#!/bin/bash
# Bash
PROGNAME=$(basename $0)
ren() {
  local newname
  newname=${1//-/_}
  [ "$1" != "$newname" ] && mv -- "$1" "$newname"
}
traverse() {
  local i
  cd -- "$1" || exit 1
  for i in *; do
    [ -d "$i" ] && traverse "$i"
    ren "$i"
  done
  cd .. || exit 1
}
function usage
{
	echo -e "Usage: ${PROGNAME} </path/to/dir>"
}
# main program
if [ $# -ne 1 ]; then
	usage
	exit 1
else
	shopt -s nullglob
	traverse 
fi

exit $?