Bash: call function from "bash -c"

Question

I'm trying to get my bash function to call another function that uses bash -c. How do we make functions created earlier in the script persist between different bash sessions?

Current script:

#!/bin/bash

inner_function () {
    echo "$1"
    }
outer_function () {
    bash -c "echo one; inner_function 'two'"
    }
outer_function

Current output:

$ /tmp/test.sh 
one
bash: inner_function: command not found

Desired output:

one

two

Answer 1

Export it:

typeset -xf inner_function

Example:

#! /bin/bash
inner_function () { echo "$1"; }
outer_function () { bash -c "echo one; inner_function 'two'"; }
typeset -xf inner_function
outer_function

Other ways to write the exact same thing are export -f inner_function or declare -fx inner_function.

Notice that exported shell functions are a) a bash-only feature, not supported in other shells and b) still controversial, even after most of the bugs were fixed since shellshock.

Answer 2

When I need the same function in several scripts, I put it in a side "library" script file and "source" that (source the_lib_script or . the_lib_script) in the scripts that need the function.