Higher order functions in bash

[jerith]

I recently had occasion to refactor a bunch of bash scripts, and one of the problems was that certain loop constructs were cropping up a lot. A quick search didn't turn up a way to do higher order functions in bash, so I (re)invented one:

higher_order() {
# some code
eval "$1"
# some more code
}The eval evaluates the code passed as a

Comments

[msmercenary]

I started doing this in mIRC about four years ago, and my scripts became an order of magnitude cooler overnight. Schlockbot and servernotices make a lot of use of this type of metafunctionality.

Of course, all my mIRC script messing around culminated in the PiBot, so there's clearly risk involved.

[jerith]

Updated with pointer to a more complete version on my website.

I wouldn't use most of this stuff in anger, though. By the time it's necessary, I've usually switched to a different language. The only reason I did it in this case was that I was writing system build scripts and I can't assume that anything other than the most basic tools are available.

Why eval?

[anonymous]

Why use eval at all?

You could simply do:

$ FOO="hello world"
$ $FOO
$ $FOO

No?

Alejo, from http://azul.freaks-unidos.net/

Re: Why eval?

[jerith]

Partly because it makes what I'm doing a little more explicit and partly because I didn't thing of the other way until I'd already written the code.