Up until recently that I still use the very basic search function of VIM to navigate a codebase, which kind of sucks. For example, to find the class definition for SslServerStream in mono, I would do something like find . -name '*.cs' -exec grep -iRHn 'SslServerStream'. But, the problems were 1) it took a long time to search for it, 2) it gave me every match for the SslServerStream, including references, definitions, comments, although the class defintion is all I need. It was no good experience by any means.

Then, I came across ctags with vim and wished I had knew it sooner! Without it, I had wasted tons of time navigating a large code base and making myself overwhelmed.

Ctags basically goes through your code base, analyzes the code, creates tags for classes, functions, and variables and saves the tags and their location in the code base, to a tag file. The tag file then serves as the source of meta information for vim, so that you may navigate the code base easily. It is worth noting that the tag function is builtin with vim. No extra plugin is needed.

This tutorial provides a quite informative description of how to use it.

Briefly, here is how:

Create tags

To create tags for your code base: ctags -R *, -R is for ‘recursively’. This will create tags for source files of all programming languages under current folder recursively. You will find ctags creates a file named tags under the current directory. Ctag also allows to specify languages by --languages option followed by a comma delimited list. To generate tags for Java and C++ source file for example, say ctags -R * --laguages:Java,C++

Use tags

There are two ways to use tags.

1. From your shell, say vim -t tag_name. This will get you directly to the first tag associated with the specified tag_name. For instance, if you say vim -t Stop, vim will open a source file with the cursor placed on the definition of the tag Stop, which can be a class, function, or a variable.

2. If you are already inside VIM, here are the relevant commands you may use to play with the tags.

Commands	Function
Control+]	Go the definition of the tag the cursor points to
:ts mytag	Search and list for mytag
:tn	Go to the nexttag definition
:tp	Go to the previous tag definition
:ts	List definitions for the last tag
Control+t	Get to the last tag in the tag stack

A little more on the last command. Say you are trying to make sense of a class A. Sometimes you have to take a detour to understand the B which is referenced in the defintion of A. So you do Control+] on B and read the code of B, and then you want to get back to where you initiated the search for B because you want to end the detour and continue on A. Control+t will do the trick for you.

That’s it. Have fun VIMming!