Various ways to resolve a script path in bash

resolve_paths.sh

#!/usr/bin/env bash
#
# For my own reference in the future demo's various ways to resolve a script's full qualified path

# Usage: copy this file to /tmp/resolve_paths_demo.sh and run it from root
#
# Note: this script uses the 'realpath' utility - to get this on OSX, you need to install 'brew install coreutils'

if [  -z "${doit+x}" ]; then # for if [exists $var] technique, see http://stackoverflow.com/a/13864829/51264
  scriptfilereal=$(realpath -P "$0")
  rm -rf /tmp/resolve_path_test >/dev/null
  mkdir -p /tmp/resolve_path_test/real/
  mkdir -p /tmp/resolve_path_test/other_real/
  mkdir -p /tmp/resolve_path_test/curdir/
  cat > /tmp/resolve_path_test/real/demo_resolve_paths.sh <<EOF
#!/usr/bin/env bash
doit=1
EOF
  chmod +x /tmp/resolve_path_test/real/demo_resolve_paths.sh
  cat $scriptfilereal >> /tmp/resolve_path_test/real/demo_resolve_paths.sh
  # symlink parent folder
  ln -s /tmp/resolve_path_test/real /tmp/resolve_path_test/linked_real
  # symlink file itself
  ln -s /tmp/resolve_path_test/real/demo_resolve_paths.sh /tmp/resolve_path_test/other_real/linked_demo_resolve_paths.sh
  pushd /tmp/resolve_path_test/curdir/  >/dev/null
  echo ""
  echo "# calling real path, real file: ../real/demo_resolve_paths.sh"
  ../real/demo_resolve_paths.sh
  echo ""
  echo "# calling symlinked path, real file: ../linked_real/demo_resolve_paths.sh"
  ../linked_real/demo_resolve_paths.sh
  echo ""
  echo "# calling other_real path, symlinked file: ../other_real/linked_demo_resolve_paths.sh"
  ../other_real/linked_demo_resolve_paths.sh
  echo ""
  popd >/dev/null
  rm -rf /tmp/resolve_path_test >/dev/null
  exit 0;
fi

scriptcmd=$0
scriptcmddir=${0%/*} # alternative to dirname, see http://stackoverflow.com/a/192524/51264
scriptfile=$(realpath -s "$0")
scriptpath=${scriptfile%/*}
scriptfilereal=$(realpath -P "$0")

echo "Script (cmd): $scriptcmd"
echo "Script (cmd path): $scriptcmddir"
echo "Script (absolute path): $scriptpath"
echo "Script (cmd absolute): $scriptfile"
echo "Script (cmd symlinks resolved): $scriptfilereal"

result.txt

# calling real path, real file: ../real/demo_resolve_paths.sh
Script (cmd): ../real/demo_resolve_paths.sh
Script (cmd path): ../real
Script (absolute path): /private/tmp/resolve_path_test/real
Script (cmd absolute): /private/tmp/resolve_path_test/real/demo_resolve_paths.sh
Script (cmd symlinks resolved): /private/tmp/resolve_path_test/real/demo_resolve_paths.sh

# calling symlinked path, real file: ../linked_real/demo_resolve_paths.sh
Script (cmd): ../linked_real/demo_resolve_paths.sh
Script (cmd path): ../linked_real
Script (absolute path): /private/tmp/resolve_path_test/linked_real
Script (cmd absolute): /private/tmp/resolve_path_test/linked_real/demo_resolve_paths.sh
Script (cmd symlinks resolved): /private/tmp/resolve_path_test/real/demo_resolve_paths.sh

# calling other_real path, symlinked file: ../other_real/linked_demo_resolve_paths.sh
Script (cmd): ../other_real/linked_demo_resolve_paths.sh
Script (cmd path): ../other_real
Script (absolute path): /private/tmp/resolve_path_test/other_real
Script (cmd absolute): /private/tmp/resolve_path_test/other_real/linked_demo_resolve_paths.sh
Script (cmd symlinks resolved): /private/tmp/resolve_path_test/real/demo_resolve_paths.sh