ctags

ctags is a program that generates an index file, often called a tags file, which describes the locations of language objects such as functions, variables, and classes found in a collection of source files. This index file can then be used by text editors to quickly locate and navigate to these definitions. ctags supports a wide variety of programming languages, making it a versatile tool for software development.

The primary function of ctags is to scan source code and identify specific language constructs. For each identified construct, it records its name, the file it resides in, and its line number or byte offset within that file. This information is stored in a plain text file, which is typically named 'tags'. Many popular text editors, including Vim, Emacs, and VS Code (with extensions), can read and utilize these tags files.

When a developer wants to jump to the definition of a function or variable, they can invoke a command within their editor, often by placing the cursor on the symbol and pressing a key combination. The editor then consults the tags file to find the precise location of the definition and instantly navigates the user to it. This significantly speeds up the process of understanding and modifying codebases, especially large or unfamiliar ones. ctags is usually invoked from the command line, specifying the files or directories to be indexed.