@shorttitlepage GNU Make Copyright (C) 1988, '89, '90, '91, '92, '93, '94, '95 Free Software Foundation, Inc.

Published by the Free Software Foundation
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Cambridge, MA 02139 USA
Printed copies are available for $20 each.
ISBN 1-882114-50-7

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Free Software Foundation.

Cover art by Etienne Suvasa.

• Overview: Overview of make.
• Introduction: An introduction to make.
• Makefiles: Makefiles tell make what to do.
• Rules: Rules describe when a file must be remade.
• Commands: Commands say how to remake a file.
• Using Variables: You can use variables to avoid repetition.
• Conditionals: Use or ignore parts of the makefile based on the values of variables.
• Functions: Many powerful ways to manipulate text.
• make Invocation: How to invoke make on the command line.
• Implicit Rules: Use implicit rules to treat many files alike, based on their file names.
• Archives: How make can update library archives.
• Features: Features GNU make has over other makes.
• Missing: What GNU make lacks from other makes.
• Makefile Conventions: Conventions for makefiles in GNU programs.
• Quick Reference: A quick reference for experienced users.
• Complex Makefile: A real example of a straightforward, but nontrivial, makefile.
• Concept Index: Index of Concepts
• Name Index: Index of Functions, Variables, & Directives -- The Detailed Node Listing --- Overview of make
• Reading: On Reading this Text
• Bugs: Problems and Bugs An Introduction to Makefiles
• Rule Introduction: What a rule looks like.
• Simple Makefile: A Simple Makefile
• How Make Works: How make Processes This Makefile
• Variables Simplify: Variables Make Makefiles Simpler
• make Deduces: Letting make Deduce the Commands
• Combine By Dependency: Another Style of Makefile
• Cleanup: Rules for Cleaning the Directory Writing Makefiles
• Makefile Contents: What makefiles contain.
• Makefile Names: How to name your makefile.
• Include: How one makefile can use another makefile.
• MAKEFILES Variable: The environment can specify extra makefiles.
• Remaking Makefiles: How makefiles get remade.
• Overriding Makefiles: How to override part of one makefile with another makefile. Writing Rules
• Rule Syntax: General syntax explained.
• Wildcards: Using wildcard characters such as `*'.
• Directory Search: Searching other directories for source files.
• Phony Targets: Using a target that is not a real file's name.
• Force Targets: You can use a target without commands or dependencies to mark other targets as phony.
• Empty Targets: When only the date matters and the files are empty.
• Special Targets: Targets with special built-in meanings.
• Multiple Targets: When to make use of several targets in a rule.
• Multiple Rules: How to use several rules with the same target.
• Static Pattern: Static pattern rules apply to multiple targets and can vary the dependencies according to the target name.
• Double-Colon: How to use a special kind of rule to allow several independent rules for one target.
• Automatic Dependencies: How to automatically generate rules giving dependencies from the source files themselves. Using Wildcard Characters in File Names
• Wildcard Examples: Several examples
• Wildcard Pitfall: Problems to avoid.
• Wildcard Function: How to cause wildcard expansion where it does not normally take place. Searching Directories for Dependencies
• General Search: Specifying a search path that applies to every dependency.
• Selective Search: Specifying a search path for a specified class of names.
• Commands/Search: How to write shell commands that work together with search paths.
• Implicit/Search: How search paths affect implicit rules.
• Libraries/Search: Directory search for link libraries. Static Pattern Rules
• Static Usage: The syntax of static pattern rules.
• Static versus Implicit: When are they better than implicit rules? Writing the Commands in Rules
• Echoing: How to control when commands are echoed.
• Execution: How commands are executed.
• Parallel: How commands can be executed in parallel.
• Errors: What happens after a command execution error.
• Interrupts: What happens when a command is interrupted.
• Recursion: Invoking make from makefiles.
• Sequences: Defining canned sequences of commands.
• Empty Commands: Defining useful, do-nothing commands. Recursive Use of make
• MAKE Variable: The special effects of using `$(MAKE)'.
• Variables/Recursion: How to communicate variables to a sub-make.
• Options/Recursion: How to communicate options to a sub-make.
• -w Option: How the `-w' or `--print-directory' option helps debug use of recursive make commands. How to Use Variables
• Reference: How to use the value of a variable.
• Flavors: Variables come in two flavors.
• Advanced: Advanced features for referencing a variable.
• Values: All the ways variables get their values.
• Setting: How to set a variable in the makefile.
• Appending: How to append more text to the old value of a variable.
• Override Directive: How to set a variable in the makefile even if the user has set it with a command argument.
• Defining: An alternate way to set a variable to a verbatim string.
• Environment: Variable values can come from the environment. Advanced Features for Reference to Variables
• Substitution Refs: Referencing a variable with substitutions on the value.
• Computed Names: Computing the name of the variable to refer to. Conditional Parts of Makefiles
• Conditional Example: Example of a conditional
• Conditional Syntax: The syntax of conditionals.
• Testing Flags: Conditionals that test flags. Functions for Transforming Text
• Syntax of Functions: How to write a function call.
• Text Functions: General-purpose text manipulation functions.
• Filename Functions: Functions for manipulating file names.
• Foreach Function: Repeat some text with controlled variation.
• Origin Function: Find where a variable got its value.
• Shell Function: Substitute the output of a shell command. How to Run make
• Makefile Arguments: How to specify which makefile to use.
• Goals: How to use goal arguments to specify which parts of the makefile to use.
• Instead of Execution: How to use mode flags to specify what kind of thing to do with the commands in the makefile other than simply execute them.
• Avoiding Compilation: How to avoid recompiling certain files.
• Overriding: How to override a variable to specify an alternate compiler and other things.
• Testing: How to proceed past some errors, to test compilation.
• Options Summary: Summary of Options Using Implicit Rules
• Using Implicit: How to use an existing implicit rule to get the commands for updating a file.
• Catalogue of Rules: A list of built-in implicit rules.
• Implicit Variables: How to change what predefined rules do.
• Chained Rules: How to use a chain of implicit rules.
• Pattern Rules: How to define new implicit rules.
• Last Resort: How to defining commands for rules which cannot find any.
• Suffix Rules: The old-fashioned style of implicit rule.
• Search Algorithm: The precise algorithm for applying implicit rules. Defining and Redefining Pattern Rules
• Pattern Intro: An introduction to pattern rules.
• Pattern Examples: Examples of pattern rules.
• Automatic: How to use automatic variables in the commands of implicit rules.
• Pattern Match: How patterns match.
• Match-Anything Rules: Precautions you should take prior to defining rules that can match any target file whatever.
• Canceling Rules: How to override or cancel built-in rules. Using make to Update Archive Files
• Archive Members: Archive members as targets.
• Archive Update: The implicit rule for archive member targets.
• Archive Suffix Rules: You can write a special kind of suffix rule for updating archives. Implicit Rule for Archive Member Targets
• Archive Symbols: How to update archive symbol directories.

Overview of make

The make utility automatically determines which pieces of a large program need to be recompiled, and issues commands to recompile them. This manual describes GNU make, which was implemented by Richard Stallman and Roland McGrath. GNU make conforms to section 6.2 of IEEE Standard 1003.2-1992 (POSIX.2).

Our examples show C programs, since they are most common, but you can use make with any programming language whose compiler can be run with a shell command. Indeed, make is not limited to programs. You can use it to describe any task where some files must be updated automatically from others whenever the others change.

• Reading: On Reading this Text
• Bugs: Problems and Bugs

To prepare to use make, you must write a file called the makefile that describes the relationships among files in your program and provides commands for updating each file. In a program, typically, the executable file is updated from object files, which are in turn made by compiling source files.

Once a suitable makefile exists, each time you change some source files, this simple shell command:

make

suffices to perform all necessary recompilations. The make program uses the makefile data base and the last-modification times of the files to decide which of the files need to be updated. For each of those files, it issues the commands recorded in the data base.

You can provide command line arguments to make to control which files should be recompiled, or how. See section How to Run make.

How to Read This Manual

If you are new to make, or are looking for a general introduction, read the first few sections of each chapter, skipping the later sections. In each chapter, the first few sections contain introductory or general information and the later sections contain specialized or technical information. The exception is section An Introduction to Makefiles, all of which is introductory.

If you are familiar with other make programs, see section Features of GNU make, which lists the enhancements GNU make has, and section Incompatibilities and Missing Features, which explains the few things GNU make lacks that others have.

For a quick summary, see section Summary of Options, section Quick Reference, and section Special Built-in Target Names.

Problems and Bugs

If you have problems with GNU make or think you've found a bug, please report it to the developers; we cannot promise to do anything but we might well want to fix it.

Before reporting a bug, make sure you've actually found a real bug. Carefully reread the documentation and see if it really says you can do what you're trying to do. If it's not clear whether you should be able to do something or not, report that too; it's a bug in the documentation!

Before reporting a bug or trying to fix it yourself, try to isolate it to the smallest possible makefile that reproduces the problem. Then send us the makefile and the exact results make gave you. Also say what you expected to occur; this will help us decide whether the problem was really in the documentation.

Once you've got a precise problem, please send electronic mail either through the Internet or via UUCP:

Internet address:
    bug-gnu-utils@prep.ai.mit.edu

UUCP path:
    mit-eddie!prep.ai.mit.edu!bug-gnu-utils

Please include the version number of make you are using. You can get this information with the command `make --version'. Be sure also to include the type of machine and operating system you are using. If possible, include the contents of the file `config.h' that is generated by the configuration process.

Non-bug suggestions are always welcome as well. If you have questions about things that are unclear in the documentation or are just obscure features, send a message to the bug reporting address. We cannot guarantee you'll get help with your problem, but many seasoned make users read the mailing list and they will probably try to help you out. The maintainers sometimes answer such questions as well, when time permits.