ueventwait

#!/bin/bash

shopt -s extglob
SYSFS=${SYSFS:-/sys}

usage() {
  echo "Usage: ${0##*/} KEY=PATTERN..." >&2
  exit 64
}

if [[ $# -eq 0 ]]; then
  usage
fi

declare -A PATTERNS=( [ACTION]=add )
while [[ $# -gt 0 ]]; do
  if [[ $1 == +([^=])=* ]]; then
    PATTERNS[${1%%=*}]=${1#*=}
  else
    usage
  fi
  shift
done

exec < <(uevent -l 1 </dev/null)
trap "kill -PIPE $! 2>/dev/null" EXIT
read -r READY

if [[ add == ${PATTERNS[ACTION]} ]]; then
  while read -r UEVENT; do
    declare -A ENV=( [ACTION]=add )

    while IFS='=' read -r KEY VALUE; do
      if [[ -n $KEY ]]; then
        ENV[$KEY]=$VALUE
      fi
    done 2>/dev/null < "$UEVENT"

    for KEY in "${!PATTERNS[@]}"; do
      if [[ ${ENV[$KEY]} != ${PATTERNS[$KEY]} ]]; then
        continue 2
      fi
    done

    echo "${UEVENT%/uevent}"
    exit 0
  done < <(find $SYSFS/devices -name uevent -type f)
fi

declare -A ENV=()
while read -r KEY VALUE; do
  if [[ -n $KEY ]]; then
    ENV[$KEY]=$VALUE
    continue
  fi

  for KEY in "${!PATTERNS[@]}"; do
    if [[ ${ENV[$KEY]} != ${PATTERNS[$KEY]} ]]; then
      declare -A ENV=()
      continue 2
    fi
  done

  echo "$SYSFS${ENV[DEVPATH]}"
  exit 0
done

exit 1