Ways of checking if a file is "a symlink" and is "broken".

symlink-checker-tests.bash

#!/bin/sh

set -eu

tempdir=''

setup() {
  tempdir="$(mktemp -d)"
  cd "$tempdir"

  touch target
  ln -nsf target good
  ln -nsf nosuch bad
  ln -nsf good goodgood
  ln -nsf bad badgood
}

teardown() {
  if [ -d "$tempdir" ]; then
    rm -rf "$tempdir"
  fi
}

check() {
  printf "%s is " "${1}"
  eval "tput bold; if ${1}; then tput setaf 6; echo true; else tput setaf 1; echo false; fi; tput sgr0"
}

run() {
  echo POSIX
  for f in *; do
    check "[ -h $f ]"
    check "[ -L $f ]"
    check "[ -e $f ]"
    check "[ -f $f ]"
  done
  echo NON-POSIX
  for f in *; do
    check "[[ -h $f ]]"
    check "[[ -L $f ]]"
    check "[[ -a $f ]]"
    check "[[ -e $f ]]"
    check "[[ -f $f ]]"
  done
  echo OTHER TOOLS
  for f in *; do
    # check "find $f -type l \! -exec test -e {} \; -print"
    check "[ -z \"\$(find -L $f -type l)\" ]"
    check "[ -z \"\$(gfind -L $f -type l)\" ]"
  done
}

## Main ##

setup
trap teardown EXIT
run

## EOF ##