# from another shell script
source myScript.sh

# from command prompt, or another shell script
./myScript.sh

some_function() {
    # ...
}
if [ -z "$IS_SOURCED" ]; then
    some_function;
fi

$ cat example.sh
#!/bin/bash
script_name=$( basename ${0#-} ) #- needed if sourced no path
this_script=$( basename ${BASH_SOURCE} )
if [[ ${script_name} = ${this_script} ]] ; then
    echo "running me directly"
else
    echo "sourced from ${script_name}"
fi

$ cat example2.sh
#!/bin/bash
. ./example.sh

$ ./example.sh
running me directly
$ ./example2.sh
example.sh sourced from example2.sh

function isSourced () {
  [[ "${FUNCNAME[1]}" == "source" ]]  && return 0
  return 1
}

local _top_of_stack=$(( ${#FUNCNAME[@]} - 1 ))

function inspFnStack () {
  local T+="  "
  local _at=
  local _text="n"
  local _top=$(inspFnStackTop)
  local _fn=${FUNCNAME[1]}; [[ $_fn =~ source|main ]]  || _fn+="()"
  local i=_top; ((--i))
  #
  _text+="$i item function call stack for $_fn ...n"
  _text+="| L   BASH_SOURCE{BASH_LINENO called from}.FUNCNAME  n"
  _text+="| ---------------------------------------------------n"
  while (( $i > 0 ))
  do
    _text+="| $i ${T}$(inspFnStackItem $i)n"
    T+="  "
    ((--i))
  done
  #
  printf "$_textn"
  #
  return 0
}

function inspFnStackItem ()  {
  local _i=$1
  local _fn=${FUNCNAME[$_i]}; [[ $_fn =~ source|main ]]  || _fn+="()"
  local _at="${BASH_LINENO[$_i-1]}"; [[ $_at == 1 ]]  && _at="trap"
  local _item="${BASH_SOURCE[$_i]}{${_at}}.$_fn"
  #
  printf "%s" "$_item"
  return 0
}

function inspFnStackTop () {
  # top stack item is 1 less than length of FUNCNAME array stack
  printf "%dn" $(( ${#FUNCNAME[@]} - 1 ))
  #
  return 0
}

$ . sourced.sh
bash
$ source sourced.sh
bash
$ chmod +x sourced.sh
$ ./sourced.sh
./sourced.sh
$ cat ./sourced.sh
echo $0