NAME

make − maintain, update, and regenerate groups of programs

SYNOPSIS

make [ −f makefile ] ... [ −deikmnpqrsStb ] [ target ... ] [ macro-name=value ... ]

DESCRIPTION

make executes a list of shell commands associated with each target, typically to create or update a file of the same name.  makefile contains entries for targets that describe how to bring them up to date with respect to the files and/or other targets on which each depends, called dependencies. 

A target is out of date when the file it describes is missing, or when one (or more) of its dependency files has a more recent modification time than that of the target file.  make recursively scans the list of dependencies for each target argument (or the first target entry in the makefile if no target argument is supplied) to generate a list of targets to check.  It then checks, from the bottom up, each target against any files it depends on to see if it is out of date.  If so, make rebuilds that target. 

To rebuild a target, make executes the set of shell commands, called a rule, associated with it.  This rule may be listed explicitly in a makefile entry for that target, or it may be supplied implicitly by make. 

If no makefile is specified on the command line, make uses the first file it finds with a name from the following list:

makefile, Makefile, s.makefile, s.Makefile, SCCS/s.makefile, SCCS/s.Makefile

If no target is specified on the command line, make uses the first target defined in makefile.  If a target has no makefile entry, or if its entry has no rule, make attempts to update that target using an implicit rule. 

OPTIONS

−f makefile
Use the description file makefile.  A − as the makefile argument denotes the standard input.  The contents of makefile, when present, override the builtin rules.  When more than one −f makefile argument pairs appear, make takes input from each makefile in the order listed (just as if they were run through cat(1V)).

−d Debug mode.  Print out detailed information on files and times examined. 

−e Environment variables override assignments within makefiles. 

−i Ignore error codes returned by invoked commands. 

−k When a nonzero error status is returned by an invoked command, abandon work on the current target but continue with other branches that do not depend on that target. 

−n No execution mode.  Print commands, but do not execute them.  Even lines beginning with an @ are printed.  However, if a command line contains the $(MAKE) macro, that line is always executed (see the discussion of MAKEFLAGS in Environment Variables and Macros).

−p Print out the complete set of macro definitions and target descriptions. 

−q Question mode.  make returns a zero or nonzero status code depending on whether or not the target file is up to date. 

−r Do not use the the implicit rules make supplies by default.  Implicit rules defined in the makefile remain in effect. 

−s Silent mode.  Do not print command lines before executing them. 

−S Undo the effect of the −k option. 

−t Touch the target files (bringing them up to date) rather than performing commands listed in their rules. 

−b This option has no effect, but is present for compatibility reasons. 

macro-name=value
Macro definition.  This definition overrides any definition for the specified macro that occurs in the makefile itself, or in the environment.  See Macros and Environment Variables and Macros, for details. 

USAGE

Refer to Doing More With UNIX: Beginner’s Guide, and Make in Programming Utilities for the Sun Workstation for tutorial information about make. 

Targets and Rules

There need not be an actual file named by a target, but every dependency in the dependency list must be either the name of a file, or the name of another target. 

If the target has no dependency list and no rule, or if the target has no entry in the makefile, make attempts to produce an entry by selecting a rule from its its set of implicit rules.  If none of the implicit rules apply, make uses the rule specified in the .DEFAULT target (if it appears in the makefile).  Otherwise make stops and produces an error message. 

Makefile Target Entries

A target entry has the following format:

target ... : [dependency] ... [; command] ...

[command]
...

The first line contains the name of a target (or a space-separated list of target names), terminated with a colon (:).  This may be followed by a dependency, or a dependency list that make checks in the order listed.  The dependency list may be terminated with a semicolon (;), which in turn can be followed by a Bourne shell command.  Subsequent lines in the target entry begin with a TAB, and contain Bourne shell commands.  These commands comprise a rule for building the target, and are performed when the target is updated by make. 

Shell commands may be continued across input lines by escaping the NEWLINE with a backslash (\).  The continuing line must also start with a TAB. 

To rebuild a target, make expands any macros, strips off initial TABs and passes each resulting command line to a Bourne shell for execution. 

The first nonblank line that does not begin with a TAB or # begins another target or macro definition. 

Makefile Special Characters

:: Conditional dependency branch.  When used in place of a colon (:) the double-colons allow a target to be checked and updated with respect to more than one dependency list.  The double-colons allow the target to have more than one branch entry in the makefile, each with a different dependency list and a different rule.  make checks each branch, in order of appearance, to see if the target is outdated with respect to its dependency list.  If so, make updates the target according to dependencies and rule for that branch. 

# Start a comment.  The comment ends at the next NEWLINE. 

$ Macro expansion.  See Macros, below, for details. 

− Following the TAB, if the first character of a command line is a −, make ignores any nonzero error code it may return.  make normally terminates when a command returns nonzero status, unless the −i or −k options are in effect. 

@ Following the TAB, if the first character is a @, make does not print the command line before executing it. 

If − and @ appear as the first two characters after the TAB, both apply. 

$$ The dollar-sign, escaped from macro expansion.  Can be used to pass variable expressions beginning with $ to the shell. 

Command Execution

Command lines are executed one at a time, each by its own shell.  Shell commands, notably cd, are ineffectual across an unescaped NEWLINE in the makefile.  A line is printed (after macro expansion) as it is executed, unless it starts with a @, there is a .SILENT entry in the dependency hierarchy of the current target, or make is run with the −s option.  Although the −n option specifies printing without execution, lines containing the macro $(MAKE) are executed regardless, and lines containing the @ special character are printed.  The −t (touch) option updates the modification date of a file without executing any rules.  This can be dangerous when sources are maintained by more than one person. 

To take advantage of the Bourne shell if control statement, use a command line of the form:

if expression ; \
then command ; \
command ; \
...
elif command ; \
...
else command ; \
fi

Although composed of several input lines, the escaped NEWLINEs insure that make treats them all as one command line.  To take advantage of the Bourne shell for control statement, use a command line of the form:

for var in list ; do \
command ; \
...
done

To write shell variables, use double dollar-signs ($$).  This escapes expansion of the dollar-sign by make. 

Signals

INT and QUIT signals received from the keyboard cause make to halt, and to remove the target file being processed (unless it is in the dependency list for .PRECIOUS). 

Special-Function Targets

When incorporated in a makefile, the following target names perform special functions. 

.DEFAULT If this target is defined in the makefile, its rule is used when there is no entry in the makefile for a given target and none of the implicit rules applies.  make ignores the dependency list for this target. 

.PRECIOUS List of files not to delete.  Files listed as dependencies for this target are not removed if make is interrupted while rebuilding them. 

.SILENT Run silently.  When this target appears in the makefile, make does not echo commands before executing them. 

.IGNORE Ignore errors.  When this target appears in the makefile, make ignores nonzero error codes returned from commands. 

.SUFFIXES The suffixes list for selecting implicit rules (see Implicit Rules).

Include Files

make has an include file capability.  If the word include appears as the first seven letters of a line, and is followed by a SPACE or a TAB, the string that follows is taken as a filename.  The text of the named file is read in at the current location in the makefile.  include files can be nested to a depth of no more than about 16. 

Macros

Entries of the form

macro-name= value

define macros.  name is the name of the macro, and value, which consists of all characters up to a comment character or unescaped NEWLINE, is the value.  Words in a macro value are delimited by SPACE, TAB, and escaped NEWLINE characters, and the terminating NEWLINE. 

Subsequent references to the macro, of the forms: $(name) or ${name} are replaced by value. The parentheses or brackets can be omitted in a reference to a macro with a single-character name.

Macros definitions can contain references to other macros, but the nested references aren’t expanded immediately.  Instead, they are expanded along with references to the macro itself. 

Substitutions within macros can be made as follows:

$(name:str1=str2)

where str1 is either a suffix, or a word to be replaced in the macro definition, and str2 is the replacement suffix or word. 

Dynamically Maintained Macros

There are several dynamically maintained macros that are useful as abbreviations within rules. 

$∗ The basename of the current target.  It is assigned only for implicit rules. 

$< The name of the file on which the target is assumed to depend.  This macro is only assigned for implicit rules, or within the .DEFAULT target’s rule. 

$@ The name of the current target.  It is assigned only for rules in targets that are explicitly defined in the makefile. 

$?  The list of dependencies with respect to which the target is out of date.  This macro is assigned only for explicit rules. 

$% The library member.  The $% macro is only evaluated when the target is an archive library member of the form: lib(file.o).  In this case, $@ evaluates to lib and $% evaluates to the library member, file.o.

All of these macros but $?  can be modified to apply either to the filename part, or the directory part of the strings they stand for, by adding an upper case F or D, respectively (and enclosing the resulting name in parentheses or braces).  Thus, $(@D) refers to the directory part of the string $@.  If there is no directory part, .  is generated. 

Environment Variables and Macros

After reading in its implicit rules, make reads in variables from the environment, treating them as if they were macro definitions.  Only then does make read in a makefile.  Thus, macro assignments within a makefile override environment variables, provided that the −e option is not in effect.  In turn, make exports environment variables to each shell it invokes.  Macros not read in from the environment are not exported. 

The MAKEFLAGS macro is a special case.  When present as an environment variable, make takes its options (except for −f, −p, and −d) from MAKEFLAGS, in combination with any flags entered on the command line.  make retains this combined value, exports it automatically to each shell it forks, and reads its value to obtain options for any make commands it invokes.  Note, however that flags passed with MAKEFLAGS, even though they are in effect, are not shown in the output produced by make. 

The MAKE macro is another special case.  It has the value "make" by default, and temporarily overrides the −n option for any line that contains a reference to it.  This allows nested invocations of make written as:

$(MAKE) ...

to run recursively, so that the command make −n can be used to test an entire hierarchy of makefiles. 

For compatibility with the 4.2 BSD make, the MFLAGS macro is set from the MAKEFLAGS variable by prepending a “−”.  MFLAGS is not exported automatically. 

make supplies the following macros for compilers and their options:

CC	C compiler, cc(1V)	CFLAGS	C compiler options
FC	FORTRAN 77 compiler, f77(1)	FFLAGS	FORTRAN 77 compiler options
		RFLAGS	FORTRAN 77 compiler options with Ratfor (.r) source files
PC	Pascal compiler, pc(1)	PFLAGS	Pascal compiler options
M2C	Modula-2 compiler	M2FLAGS	Modula-2 compiler options
GET	sccs(1) get command	GFLAGS	sccs get options
AS	the assembler, as(1)	ASFLAGS	assembler options
LD	the linker, ld(1)	LDFLAGS	linker options
LEX	lex(1)	LFLAGS	lex options
YACC	yacc(1)	YFLAGS	yacc options

Unless these macros are  read in as environment variables, their values are not exported by make.  If you run make with any these set in the environment, it is a good idea to add commentary to the makefile to indicate what value each takes.  If −r is in effect, make ignores these macro definitions. 

When set to a single-word value such as /bin/csh, the SHELL macro indicates the name of an alternate shell to use for invoking commands.  Note, however, that to improve normal performance make executes command lines that contain no shell metacharacters directly.  Such builtin commands as dirs, or set in the C-Shell are not recognized unless the command line includes a metacharacter (for instance, a semicolon). 

Implicit Rules

make supplies implicit rules for certain types of targets that have no explicit rule defined in the makefile.  For these types of targets, make attempts to select an implicit rule by looking for an association between the target and a file in the directory that shares its basename.  That file, if found, is presumed to be a dependency file.  The implicit rule is selected according to the target’s suffix (which may be null), and that of the dependency file.  If there is no such dependency file, if the suffix of either dependency or target is not the suffixes list, or if there is no implicit rule defined for that pair of suffixes, no rule is selected.  make either uses the default rule that you have supplied (if any), or stops. 

The suffixes list is a target with each known suffix listed as a dependency, by default:

.SUFFIXES: .o  .c  .c∼  .mod  .mod∼  .sym  .def  .def∼  .p .p∼  .f  .f∼  .r  .r∼  .y  .y∼  .l  .l∼ .s  .s∼  .sh  .sh∼  .h  .h∼

Multiple suffix-list targets accumulate; a .SUFFIXES target with no dependencies clears the list of suffixes.  Order is significant; make selects a rule that corresponds to the target’s suffix and the first dependency-file suffix found in the list. 

A tilde (∼) refers to the s.  prefix of an SCCS history file (see sccs(1)). If make cannot locate a history file (with a name of the form s.basename.suffix) in the current working directory, it checks for one in the SCCS subdirectory (if that directory exists) for one from which to get(1) the dependency file.

An implicit rule is a target of the form:

dt:

rule

where t is the suffix of the target, d is the suffix of the dependency, and rule is the implicit rule for building such a target from such a dependency.  Both d and t must appear in the suffixes list for make to recognize the target as one that defines an implicit rule. 

An implicit rule with only one suffix describes how to build a target having a null (or no) suffix, from a dependency having the indicated suffix.  For instance, the .c rule describes how to build the executable file from a C source file, file.c. 

Implicit rules are supplied for the following suffixes and suffix pairs:

.c  .c∼  .p  .p∼  .mod  .mod∼  .f  .f∼  .F  .F∼  .r  .r∼ .sh  .sh∼ .c.o  .c∼.o  .c∼.c  .p.o  .p∼.o  .p∼.p  .mod.o  .mod∼.o .mod∼.mod .def.sym  .def∼.sym  .def∼.def .f.o  .f∼.f  .F.o  .F∼.o .F∼.F .r.o  .r∼.o  .r∼.r  .s.o  .s∼.o .s∼.s .sh∼.sh .y.o .y∼.o  .l.o  .l∼.o .y.c  .y∼.c  .y∼.y  .l.c  .l∼.c  .l∼.l  .c.a  .c∼.a .s∼.a  .h∼.h

These rules can be changed within a makefile, and additional implicit rules can be added.  To print out make’s internal rules, use the following command (note that this command only works with the Bourne Shell):

$  make −fp − 2>/dev/null </dev/null

If you are using the C-Shell, use this command to print out make’s internal rules:

host%  (make −fp − </dev/null >/dev/tty) >&/dev/null

Library Maintenance

If a target name contains parentheses, as with:

lib.a(member)

it is assumed to be the name of an archive (ar(1)) library.  The string within the parentheses refers to a member of the library.  (If the string contains more than one word, the only first word is used.) A member of an archive can be explicitly made to depend on a file with a matching filename.  For instance, given a directory that contains the files mem1.c and mem2.c, along with a makefile with the entries:

lib.a: lib.a(mem1.o) lib.a(mem2.0)

lib.a(mem1.o): mem1.o
ar rv lib.a mem1.o

lib.a(mem2.o): mem2.o
ar rv lib.a mem2.o

make, when run, compiles the .c files into relocatable object (.o) files using the .c.o implicit rule.  It then loads the freshly compiled version of each file into the library according to the explicit rules in the ‘lib.a()’ targets. 

Implicit rules pertaining to archive libraries have the form .XX.a where the XX is the suffix from which the archive member is to be made.  An unfortunate byproduct of the current implementation requires that XX to be different from the suffix of the archive member itself.  For instance, the target lib(file.o) cannot depend upon the file.o explicitly, but instead, must be made to depend on a source file, such as file.c.  For this reason it is recommended that you define an explicit target in the makefile for each library member to maintain, as shown above. 

A target name of the form

library((entry-point))

refers to the member of a randomized object library (see ranlib(1)) that defines the symbol entry-point. 

EXAMPLES

This makefile says that pgm depends on two files a.o and b.o, and that they in turn depend on their corresponding source files (a.c and b.c) along with a common file incl.h:

pgm: a.o b.o
cc a.o b.o −o $@

a.o: incl.h a.c
cc −c a.c

b.o: incl.h b.c
cc −c b.c

The following makefile uses the builtin inference rules to express the same dependencies:

pgm: a.o b.o
cc a.o b.o −o pgm

a.o b.o: incl.h

FILES

[Mm]akefile
s.[Mm]akefile
SCCS/s.[mM]akefile

DIAGNOSTICS

Don’t know how to make target. Stop.
There is no makefile entry for target, and none of make’s implicit rules apply (there is no dependency file with a suffix in the suffixes list, or the target’s suffix is not in the list).

∗∗∗ target removed. 
make was interrupted in the middle of trying to build target.  Rather than leaving a partially-completed version that is newer than its dependencies, make removes the file associated with target. 

∗∗∗ Error code n. 
The previous shell command returned a nonzero error code. In this case make stops, unless either the −k or the −i option is set, the target .IGNORE appears, or the command is prefixed with a − in the makefile. 

SEE ALSO

cc(1V), ar(1), cd(1), get(1), lex(1), ranlib(1), sh(1), sccs(1)

Doing More with UNIX: Beginner’s Guide

Make, in Programming Utilities for the Sun Workstation

BUGS

Some commands return nonzero status inappropriately; use −i to overcome the difficulty. 

Filenames with the characters = : @ will not work. 

You cannot build lib(file.o) from file.o. 

The macro substitution $(a:.o=.c~) does not work. 

Options supplied by MAKEFLAGS should appear in output from make. 

Sun Release 3.2  —  Last change: 19 June 1986