make - Maintains, updates, and regenerates groups of programs.
make [-f makefile] [options] [names]
Compatibility mode for old makefiles. Debug mode. Displays
detailed information on files and times examined.
Causes environment variables to override assignments
within makefiles. Uses the specified description file
name. A file name of - denotes the standard input. The
contents of the file specified as makefile override the
built-in rules. Ignores error codes returned by invoked
commands. This mode is entered if the special target name
.IGNORE appears in the description file. Stops work on
the current entry, but continues on other branches that do
not depend on that entry. No execute mode. Displays commands,
but does not execute them. Even lines beginning
with an at sign (@) are displayed. Displays the complete
set of macro definitions and target descriptions. Question
mode. Returns a zero or nonzero status code depending
on whether the target file is or is not up to date.
Does not use the built-in rules. Silent mode. Suppresses
the display of command lines before executing. This mode
is also entered if the special target name .SILENT appears
in the description file. Abandons work on the current
entry if it fails; the opposite of the -k option. If both
options are specified, the last one specified on the command
line is used. Touches target files (causing them to
be up to date) rather than issuing the usual commands.
This make command is one of several versions available.
See the SEE ALSO section for references to information
about other versions of the command. By default, the
make(1) command is invoked if you type the command name
with no path. To access the make(1u) version described in
this reference page, use the following command path:
The make program is designed to simplify the maintenance
of other programs. This is the SYSTEM V version of the
make command with some Berkeley compatibility added.
The make program executes commands in makefile to update
one or more target names. The name argument is typically
a program. If no -f option is present, makefile, Makefile,
s.makefile, and s.Makefile are tried in order. If
makefile is -, the standard input is taken. You can specify
more than one -f makefile argument.
The make program 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Missing files are deemed to be out of date.
The makefile argument 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 colon
(:), then a (possibly null) list of prerequisite files or
dependencies. Text following a semicolon (;) and all following
lines that begin with a tab are shell commands to
be executed to update the target. The first line that does
not begin with a tab or number sign (#) begins a new
dependency or macro definition. Shell commands can be
continued across lines with the backslash followed by a
new-line (RET) sequence. Everything printed by make
(except the initial tab) is passed directly to the shell.
For example: echo a\ b
These entries produce the following:
This output is exactly the same as what would have been
produced by the shell.
The Number sign (#) 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
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 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 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 string $(MAKE) in it,
the line is always executed. (See the discussion of the
MAKEFLAGS macro under the Environment section). The -t
(touch) option updates the modified date of a file without
executing any commands.
Commands returning nonzero status normally terminate make.
If the -i option is present, or the entry appears in makefile,
or the initial character sequence of the command
contains -, the error is ignored. If the -k option is
present, work stops 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. The difference
between the old version of make and this version is
that this version requires all dependency lines to have a
(possibly null or implicit) command associated with them.
The previous version of make assumed, if no command was
specified explicitly, that the command was null.
Interrupt and quit cause the target to be deleted unless
the target is a dependent of the special name
Environment [Toc] [Back]
The environment is always read by make. All variables are
assumed to be macro definitions and processed as such. The
-e option causes the environment to override the macro
assignments in a makefile.
The make command operates in three compatibility modes.
The type of mode is determined by the value of the
PROG_ENV environment variable and by the way that make is
executed. The PROG_ENV variable has two valid values: BSD
In BSD mode, make executes with Berkeley compatibility.
This means that /bin/sh is always used as the command
interpreter regardless of the value of SHELL, and the commands
are echoed to standard out without a prefixed <tab>.
In POSIX mode, make executes with POSIX compatibility,
such that the SHELL environment variable is always
ignored, SHELL is always overridden by MAKESHELL, the
shell is always used to execute commands, and commands are
echoed to standard out with a prefixed <tab>.
The MAKEFLAGS environment variable is processed by make as
containing any legal input option (except -f, -p, and -d)
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 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
Macros [Toc] [Back]
Macros can be defined in four different ways. Some macros
are defined by default by make internally. All environment
variables are assumed to be macro definitions and
macros can be defined in the makefile as well as on the
make command line. By default, the internal default
macros are overridden by environment variables, macros
defined in the makefile override environment variables and
macros defined on the command line override macros defined
in the makefile. The -e option changes this such that
environment variables override macros defined in the makefile.
Entries of the form string1 = string2 are macro definitions.
The 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 : subst1i = subst2 is a
substitute sequence. If it is specified, all non-overlapping
occurrences of subst1 in the named macro are replaced
by subst2. The occurrence of subst1 must be a suffix at
the end of the word string1. 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 in the
The MACHINE macro is defined by make to allow for machine
independent makefiles. The default string for MACHINE is
"vax", "mips", or "alpha", according to which machine the
application is running on. You can redefine MACHINE to one
of the other strings for cross development work.
Internal Macros [Toc] [Back]
There are five internally maintained macros which are useful
for writing rules for building targets. The macro $*
stands for the file name 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. The $< macro is only evaluated for
inference rules or the .DEFAULT rule. It is the module
which is out-of-date with respect to the target (that is,
the manufactured dependent file name). Thus, in the rule,
the $< macro would evaluate to the file. Here are two
examples for making optimized files from files:
.c.o: cc -c -O $*.c
.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
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 $?. The reasons for this are debatable.
Special Names [Toc] [Back]
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. Dependents of
this target are not removed when quit or interrupt is hit.
Same effect as the -s option. Same effect as the -i
option. Dependencies of the .SUFFIXES special target are
added to the table of known suffixes.
Suffixes [Toc] [Back]
Certain names (for instance, those ending with have prerequisites
such as can be inferred. If no update commands
for such a file appear in makefile, and if an inferable
prerequisite exists, that prerequisite is compiled to make
the target. In this case, make has inference rules that
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~ .sh .sh~ .c.o .c~.o .c~.c .s.o .s~.o .y.o .y~.o
.l.o .l~.o .y.c .y~.c .l.c .c.a .c~.a .s~.a .h~.h
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
make in a form suitable for recompilation, the following
command is used from /bin/sh: make -fp - 2>/dev/null
The only peculiarity in this output is the (null) string
which printf(3) prints when handed a null string.
A tilde in the above rules refers to an SCCS file. Thus,
the rule 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 the make suffix point-ofview.
Hence, the tilde is a way of changing any file reference
into an SCCS file reference.
A rule with only one suffix (that is, 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 (for example, 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 .y .l .s
Here again, the above command for printing the internal
rules 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 [Toc] [Back]
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 flags 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 from a file with suffix
is specified as an entry with as the target and no dependents.
Shell commands associated with the target define
the rule for making a file from a 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 [Toc] [Back]
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 which 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 where the XX is the
suffix 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, it is assumed that 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 $(CFLAGS1) $<
ar rv $@ $*.o
rm -f $*.o
In fact, the 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
lib: lib(file1.o) lib(file2.o) lib(file3.o)
$(CC) -c $(CFLAGS) $(?:.o=.c)
ar rv lib $?
@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
file names (inside lib) whose C source files are out-ofdate.
The substitution mode translates the to one cannot
transform to of the 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.
Some commands return non-zero status inappropriately. Use
-i to overcome the difficulty. File names with the characters
=, :, or @ do 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.
cc(1), cd(1), lex(1), make(1), make(1p), sh(1), yacc(1)
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