makefile

A Makefile is a special file used by the make utility to control the building of programs and other tasks. It describes how to derive target files from a set of prerequisite files and commands, allowing incremental builds and automation.

A rule in a Makefile has the form target: prerequisites and a recipe. The recipe is a sequence of shell commands executed to create the target from the prerequisites. Variables can be defined and referenced as $(VAR). Common targets include programs, libraries, and auxiliary tasks.

Makefiles support features such as include directives to pull in other files, pattern rules using the % wildcard, and automatic variables such as $@ for the target name, $< for the first prerequisite, and $^ for all prerequisites. Special targets like .PHONY declare that a name is not a real file.

Make checks dependencies by comparing file modification times; if a prerequisite is newer than its target or the target is missing, the recipe runs. This enables incremental builds. The default shell is typically /bin/sh, and recipes run in that environment; the SHELL variable can modify this.

History and usage: Make and Makefiles originated on Unix in the 1970s and remain widely used, especially in C and C++ projects, though other build systems have become popular for other languages.