exportscope

#!/usr/bin/env bash

{ code=$(</dev/fd/0); } <<\EOF
${ZSH_VERSION+false} || emulate ksh

# eval showEnv (funcname) to display the state of "x" from a subprocess.
showEnv=$'bash -c \'${x+:} typeset x=unset; printf "subprocess %s: %s\\n" "$1" "$(typeset -p x)"\' --'

function printTest {
	printf '%s test %d:\n' "$1" $((testnum++)) >&2
}

function f {
	# For ksh93 use a nameref in the one case where "x" is local to "g".
	[[ ${!KSH_VERSION} == .sh.version && -n $1 ]] && typeset -n x=$1
	typeset x='in f'
	eval "$showEnv" f
	printf 'local f: %s\n' "$(typeset -p x)"
}

# Test local export
function g {
	typeset -x x='in g'
	eval "$showEnv" g
	f x
	printf 'local g: %s\n' "$(typeset -p x)"
}

# Test nameref export
function h {
	case ${1:-1} in
		1)
			typeset x='in h1'
			h 2 x
			eval "$showEnv" h1
			printf 'local h1: %s\n' "$(typeset -p x)"
			;;
		2)
			typeset -n _x=$2
			typeset -x _x='in h2'
			eval "$showEnv" h2
	esac
}

testnum=1
printTest "$1"

# Export from global scope then test from local scope.
{
	typeset -x x=global
	f
	${x+:} typeset x=unset
	printf 'global: %s\n' "$(typeset -p x)"
} | sed 's/^/    /' # indent test output for clarity.

printTest "$1"

# Export from local scope then test from a child scope.
{
	g
	${x+:} typeset x=unset
	printf 'global: %s\n' "$(typeset -p x)"
} | sed 's/^/    /'

printTest "$1"

# Test exporting variables by reference. (Should this even work?)
{
	${ZSH_VERSION+false} || exit 0
	h 1
} | sed 's/^/    /'
EOF

for sh in bash ksh mksh zsh; do
	printf '%s\n\n' "$("$sh" -c "$code" -- "$sh" 2>&1)"
done

# vim: set fenc=utf-8 ff=unix ft=sh :

output

bash test 1:
    subprocess f: declare -x x="in f"
    local f: declare -x x="in f"
    global: declare -x x="global"
bash test 2:
    subprocess g: declare -x x="in g"
    subprocess f: declare -x x="in f"
    local f: declare -x x="in f"
    local g: declare -x x="in g"
    global: declare -- x="unset"
bash test 3:
    subprocess h2: declare -- x="unset"
    subprocess h1: declare -- x="unset"
    local h1: declare -- x="in h1"

ksh test 1:
    subprocess f: declare -- x="unset"
    local f: x='in f'
    global: typeset -x x=global
ksh test 2:
    subprocess g: declare -x x="in g"
    subprocess f: declare -- x="unset"
    local f: typeset -n x=x
    local g: x='in f'
    global: x=unset
ksh test 3:
    subprocess h2: declare -- x="unset"
    subprocess h1: declare -x x="in h2"
    local h1: typeset -x x='in h2'

mksh test 1:
    subprocess f: declare -x x="global"
    local f: typeset x='in f'
    global: typeset -x x=global
mksh test 2:
    subprocess g: declare -x x="in g"
    subprocess f: declare -x x="in g"
    local f: typeset x='in f'
    local g: typeset -x x='in g'
    global: typeset x=unset
mksh test 3:
    subprocess h2: declare -x x="in h2"
    subprocess h1: declare -- x="unset"
    local h1: typeset x='in h1'

zsh test 1:
    subprocess f: declare -- x="unset"
    local f: typeset x='in f'
    global: typeset -x x=global
zsh test 2:
    subprocess g: declare -x x="in g"
    subprocess f: declare -- x="unset"
    local f: typeset x='in f'
    local g: typeset -x x='in g'
    global: typeset x=unset
zsh test 3: