#Write simple makefile for c program update#
#Write simple makefile for c program code#
#Write simple makefile for c program series#

If any of the prerequisites has an associated rule, make attempts to update those first. When make is asked to evaluate a rule, it begins by finding the files indicated by the prerequisites and target. The command script usually appears on the following lines and is preceded by a tab character. The prerequisites foo.c and foo.h appear after the colon. The target file foo.o appears before the colon.

Here is a rule for compiling a C file, foo.c, into an object file, foo.o: foo.o: foo.c foo.h And the commands are those shell commands that will create the target from the prerequisites. The prerequisites or dependents are those files that must exist before the target can be successfully created. The target is the file or thing that must be made. A rule consists of three parts: the target, its prerequisites, and the command(s) to perform: target: prereq 1 prereq 2 commands The first rule seen by make is used as the default rule. Furthermore, make is flexible enough to be used anywhere one kind of file depends on another from traditional programming in C/C++ to Java, T EX, database management, and more.Įssentially a makefile contains a set of rules used to build an application.

#Write simple makefile for c program series#

So the principle value of make comes from its ability to perform the complex series of commands necessary to build an application and to optimize these operations when possible to reduce the time taken by the edit-compile-debug cycle. The specification file, or makefile, describes the relationship between the source, intermediate, and executable program files so that make can perform the minimum amount of work necessary to update the executable.

#Write simple makefile for c program code#

Modifying any of the source files and reinvoking make will cause some, but usually not all, of these commands to be repeated so the source code changes are properly incorporated into the executable. Then, for C/C++, the object files are bound together by a linker (usually invoked through the compiler, gcc) to form an executable program. Next the source is compiled into binary object files (. Often the source code for the program is incomplete and the source must be generated using utilities such as flex or bison. Typically the default goal in most makefiles is to build a program.

If no command-line targets are given, then the first target in the file is used, called the default goal. If a target is included as a command-line argument, that target is updated. This will cause the make program to read the makefile and build the first target it finds there: $ make To build the program execute make by typing: $ makeĪt the command prompt of your favorite shell. Here is a makefile to build the traditional “Hello, World” program: hello: hello.c The specification that make uses is generally saved in a file named makefile. In short, make can be considered the center of the development process by providing a roadmap of an application’s components and how they fit together. It also provides features to manage alternate configurations, implement reusable libraries of specifications, and parameterize processes with user-defined macros. make defines a language for describing the relationships between source code, intermediate files, and executables. GNU make (and other variants of make) do precisely this. Using this information, make can also optimize the build process avoiding unnecessary steps. The advantages of make over scripts is that you can specify the relationships between the elements of your program to make, and it knows through these relationships and timestamps exactly what steps need to be redone to produce the desired program each time.

The make program is intended to automate the mundane aspects of transforming source code into an executable. Moreover, as the program’s complexity grows these mundane tasks can become increasingly error-prone as different versions of the program are developed, perhaps for other platforms or other versions of support libraries, etc. Later they discover that they were never executing their modified function because of some procedural error such as failing to recompile the source, relink the executable, or rebuild a jar. Most developers have experienced the frustration of modifying a function and running the new code only to find that their change did not fix the bug. Although transforming the source into an executable is considered routine, if done incorrectly a programmer can waste immense amounts of time tracking down the problem. The mechanics of programming usually follow a fairly simple routine of editing source files, compiling the source into an executable form, and debugging the result. Chapter 1. How to Write a Simple Makefile