Appendix A Quick Reference

This appendix summarizes the directives, text manipulation functions, and special variables which GNU make understands. See Special Targets, Catalogue of Implicit Rules, and Summary of Options, for other summaries.

Here is a summary of the directives GNU make recognizes:

define variable

endef

Define a multi-line, recursively-expanded variable.
See Sequences.

ifdef variable

ifndef variable

ifeq (a,b)

ifeq "a" "b"

ifeq 'a' 'b'

ifneq (a,b)

ifneq "a" "b"

ifneq 'a' 'b'

else

endif

Conditionally evaluate part of the makefile.
See Conditionals.

include file

-include file

sinclude file

Include another makefile.
See Including Other Makefiles.

override variable = value

override variable := value

override variable += value

override variable ?= value

override define variable

endef

Define a variable, overriding any previous definition, even one from the command line.
See The override Directive.

export

Tell make to export all variables to child processes by default.
See Communicating Variables to a Sub-make.

export variable

export variable = value

export variable := value

export variable += value

export variable ?= value

unexport variable

Tell make whether or not to export a particular variable to child processes.
See Communicating Variables to a Sub-make.

vpath pattern path

Specify a search path for files matching a ‘%’ pattern.
See The vpath Directive.

vpath pattern

Remove all search paths previously specified for pattern.

vpath

Remove all search paths previously specified in any vpath directive.

Here is a summary of the built-in functions (see Functions):

$(subst from,to,text)

Replace from with to in text.
See Functions for String Substitution and Analysis.

$(patsubst pattern,replacement,text)

Replace words matching pattern with replacement in text.
See Functions for String Substitution and Analysis.

$(strip string)

Remove excess whitespace characters from string.
See Functions for String Substitution and Analysis.

$(findstring find,text)

Locate find in text.
See Functions for String Substitution and Analysis.

$(filter pattern...,text)

Select words in text that match one of the pattern words.
See Functions for String Substitution and Analysis.

$(filter-out pattern...,text)

Select words in text that do not match any of the pattern words.
See Functions for String Substitution and Analysis.

$(sort list)

Sort the words in list lexicographically, removing duplicates.
See Functions for String Substitution and Analysis.

$(word n,text)

Extract the nth word (one-origin) of text.
See Functions for String Substitution and Analysis.

$(words text)

Count the number of words in text.
See Functions for String Substitution and Analysis.

$(wordlist s,e,text)

Returns the list of words in text from s to e.
See Functions for String Substitution and Analysis.

$(firstword names...)

Extract the first word of names.
See Functions for String Substitution and Analysis.

$(lastword names...)

Extract the last word of names.
See Functions for String Substitution and Analysis.

$(dir names...)

Extract the directory part of each file name.
See Functions for File Names.

$(notdir names...)

Extract the non-directory part of each file name.
See Functions for File Names.

$(suffix names...)

Extract the suffix (the last ‘.’ and following characters) of each file name.
See Functions for File Names.

$(basename names...)

Extract the base name (name without suffix) of each file name.
See Functions for File Names.

$(addsuffix suffix,names...)

Append suffix to each word in names.
See Functions for File Names.

$(addprefix prefix,names...)

Prepend prefix to each word in names.
See Functions for File Names.

$(join list1,list2)

Join two parallel lists of words.
See Functions for File Names.

$(wildcard pattern...)

Find file names matching a shell file name pattern (not a ‘%’ pattern).
See The Function wildcard.

$(realpath names...)

For each file name in names, expand to an absolute name that does not contain any ., .., nor symlinks.
See Functions for File Names.

$(abspath names...)

For each file name in names, expand to an absolute name that does not contain any . or .. components, but preserves symlinks.
See Functions for File Names.

$(error text...)

When this function is evaluated, make generates a fatal error with the message text.
See Functions That Control Make.

$(warning text...)

When this function is evaluated, make generates a warning with the message text.
See Functions That Control Make.

$(shell command)

Execute a shell command and return its output.
See The shell Function.

$(origin variable)

Return a string describing how the make variable variable was defined.
See The origin Function.

$(flavor variable)

Return a string describing the flavor of the make variable variable.
See The flavor Function.

$(foreach var,words,text)

Evaluate text with var bound to each word in words, and concatenate the results.
See The foreach Function.

$(call var,param,...)

Evaluate the variable var replacing any references to $(1), $(2) with the first, second, etc. param values.
See The call Function.

$(eval text)

Evaluate text then read the results as makefile commands. Expands to the empty string.
See The eval Function.

$(value var)

Evaluates to the contents of the variable var, with no expansion performed on it.
See The value Function.

Here is a summary of the automatic variables. See Automatic Variables, for full information.

$@

The file name of the target.

$%

The target member name, when the target is an archive member.

$<

The name of the first prerequisite.

$?

The names of all the prerequisites that are newer than the target, with spaces between them. For prerequisites which are archive members, only the member named is used (see Archives).

$^

$+

The names of all the prerequisites, with spaces between them. For prerequisites which are archive members, only the member named is used (see Archives). The value of $^ omits duplicate prerequisites, while $+ retains them and preserves their order.

$*

The stem with which an implicit rule matches (see How Patterns Match).

$(@D)

$(@F)

The directory part and the file-within-directory part of $@.

$(*D)

$(*F)

The directory part and the file-within-directory part of $*.

$(%D)

$(%F)

The directory part and the file-within-directory part of $%.

$(<D)

$(<F)

The directory part and the file-within-directory part of $<.

$(^D)

$(^F)

The directory part and the file-within-directory part of $^.

$(+D)

$(+F)

The directory part and the file-within-directory part of $+.

$(?D)

$(?F)

The directory part and the file-within-directory part of $?.

These variables are used specially by GNU make:

MAKEFILES

Makefiles to be read on every invocation of make.
See The Variable MAKEFILES.

VPATH

Directory search path for files not found in the current directory.
See VPATH Search Path for All Prerequisites.

SHELL

The name of the system default command interpreter, usually /bin/sh. You can set SHELL in the makefile to change the shell used to run commands. See Command Execution. The SHELL variable is handled specially when importing from and exporting to the environment. See Choosing the Shell.

MAKESHELL

On MS-DOS only, the name of the command interpreter that is to be used by make. This value takes precedence over the value of SHELL. See MAKESHELL variable.

MAKE

The name with which make was invoked. Using this variable in commands has special meaning. See How the MAKE Variable Works.

MAKELEVEL

The number of levels of recursion (sub-makes).
See Variables/Recursion.

MAKEFLAGS

The flags given to make. You can set this in the environment or a makefile to set flags.
See Communicating Options to a Sub-make.

It is never appropriate to use MAKEFLAGS directly on a command line: its contents may not be quoted correctly for use in the shell. Always allow recursive make's to obtain these values through the environment from its parent.

MAKECMDGOALS

The targets given to make on the command line. Setting this variable has no effect on the operation of make.
See Arguments to Specify the Goals.

CURDIR

Set to the pathname of the current working directory (after all -C options are processed, if any). Setting this variable has no effect on the operation of make.
See Recursive Use of make.

SUFFIXES

The default list of suffixes before make reads any makefiles.

.LIBPATTERNS

Defines the naming of the libraries make searches for, and their order.
See Directory Search for Link Libraries.