ctags

Generates an index (or tag) file of language objects found in source files for many popular programming languages. More information: https://ctags.io/.

• Generate tags for a single file, and output them to a file named "tags" in the current directory, overwriting the file if it exists:
  ctags {{path/to/file}}
• Generate tags for all files in the current directory, and output them to a specific file, overwriting the file if it exists:
  ctags -f {{path/to/file}} *
• Generate tags for all files in the current directory and all subdirectories:
  ctags --recurse
• Generate tags for a single file, and output them with start line number and end line number in JSON format:
  ctags --fields=+ne --output-format=json {{path/to/file}}