How to properly parse a quoted arg-list string in a shell script?

Question

Summary

How to convert a single string a "b" 'c d' $'e\nf' into separate arguments, respecting quotes and preserving whitespaces and newlines?

Question

I'm trying to read and process the output of a script that exports value lists, one per line, in form of quoted strings (as created by printf %q). The values within a list are space-separated, may be quoted, may include spaces and newlines, and are of unknown count.

Example: a "b" 'c d' $'e\nf'

I'm looking for a way to restore the values in a POSIX shell script and handle them as arguments to a shell function.

Desired solutions, in descending priority:

1. POSIX shell commands and core utilities like xargs, printf and the like; no eval
2. Bash
3. A full-blown programming language like perl

Skeleton for the shell script process.sh:

#!/bin/sh
set -eu

process() {
  printf '>%s<\n' "${@}"
}

main() {
  value_list="${1}"
  # split value list here and set positional parameters
  set -- ???
  process "${@}"
}

main "${@}"

Desired behaviour

$ process.sh "a \"b\" 'c d' $'e\nf'"
>a<
>b<
>c d<
>e
f<

What happened so far

• I tried different combinations of printf (incl. %q), xargs, while read loops, changing IFS, separation of args with a null byte, subshell invocations, heredocs.
• xargs allows unquoting, but only for spaces, not for newlines, and only without argument -d.
• A while read loop can parse args, but does not allow to call a shell function when input is read from a pipe

Answer 1

This answer is based on a comment by ilkkachu and uses zsh.

Shell script process.sh:

#!/bin/sh
set -eu
export script="$(readlink -f "${0}")"

split() {
  zsh -c 'printf "%s\0" "${(Q@)${(z)1}}"' "${script}/split" "${@}"
}

process() {
  printf '>%s<\n' "${@}"
}

main() {
  value_list="${1}"
  split "${value_list}" | xargs -0 sh -c 'init() { . "${script}"; } && init && process "${@}"' "${script}/main"
}

[ "${#}" -eq 0 ] || main "${@}"

Benefits

• It works

Drawbacks

• Script must be sourced to call process() form xargs, a little awkward wrapped in a function to strip the arguments and prevent an endless loop
• Requirement for zsh

Answer 2

A simplified variant of this zsh-based answer:

#!/bin/zsh
set -eu

process() {
  printf '>%s<\n' "${@}"
}

main() {
  value_list="${1}"
  process "${(Q@)${(z)value_list}}"
}

main "${@}"

Benefits

• It works

Drawbacks

• Requirement for zsh