is the zsh script being sourced?

00.README.md

is the zsh script being sourced?

a traditional way

[[ $_ = $0 ]] && {
  echo 'the script is being sourced.'
  return 0
} 

It works.

❯ source traditional-way.zsh
the script is being sourced.
❯ ./traditional-way.zsh
probably, it was running as a subshell.

However, this way is broken easily as follows.

:
[[ $_ = $0 ]] && {
  echo 'the script is being sourced.'
  return 0
}

if [[ $_ = $0 ]]; then
  echo 'the script is being sourced.'
  return 0
fi

❯ source traditional-way-wrong-1.zsh 
probably, it was running as a subshell.
❯ source traditional-way-wrong-2.zsh 
probably, it was running as a subshell.

a more effective way on zsh

if [[ ${#funcstack[@]} -ne 0 ]]; then
  echo 'the script is being sourced.'
  return 0
fi

❯ source effective-way.zsh
the script is being sourced.
❯ ./effective-way.zsh
certainly, it was running as a subshell.

Links

• http://zsh.sourceforge.net/Doc/Release/Zsh-Modules.html#index-funcstack
• http://zsh.sourceforge.net/Doc/Release/Parameters.html#index-_005f

10.console.md

❯ zsh --version
zsh 5.8 (x86_64-pc-linux-gnu)

run as a subshell

❯ ./funcstack.zsh
#funcstack: 0
funcstack: 

❯ sh funcstack.zsh
#funcstack: 0
funcstack: 

❯ zsh -ic ./funcstack.zsh
#funcstack: 0
funcstack: 

sourced

❯ source funcstack.zsh  
#funcstack: 1
funcstack: funcstack.zsh

❯ zsh -ic 'source funcstack.zsh' 
#funcstack: 1
funcstack: funcstack.zsh

effective-way.zsh

#!/usr/bin/env -S zsh -eux

:

if [[ ${#funcstack[@]} -ne 0 ]]; then
  echo 'the script is being sourced.'
  return 0
fi

echo 'certainly, it was running as a subshell.'

funcstack.zsh

#!/usr/bin/env -S zsh -eu
echo "#funcstack: ${#funcstack[@]}"
echo "funcstack: ${funcstack[@]}"

traditional-way-wrong-1.zsh

#!/usr/bin/env -S zsh -eux

:

[[ $_ = $0 ]] && {
  echo 'the script is being sourced.'
  return 0
}

echo 'probably, it was running as a subshell.'

traditional-way-wrong-2.zsh

#!/usr/bin/env -S zsh -eux

if [[ $_ = $0 ]]; then
  echo 'the script is being sourced.'
  return 0
fi

echo 'probably, it was running as a subshell.'

traditional-way.zsh

#!/usr/bin/env -S zsh -eux

[[ $_ = $0 ]] && {
  echo 'the script is being sourced.'
  return 0
}

echo 'probably, it was running as a subshell.'