Linux Shell下获取当前脚本的绝对路径

时间：2022-07-06 18:47:50

错误的做法

使用pwd

一种很常见的错误做法是使用pwd命令，这个命令的作用是“print name of current/working directory”，因此当脚本执行过程中改变了工作目录，这个pwd命令返回的结果也将随之改变。

NAME
pwd - print name of current/working directory

SYNOPSIS
pwd [OPTION]…

DESCRIPTION
Print the full filename of the current working directory.

-L, –logical
use PWD from environment, even if it contains symlinks

-P, –physical
avoid all symlinks

–help
display this help and exit

–version
output version information and exit

NOTE: your shell may have its own version of pwd, which usually supersedes the version described here. Please refer to your shell’s documentation for details about the options it supports.

但无论如何，谁也无法保证当前工作目录就是脚本存放的目录。正如这样：

[chen@bwvps1 ~]$ cat ./dir1/dir2/using_pwd.sh
#!/usr/bin/env bash

echo 'pwd: ' $(pwd)

[chen@bwvps1 ~]$ using_pwd.sh
pwd:  /home/chen

[chen@bwvps1 ~]$ ./dir1/dir2/using_pwd.sh
pwd:  /home/chen

[chen@bwvps1 ~]$ . ./dir1/dir2/using_pwd.sh
pwd:  /home/chen

使用$0

另一个常见的误区是使用$0，从man bash中可以读到关于它的解释：

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.

我们来举例说明一下通常情况下它的返回值，如你所见这个$0要比pwd复杂得多：

[chen@bwvps1 ~]$ cat ./dir1/dir2/using_dzero.sh 
#!/usr/bin/env bash

echo '$0: ' $0

[chen@bwvps1 ~]$ using_dzero.sh 
$0:  /home/chen/dir1/dir2/using_dzero.sh

[chen@bwvps1 ~]$ ./dir1/dir2/using_dzero.sh 
$0:  ./dir1/dir2/using_dzero.sh

[chen@bwvps1 ~]$ . ./dir1/dir2/using_dzero.sh 
$0:  -bash

如此说来，只有dot execute或是说source执行脚本时（上例中第三种执行方式），$0不能返回脚本所在的路径，其他情况下得到的只是绝对路径和相对路径的分别，因此配合dirname $0就可以解决大多数问题。

改进的建议

当然，相对于每次纠结绝对路径还是相对路径来说，我们有一个更好的办法，可以直接获取到脚本的绝对路径。于是我们对上面的方法进行了改进，将获取方式改为$(cd $(dirname $0); pwd)。最终的结果如我们所见：

[chen@bwvps1 ~]$ cat dir1/dir2/test.sh
#!/usr/bin/env bash

echo 'pwd: ' $(pwd)
echo '$0: ' $0

BASENAME=$(cd $(dirname $0); pwd)
echo "\$BASENAME: " $BASENAME

[chen@bwvps1 ~]$ test.sh
pwd:  /home/chen
$0:   /home/chen/dir1/dir2/test.sh
$BASENAME:  /home/chen/dir1/dir2

[chen@bwvps1 ~]$ ./dir1/dir2/test.sh
pwd:  /home/chen
$0:   ./dir1/dir2/test.sh
$BASENAME:  /home/chen/dir1/dir2

[chen@bwvps1 ~]$ . ./dir1/dir2/test.sh
pwd:  /home/chen
$0:   -bash
dirname: invalid option -- 'b'
Try 'dirname --help' for more information.
$BASENAME:  /home/chen

参考文献：
1. http://www.cnblogs.com/FlyFive/p/3640267.html

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