29.5 Finding Syntax Errors On The Fly

Flymake mode is a minor mode that performs on-the-fly syntax checking for many programming and markup languages, including C, C++, Perl, HTML, and TeX/LaTeX. It is somewhat analogous to Flyspell mode, which performs spell checking for ordinary human languages in a similar fashion (see Checking and Correcting Spelling). As you edit a file, Flymake mode runs an appropriate syntax checking tool in the background, using a temporary copy of the buffer. It then parses the error and warning messages, and highlights the erroneous lines in the buffer. The syntax checking tool used depends on the language; for example, for C/C++ files this is usually the C compiler. Flymake can also use build tools such as make for checking complicated projects.

To enable Flymake mode, type M-x flymake-mode. You can jump to the errors that it finds by using M-x flymake-goto-next-error and M-x flymake-goto-prev-error. To display a detailed overview of the diagnostics for the current buffer, use the command M-x flymake-show-buffer-diagnostics; to display a similar overview of diagnostics for the entire project (see Working with Projects), use M-x flymake-show-project-diagnostics.

For more details about using Flymake, see Flymake in The Flymake Manual.