Anonymous functions in shell scripts

Question

Is it possible to create something analogous to an anonymous function whose value can be assigned to an array element and later called? I can't seem to find a way to do this in a bash script but perhaps there's a workaround.

Answer 1

Short answer: No.

Long answer: Nooooooooooooo.

Complete answer: Functions in bash are not first-class objects, therefore there can be no such thing as an anonymous function in bash.

Answer 2

It is possible; I wrote a library to do exactly this, though it's a very strange project. The source code is available at http://github.com/spencertipping/bash-lambda. Using this library:

$ my_array=() $ my_array[0]=$(fn x 'echo $((x + 1))') $ my_array[1]=$(fn x 'echo $((x + 2))') $ ${my_array[0]} 5 6 $ ${my_array[1]} 5 7 $ 

The trick is to have the fn function create a file containing the body of the function, chmod +x that file, then return its name. This causes stray files to accumulate, which is why the library also implements an asynchronous mark/sweep garbage collector.