问题
Why does setting a PATH require the :${PATH} at the end?
PATH="/Library/Frameworks/Python.framework/Versions/2.7/bin:${PATH}"
When I append a path to this I would do
PATH=$PATH:...
How do I append a PATH without going to a new line. That is, how would I append a PATH to the original PATH statement.
If I wanted to put the following all in the first line, for instance. How does this interact with the :${PATH} part?
PATH=$PATH:/usr/local/mysql/bin
回答1:
There's a difference between appending an existing path to the front or the end of the $PATH environment variable. The way bash resolves execution paths is by starting from the front of the list. That means if you have these two directories in your path:
PATH="/dir1/bin:/dir2/bin"
And they both have the executable test.sh in it, then when you run test.sh, it'll execute the one in /dir1/bin/test.sh since that directory appears first in the path.
Additionally, ${PATH} is the same as $PATH.
PATH="/Library/Frameworks/Python.framework/Versions/2.7/bin:${PATH}"
is simply adding /Library/Frameworks/Python.framework/Versions/2.7/bin to the front of the path and
PATH=$PATH:/usr/local/mysql/bin
is simply adding /usr/local/mysql/bin to the end of the path.
So how do you do both in one line? Something like this:
PATH="/Library/Frameworks/Python.framework/Versions/2.7/bin:${PATH}:/usr/local/mysql/bin"
来源：https://stackoverflow.com/questions/19231286/setting-path-in-bash-profile