linux 获取当前脚本的绝对路径 | aimuke

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[linux 获取当前脚本的绝对路径](/linux/2019/04/29/how-to-get-abusolute-path/ "linux获取当前脚本的绝对路径")
====================================================================================

sr-annote { all: unset; }

一般我们写 Shell 脚本的时候，都倾向使用绝对路径，这样无论脚本在什么目录执行，都应该起到相同的效果，但是有些时候，我们设计一个软件包中的工具脚本，可能使用相对路径更加灵活一点，因为你不知道用户会在哪个目录执行你的程序，就有了本文的题目。

pwd
===

常见的一种误区，是使用 `pwd` 命令，该命令的作用是`print name of current/working directory`，这才是此命令的真实含义，当前的工作目录，这里没有任何意思说明这个目录就是脚本存放的目录。所以，这是不对的。你可以试试 bash shell/a.sh，a.sh 内容是 pwd，你会发现，显示的是执行命令的路径 /home/june，并不是 a.sh 所在路径：/home/june/shell/a.sh

$0
==

另一个误人子弟的答案，是 `$0`，这个也是不对的，这个 $0 是 Bash 环境下的特殊变量，其真实含义是：

Expands to the name of the shell or shell script. This is set at shell initialization. If bash is invoked with a file of commands, $0 is set to the name of that file. If bash is started with the -c option, then$ 0 is set to the first argument after the string to be executed, if one is present. Otherwise, it is set to the file name used to invoke bash, as given by argument zero.

这个 $0 有可能是好几种值，跟调用的方式有关系：

*   使用一个文件调用 bash，那 $0 的值，是那个文件的名字 (没说是绝对路径噢)
*   使用 - c 选项启动 bash 的话，真正执行的命令会从一个字符串中读取，字符串后面如果还有别的参数的话，使用从 $0 开始的特殊变量引用 (跟路径无关了)
*   除此以外，$0 会被设置成调用 bash 的那个文件的名字 (没说是绝对路径)

下面对比下正确答案：

```
Jun@VAIO 192.168.1.216 23:52:54 ~ >
cat shell/a.sh
#!/bin/bash
echo '$0: '$0
echo "pwd: "`pwd`
echo "============================="
echo "scriptPath1: "$(cd `dirname $0`; pwd)
echo "scriptPath2: "$(pwd)
echo "scriptPath3: "$(dirname $(readlink -f $0))
echo "scriptPath4: "$(cd $(dirname ${BASH_SOURCE:-$0});pwd)
echo -n "scriptPath5: " && dirname $(readlink -f ${BASH_SOURCE[0]})

```

```
Jun@VAIO 192.168.1.216 23:53:17 ~ > bash shell/a.sh
$0: shell/a.sh
pwd: /home/Jun
=============================
scriptPath1: /home/Jun/shell
scriptPath2: /home/Jun
scriptPath3: /home/Jun/shell
scriptPath4: /home/Jun/shell
scriptPath5: /home/Jun/shell

```

在此解释下 scriptPath1 ：

*   dirname $0，取得当前执行的脚本文件的父目录
*   cd `dirname $0`，进入这个目录 (切换当前工作目录)
*   pwd，显示当前工作目录 (cd 执行后的)

由此，我们获得了当前正在执行的脚本的存放路径。

dirname
=======

我们知道 dirname 可以获取一个文件所在的路径，dirname 的用处是：

输出已经去除了尾部的”/” 字符部分的名称；如果名称中不包含”/”， 则显示”.”(表示当前目录)。

```
[ubuntu@xxxx:~/]$ dirname --help
Usage: dirname [OPTION] NAME...
Output each NAME with its last non-slash component and trailing slashes
removed; if NAME contains no /'s, output '.' (meaning the current directory).

-z, --zero     separate output with NUL rather than newline
      --help     display this help and exit
      --version  output version information and exit

Examples:
  dirname /usr/bin/          -> "/usr"
  dirname dir1/str dir2/str  -> "dir1" followed by "dir2"
  dirname stdio.h            -> "."

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
For complete documentation, run: info coreutils 'dirname invocation'

```

从上面的描述可知道，直接从`dirname`返回的未必是绝对路径，取决于提供给`dirname`的参数是否是绝对路径。 所以下面这样的代码中 SHELL_FOLDER 中不一定是绝对路径

```
SHELL_FOLDER=$(dirname "$0")

```

需要用 cd 和 pwd 命令配合获取脚本所在绝对路径，正确的写法是这样的，

```
SHELL_FOLDER=$(cd "$(dirname "$0")";pwd)

```

readlink
========

如果你觉得上面的写法比较麻烦，还有一个方式获取脚本的绝对路径, 就是借助`readlink`命令，下面是 readlink 的命令行说明：

```
$ readlink --help
Usage: readlink [OPTION]... FILE...
Print value of a symbolic link or canonical file name

-f, --canonicalize            canonicalize by following every symlink in
                                every component of the given name recursively;
                                all but the last component must exist
  -e, --canonicalize-existing   canonicalize by following every symlink in
                                every component of the given name recursively,
                                all components must exist
  -m, --canonicalize-missing    canonicalize by following every symlink in
                                every component of the given name recursively,
                                without requirements on components existence
  -n, --no-newline              do not output the trailing delimiter
  -q, --quiet,
  -s, --silent                  suppress most error messages
  -v, --verbose                 report error messages
  -z, --zero                    separate output with NUL rather than newline
      --help     display this help and exit
      --version  output version information and exit

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
For complete documentation, run: info coreutils 'readlink invocation'

```

所以用 readlink 命令我们可以直接获取 $0 参数的全路径文件名，然后再用 dirname 获取其所在的绝对路径：

```
SHELL_FOLDER=$(dirname $(readlink -f "$0"))

```

答案
==

```
## 正确实现
# 通过 readlink 获取绝对路径，再取出目录
work_path=$(dirname $(readlink -f $0))

# 或者曲线救国
work_path=$(cd "$(dirname "$0")";pwd)

```

参考文献
====

*   [bash shell: 获取当前脚本的绝对路径 (pwd/readlink)](https://blog.csdn.net/10km/article/details/51906821)
    
*   [bash shell 获取当前正在执行脚本的绝对路径](https://my.oschina.net/leejun2005/blog/150662)
    
*   [Four ways to extract the current directory name](https://www.linux.com/news/four-ways-extract-current-directory-name)

[linux](/categories/#linux)

[linux](/tags/#linux) [shell](/tags/#shell) [pwd](/tags/#pwd) [dirname](/tags/#dirname)

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发表于 2019-04-29