MAKE(1) (Extended Software Generation System Utilities) MAKE(1)
NAME
make - maintain, update, and regenerate groups of programs
SYNOPSIS
make [-f makefile] [-p] [-i] [-k] [-s] [-r] [-n] [-b] [-e]
[-u] [-t] [-q] [names]
DESCRIPTION
The make command allows the programmer to maintain, update,
and regenerate groups of computer programs. The following
is a brief description of all options and some special
names:
-f makefile Description filename. makefile is assumed to
be the name of a description file.
-p Print out the complete set of macro definitions
and target descriptions.
-i Ignore error codes returned by invoked
commands. This mode is entered if the fake
target name .IGNORE appears in the description
file.
-k Abandon work on the current entry if it fails,
but continue on other branches that do not
depend on that entry.
-s Silent mode. Do not print command lines before
executing. This mode is also entered if the
fake target name .SILENT appears in the
description file.
-r Do not use the built-in rules.
-n No execute mode. Print commands, but do not
execute them. Even lines beginning with an @
are printed.
-b Compatibility mode for old makefiles.
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-e Environment variables override assignments
within makefiles.
-t Touch the target files (causing them to be up-
to-date) rather than issue the usual commands.
-q Question. The make command returns a zero or
non-zero status code depending on whether the
target file is or is not up-to-date.
.DEFAULT If a file must be made but there are no
explicit commands or relevant built-in rules,
the commands associated with the name .DEFAULT
are used if it exists.
.PRECIOUS Dependents of this target will not be removed
when quit or interrupt are hit.
.SILENT Same effect as the -s option.
.IGNORE Same effect as the -i option.
make executes commands in makefile to update one or more
target names. Name is typically a program. If no -f option
is present, makefile, Makefile, and the Source Code Control
System (SCCS) files s.makefile, and s.Makefile are tried in
order. If makefile is -, the standard input is taken. More
than one -f makefile argument pair may appear.
make updates a target only if its dependents are newer than
the target. All prerequisite files of a target are added
recursively to the list of targets. Missing files are
deemed to be out-of-date.
makefile contains a sequence of entries that specify
dependencies. The first line of an entry is a blank-
separated, non-null list of targets, then a :, then a
(possibly null) list of prerequisite files or dependencies.
Text following a ; and all following lines that begin with a
tab are shell commands to be executed to update the target.
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The first non-empty line that does not begin with a tab or #
begins a new dependency or macro definition. Shell commands
may be continued across lines with the <backslash><new-line>
sequence. Everything printed by make (except the initial
tab) is passed directly to the shell as is. Thus,
echo a\
b
will produce
ab
exactly the same as the shell would.
Sharp (#) and new-line surround comments.
The following 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) and a common file
incl.h:
pgm: a.o b.o
cc a.o b.o -o pgm
a.o: incl.h a.c
cc -c a.c
b.o: incl.h b.c
cc -c b.c
Command lines are executed one at a time, each by its own
shell. The SHELL environment variable can be used to
specify which shell make should use to execute commands.
The default is /bin/sh. The first one or two characters in
a command can be the following: -, @, -@, or @-. If @ is
present, printing of the command is suppressed. If - is
present, make ignores an error. A line is printed when it
is executed unless the -s option is present, or the entry
.SILENT: is in makefile, or unless the initial character
sequence contains a @. The -n option specifies printing
without execution; however, if the command line has the
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string $(MAKE) in it, the line is always executed (see
discussion of the MAKEFLAGS macro under Environment). The
-t (touch) option updates the modified date of a file
without executing any commands.
Commands returning non-zero status normally terminate make.
If the -i option is present, or the entry .IGNORE: appears
in makefile, or the initial character sequence of the
command contains -, the error is ignored. If the -k option
is present, work is abandoned on the current entry, but
continues on other branches that do not depend on that
entry.
The -b option allows old makefiles (those written for the
old version of make) to run without errors.
Interrupt and quit cause the target to be deleted unless the
target is a dependent of the special name .PRECIOUS.
Environment
The environment is read by make. All variables are assumed
to be macro definitions and processed as such. The
environment variables are processed before any makefile and
after the internal rules; thus, macro assignments in a
makefile override environment variables. The -e option
causes the environment to override the macro assignments in
a makefile. Suffixes and their associated rules in the
makefile will override any identical suffixes in the built-
in rules.
The MAKEFLAGS environment variable is processed by make as
containing any legal input option (except -f and -p) defined
for the command line. Further, upon invocation, make
``invents'' the variable if it is not in the environment,
puts the current options into it, and passes it on to
invocations of commands. Thus, MAKEFLAGS always contains
the current input options. This proves very useful for
``super-makes''. In fact, as noted above, when the -n
option is used, the command $(MAKE) is executed anyway;
hence, one can perform a make -n recursively on a whole
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software system to see what would have been executed. This
is because the -n is put in MAKEFLAGS and passed to further
invocations of $(MAKE). This is one way of debugging all of
the makefiles for a software project without actually doing
anything.
Include Files
If the string include appears as the first seven letters of
a line in a makefile, and is followed by a blank or a tab,
the rest of the line is assumed to be a filename and will be
read by the current invocation, after substituting for any
macros.
Macros
Entries of the form string1 = string2 are macro definitions.
String2 is defined as all characters up to a comment
character or an unescaped new-line. Subsequent appearances
of $(string1[:subst1=[subst2]]) are replaced by string2.
The parentheses are optional if a single character macro
name is used and there is no substitute sequence. The
optional :subst1=subst2 is a substitute sequence. If it is
specified, all non-overlapping occurrences of subst1 in the
named macro are replaced by subst2. Strings (for the
purposes of this type of substitution) are delimited by
blanks, tabs, new-line characters, and beginnings of lines.
An example of the use of the substitute sequence is shown
under Libraries.
Internal Macros
There are five internally maintained macros that are useful
for writing rules for building targets.
$* The macro $* stands for the filename part of the
current dependent with the suffix deleted. It is
evaluated only for inference rules.
$@ The $@ macro stands for the full target name of the
current target. It is evaluated only for explicitly
named dependencies.
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$< The $< macro is only evaluated for inference rules or
the .DEFAULT rule. It is the module that is out-of-
date with respect to the target (i.e., the
``manufactured'' dependent file name). Thus, in the
.c.o rule, the $<
macro would evaluate to the .c file. An example for
making optimized .o files from .c files is:
.c.o:
cc -c -O $*.c
or:
.c.o:
cc -c -O $<
$? The $? macro is evaluated when explicit rules from the
makefile are evaluated. It is the list of
prerequisites that are out-of-date with respect to the
target; essentially, those modules which must be
rebuilt.
$% 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.
Four of the five macros can have alternative forms. When an
upper case D or F is appended to any of the four macros, the
meaning is changed to ``directory part'' for D and ``file
part'' for F. Thus, $(@D) refers to the directory part of
the string $@. If there is no directory part, ./ is
generated. The only macro excluded from this alternative
form is $?.
Suffixes
Certain names (for instance, those ending with .o) have
inferable prerequisites such as .c, .s, etc. If no update
commands for such a file appear in makefile, and if an
inferable prerequisite exists, that prerequisite is compiled
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to make the target. In this case, make has inference rules
which allow building files from other files by examining the
suffixes and determining an appropriate inference rule to
use. The current default inference rules are:
.c .c~ .f .f~ .sh .sh~
.c.o .c.a .c~.o .c~.c .c~.a
.f.o .f.a .f~.o .f~.f .f~.a
.h~.h .s.o .s~.o .s~.s .s~.a .sh~.sh
.l.o .l.c .l~.o .l~.l .l~.c
.y.o .y.c .y~.o .y~.y .y~.c
The internal rules for make are contained in the source file
rules.c for the make program. These rules can be locally
modified. To print out the rules compiled into the make on
any machine in a form suitable for recompilation, the
following command is used:
make -fp - 2>/dev/null </dev/null
A tilde in the above rules refers to an SCCS file [see
sccsfile(4)]. Thus, the rule .c~.o would transform an SCCS
C source file into an object file (.o). Because the s. of
the SCCS files is a prefix, it is incompatible with make's
suffix point of view. Hence, the tilde is a way of changing
any file reference into an SCCS file reference.
A rule with only one suffix (i.e., .c:) is the definition of
how to build x from x.c. In effect, the other suffix is
null. This is useful for building targets from only one
source file (e.g., shell procedures, simple C programs).
Additional suffixes are given as the dependency list for
.SUFFIXES. Order is significant; the first possible name
for which both a file and a rule exist is inferred as a
prerequisite. The default list is:
.SUFFIXES: .o .c .c~ .y .y~ .l .l~ .s .s~ .sh .sh~ .h .h~ .f
.f~
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Here again, the above command for printing the internal
rules will display the list of suffixes implemented on the
current machine. Multiple suffix lists accumulate;
.SUFFIXES: with no dependencies clears the list of suffixes.
Inference Rules
The first example can be done more briefly.
pgm: a.o b.o
cc a.o b.o -o pgm
a.o b.o: incl.h
This is because make has a set of internal rules for
building files. The user may add rules to this list by
simply putting them in the makefile.
Certain macros are used by the default inference rules to
permit the inclusion of optional matter in any resulting
commands. For example, CFLAGS, LFLAGS, and YFLAGS are used
for compiler options to cc(1), lex(1), and yacc(1),
respectively. Again, the previous method for examining the
current rules is recommended.
The inference of prerequisites can be controlled. The rule
to create a file with suffix .o from a file with suffix .c
is specified as an entry with .c.o: as the target and no
dependents. Shell commands associated with the target
define the rule for making a .o file from a .c file. Any
target that has no slashes in it and starts with a dot is
identified as a rule and not a true target.
Libraries
If a target or dependency name contains parentheses, it is
assumed to be an archive library, the string within
parentheses referring to a member within the library. Thus
lib(file.o) and $(LIB)(file.o) both refer to an archive
library that contains file.o. (This assumes the LIB macro
has been previously defined.) The expression $(LIB)(file1.o
file2.o) is not legal. Rules pertaining to archive
libraries have the form .XX.a where the XX is the suffix
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from which the archive member is to be made. An unfortunate
byproduct of the current implementation requires the XX to
be different from the suffix of the archive member. Thus,
one cannot have lib(file.o) depend upon file.o explicitly.
The most common use of the archive interface follows. Here,
we assume the source files are all C type source:
lib: lib(file1.o) lib(file2.o) lib(file3.o)
@echo lib is now up-to-date
.c.a:
$(CC) -c $(CFLAGS) $<
$(AR) $(ARFLAGS) $@ $*.o
rm -f $*.o
In fact, the .c.a rule listed above is built into make and
is unnecessary in this example. A more interesting, but
more limited example of an archive library maintenance
construction follows:
lib: lib(file1.o) lib(file2.o) lib(file3.o)
$(CC) -c $(CFLAGS) $(?:.o=.c)
$(AR) $(ARFLAGS) lib $?
rm $? @echo lib is now up-to-date
.c.a:;
Here the substitution mode of the macro expansions is used.
The $? list is defined to be the set of object filenames
(inside lib) whose C source files are out-of-date. The
substitution mode translates the .o to .c. (Unfortunately,
one cannot as yet transform to .c~; however, this may become
possible in the future.) Note also, the disabling of the
.c.a: rule, which would have created each object file, one
by one. This particular construct speeds up archive library
maintenance considerably. This type of construct becomes
very cumbersome if the archive library contains a mix of
assembly programs and C programs.
FILES
[Mm]akefile and s.[Mm]akefile
/bin/sh
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SEE ALSO
cc(1), lex(1), yacc(1), printf(3S), sccsfile(4).
cd(1), sh(1) in the User's Reference Manual.
NOTES
Some commands return non-zero status inappropriately; use -i
to overcome the difficulty.
BUGS
Filenames with the characters = : @ will not work. Commands
that are directly executed by the shell, notably cd(1), are
ineffectual across new-lines in make. The syntax
(lib(file1.o file2.o file3.o) is illegal. You cannot build
lib(file.o) from file.o. The macro $(a:.o=.c~) does not
work. Named pipes are not handled well.
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