get this complex? Doesn't seem overly optimistic to expect this level of comparison, is it?

推荐答案

您正在混合<$ c的语法$ c> [ aka test 和Bash本身。在 [和] 之间， -a 是布尔值AND ，但这只是该特定命令的功能。

You are mixing the syntax of [ aka test and Bash itself. Between [ and ], -a is a boolean AND, but it is only a feature of this particular command.

在一般情况下， command1&&仅当 command1 返回成功时，command2 将执行 command2 ，类似地， command1 ||仅当 command1 返回失败时，command2 才会执行 command2 。

In the general case, command1 && command2 will execute command2 only if command1 returns success, and similarly, command1 || command2 will execute command2 only if command1 returns failure.

所以你可以说

if [ condition1 -a condition2 ]

或

if [ condition1 ] && [ condition2 ]

但是无论如何，您的代码看起来确实是您想要的 case 代替。按照您的脚本的逻辑，我遇到了一个问题，但是可以将其简化很多，因为实际上在任何情况下都不能使用 basename $ PWD 空字符串（在根目录中，基本名称为 / ）。另外，在 elif 分支中，您已经知道 $ BASE 不为空（现在忽略它的事实）永远不会为空），因为如果是的话， if 分支将已经被采用。

But anyway, your code looks like you actually want case instead. I'm having a bit of an issue following the logic of your script, but it can be simplified quite a lot, because there are actually no situations where basename $PWD can be the empty string (in the root directory, the basename is /). Also, in the elif branch, you already know that $BASE is not empty (ignoring for now the fact that it never will be empty), because if it were, the if branch would have been taken already.

假设您要检查我们是在根目录还是在下四级的目录中；或（b）在小于四级的非根目录中；否则在其他地方（c）（这意味着目录下移五个或更多级别），请尝试此操作。因为 case 将采用第一个匹配的分支（请记住， * 甚至会匹配包含斜杠的字符串）

Anyway, assuming you want to check whether we are in (a) the root directory or a directory exactly four levels down; or (b) in a non-root directory less than four levels down; or else (c) somewhere else (which means a directory five or more levels down), try this. Because case will take the first matching branch (keeping in mind that * will match even a string containing a slash in this context if necessary), I had to reorder these slightly.

case $PWD in
    /*/*/*/*/* )   # more than 4  (c)
        echo "[$REPO] $BASE" ;;
    / | /*/*/*/* )  # root or exactly 4  (a)
        echo "[$REPO"] ;;
    *)             # else, less than 4, not root  (b)
        echo "$BASE" ;;
esac

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