bash variable whose value changes dynamically?

Question

I'm a bash newb; just curious if this is possible...

assume i have ~/.bash_profile (mac terminal) w/ following declarations:

export src=~/Developer/src
export myapp=$src/myapp

alias buildapp='build $myapp' # just an example...

this gets loaded when i start up the terminal, and everything's fine.

what i want to do is, later when i switch to a different branch/depot/whatever, i want to type,

export src=~/Developer/temp_src

in the shell, and make $myapp automatically reference the new $src variable...

is this actually possible?

The simple answer is that this isn't possible with variables. They don't remember the expression used to assign them, and can't re-evaluate it dynamically. — Barmar
– Barmar, Commented Jun 2, 2016 at 21:59

anubhava · Accepted Answer · 2016-06-02 21:47:30Z

2

Don't create myapp variable and just use this alias:

alias buildapp='build "$src/myapp"'

Having said that, it is usually better to use a function instead of alias:

buildapp() { build "$src/myapp"; }

answered Jun 2, 2016 at 21:47

anubhava

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2 Comments

jason na Over a year ago

i thought of that, but hoped to avoid it because... i have 4-5 different variables all depending on $src, and each of them is fairly long (20-30 chars; e.g. $src/foo/bar/baz/whararara/....); and then i have bunch of aliases that reference any of those 4-5...

anubhava Over a year ago

If possible, you can put all variable assignments based on $src inside this function.

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