Example of a function that accepts input from stdin or as arguments

bash_input.sh

function trim {
  if [ $# -eq 0 ]
  then
    data=$(cat)
  else
    data="$*"
  fi

  data="${data#"${data%%[![:space:]]*}"}"
  data="${data%"${data##*[![:space:]]}"}"

  echo -n "$data"
}

#	  $ function trim {
#	  >   if [ $# -eq 0 ]
#	  >   then
#	  >     data=$(cat)
#	  >   else
#	  >     data="$*"
#	  >   fi
#	  >
#	  >   data="${data#"${data%%[![:space:]]*}"}"
#	  >   data="${data%"${data##*[![:space:]]}"}"
#	  >
#	  >   echo "$data"
#	  > }
#	  $ trim "   Hello  World    "
#	  Hello  World
#	  $ echo "   Hello  World    " | trim
#	  Hello  World