bash:“哪个adb"；不返回任何内容，但返回"command -v adb"；返回我的期望 [英] bash: "which adb" returns nothing, but "command -v adb" returns what i'd expect

问题描述

这是一个让我烦恼的怪癖.

This is a bash weirdness that's been bugging me.

我在OSX上.

我已经安装了android SDK，因此adb工具位于我的主目录中的文件夹中.该文件夹显示在我的路径中，由env报告为~/Development/android_sdk_latest/platform-tools.

I've installed the android SDK, and as a result the adb tool is located in a folder in my home directory. That folder appears in my path as reported by env as ~/Development/android_sdk_latest/platform-tools.

adb本身运行正常，但是当我执行which adb时，结果为空.如果我执行command -v adb，则结果是完整路径，如预期的那样:/Users/me/Development/android_sdk_latest/platform-tools/adb

adb itself runs just fine, but when I do which adb the result is empty. If I do command -v adb, the result is the full path, as expected: /Users/me/Development/android_sdk_latest/platform-tools/adb

adb没有出现在我的别名中.

adb does not appear in my aliases.

bash路径或which有什么微妙的地方吗?

What subtlety of bash paths or which am I in the dark on?

推荐答案

您在/bin/bash和which命令之间遇到了微妙的不兼容性.

You've run into a subtle incompatibility between /bin/bash and the which command.

在我的系统(Linux Mint)上，which命令实际上是一个Shell脚本，而不是内置命令，它的第一行是#! /bin/sh.这意味着它使用/bin/sh对$PATH变量的处理.

On my system (Linux Mint), the which command is actually a shell script, not a built-in command, and its first line is #! /bin/sh. That means that it uses /bin/sh's handling of the $PATH variable.

这可能取决于/bin/sh的设置方式(有时是指向/bin/bash的符号链接)，但是一些实验表明bash处理$PATH中的文字~字符就像主目录的完整路径，但/bin/sh则没有.既然你有

This can vary depending on how /bin/sh is set up (it's sometimes a symlink to /bin/bash), but a little experimentation shows that bash handles a literal ~ character in $PATH as if it were the full path to your home directory, but /bin/sh does not. Since you have

~/Development/android_sdk_latest/platform-tools

作为$PATH的元素之一，bash(您的交互式外壳)可以找到adb命令，但是sh(由which使用的外壳)找不到.

as one of the elements of your $PATH, bash (your interactive shell) can find the adb command, but sh (the shell used by which) cannot.

在某些系统上，显然包括OSX系统，which是二进制可执行文件.同样，由于它不是bash脚本，因此不会与bash对$PATH的处理相匹配.

On some systems, apparently including your OSX system, which is a binary executable. Again, since it's not a bash script, it's not going to match bash's treatment of $PATH.

我建议进行两项更改.

首先，不要在您的$PATH中放置文字~.例如，要将platform-tools目录附加到您的$PATH，而不是此文件:

First, don't put a literal ~ in your $PATH. For example, to append the platform-tools directory to your $PATH, rather than this:

export PATH="$PATH:~/Development/android_sdk_latest/platform-tools" # BAD!

执行以下操作:

export PATH="$PATH:$HOME/Development/android_sdk_latest/platform-tools"

$HOME将扩展到主目录的路径(运行export命令时，而不是稍后使用$PATH时). ~不能在双引号字符串内扩展.

The $HOME will expand to the path to your home directory (when you run the export command, not when you use $PATH later). ~ is not expanded within double-quoted strings.

第二，而不是使用which命令，而是使用bash内置的type命令. type将遵循当前shell的规则，而不是/bin/sh的规则，并且它将能够报告which无法看到的shell函数和别名.它有几个有用的命令行选项.在bash提示符下键入help type以获得详细信息.

Second, rather than using the which command, use the type command that's built into bash. type will follow the rules of your current shell rather than those of /bin/sh, and it will be able to report shell functions and aliases that which is unable to see. It has several useful command-line options; type help type at a bash prompt for details.

bash中记录了bash外壳对$PATH中的~字符的处理.手册中关于.

The bash shell's treatement of ~ characters in $PATH is documented in the bash manual's section on Tilde Expansion.

这篇关于bash:“哪个adb"；不返回任何内容，但返回"command -v adb"；返回我的期望的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！