shell 当前工作目录的绝对路径

#!/bin/bash

work_path=$(dirname $0)
cd ~/${work_path}
## blblbl
cd /home/lcd/
cp ./something ${work_path}

bash /home/lcd/shell/mytest.sh
# work_path -> home/lcd/shell
# 能得到想要的

lcd:/home/lcd/shell/ $ bash ./mytest.sh
# work_path -> ./
# 所以上面的执行方式，something 还是复制到了./
# 也就是最后 cd 进去的目录下

$ bash ./mytest.sh              # $0= ./mytest.sh
$ bash ./shell/mytest.sh            # $0= ./shell/mytest.sh
$ bash /home/lcd/shell/mytest.sh    # $0= /home/lcd/shell/mytest.sh

lcd:/home/lcd/shell/ $ bash ./mytest.sh 
# pwd=/home/lcd/shell/
lcd:/home/lcd/ $ bash ./shell/mytest.sh
# pwd=/home/lcd/
lcd:/root/ $bash /home/lcd/shell/mytest.sh
# pwd=/root/

# 在某些情况下会拿到错误结果
work_path=$(dirname $0)
work_path=$(pwd)

## 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=$(dirname $0)
cd ./${work_path}  # 当前位置跳到脚本位置
work_path=$(pwd)   # 取到脚本目录