Modifying $PATH variable by a bash alias - bash

Question

I created this alias in my .bashrc file:
alias changepath="export PATH=$JAVA_HOME/bin:$PATH"
What I want to do is change $JAVA_HOME and then change the $PATH to include the new $JAVA_HOME/bin.
When I change $JAVA_HOME and type this command instead of using the alias, it works as expected.
However, when I change $JAVA_HOME and then use the alias, the changepath command prepends the old $JAVA_HOME/bin instead of the new $JAVA_HOME/bin to $PATH.
How can I fix this?

Answer 1

You can also defer evaluation of variables by single-quoting your alias definition, i.e.
alias changepath='export PATH=$JAVA_HOME/bin:$PATH'
Note that the alias or function solutions do not solve the problem of clearing any previous JAVA_HOME you have set.
So you can wind up with a crazy PATH
PATH="/usr/bin:/sys"
PATH=/usr/bin/java:/usr/bin:/sys
PATH=/usr/bin/java/bin:/usr/bin/java:/usr/bin:/sys

Answer 2

Try to use a function instead:
changepath () {
export PATH="$JAVA_HOME/bin:$PATH";
}
In your case "$JAVA_HOME and $PATH are interpreted when you set the alias. So they are fixed to the moment when you execute the .bashrc.
With a function, variables will be interpreted at launching.
Note: I copy/paste you export PATH=..., but be careful you will add $PATH's content at every launch.

Answer 3

This is how I approached the problem of changing between Java 7 and 8 SDKs. I am sure someone could improve these bash functions but I guess the important part is using sed to edit the path.
This will find and replace the JAVA_HOME value rather than keep adding to the PATH variable.
function java7 () {
export PATH=$(echo $PATH | sed s~$JAVA_HOME~${JAVA_7_HOME}"/bin"~)
export JAVA_HOME="${JAVA_7_HOME}";
}
function java8 () {
export PATH=$(echo $PATH | sed s~$JAVA_HOME~${JAVA_8_HOME}"/bin"~)
export JAVA_HOME="${JAVA_8_HOME}";
}

Answer 4

I need to switch between 8 and 11 so what I did was:
Add NO_JAVA_PATH in .profile
export NO_JAVA_PATH=$PATH
export JAVA_HOME="<path>"
export PATH=$JAVA_HOME/bin:$PATH
Added aliases in .bashrc
alias j8='export JAVA_HOME="<path>" ; export PATH=$JAVA_HOME/bin:$NO_JAVA_PATH'
alias j11='export JAVA_HOME="<path>" ; export PATH=$JAVA_HOME/bin:$NO_JAVA_PATH'