MAKE(P) POSIX Programmer's Manual MAKE(P)NAMEmake - maintain, update, and regenerate groups of programs (DEVELOP‐
MENT)
SYNOPSISmake [-einpqrst][-f makefile]...[ -k| -S][macro=value]...
[target_name...]
DESCRIPTION
The make utility shall update files that are derived from other files.
A typical case is one where object files are derived from the corre‐
sponding source files. The make utility examines time relationships and
shall update those derived files (called targets) that have modified
times earlier than the modified times of the files (called prerequi‐
sites) from which they are derived. A description file (makefile) con‐
tains a description of the relationships between files, and the com‐
mands that need to be executed to update the targets to reflect changes
in their prerequisites. Each specification, or rule, shall consist of
a target, optional prerequisites, and optional commands to be executed
when a prerequisite is newer than the target. There are two types of
rule:
1. Inference rules, which have one target name with at least one
period ( '.' ) and no slash ( '/' )
2. Target rules, which can have more than one target name
In addition, make shall have a collection of built-in macros and infer‐
ence rules that infer prerequisite relationships to simplify mainte‐
nance of programs.
To receive exactly the behavior described in this section, the user
shall ensure that a portable makefile shall:
* Include the special target .POSIX
* Omit any special target reserved for implementations (a leading
period followed by uppercase letters) that has not been specified by
this section
The behavior of make is unspecified if either or both of these condi‐
tions are not met.
OPTIONS
The make utility shall conform to the Base Definitions volume of
IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.
The following options shall be supported:
-e Cause environment variables, including those with null values,
to override macro assignments within makefiles.
-f makefile
Specify a different makefile. The argument makefile is a path‐
name of a description file, which is also referred to as the
makefile. A pathname of '-' shall denote the standard input.
There can be multiple instances of this option, and they shall
be processed in the order specified. The effect of specifying
the same option-argument more than once is unspecified.
-i Ignore error codes returned by invoked commands. This mode is
the same as if the special target .IGNORE were specified without
prerequisites.
-k Continue to update other targets that do not depend on the cur‐
rent target if a non-ignored error occurs while executing the
commands to bring a target up-to-date.
-n Write commands that would be executed on standard output, but do
not execute them. However, lines with a plus sign ( '+' ) prefix
shall be executed. In this mode, lines with an at sign ( '@' )
character prefix shall be written to standard output.
-p Write to standard output the complete set of macro definitions
and target descriptions. The output format is unspecified.
-q Return a zero exit value if the target file is up-to-date; oth‐
erwise, return an exit value of 1. Targets shall not be updated
if this option is specified. However, a makefile command line
(associated with the targets) with a plus sign ( '+' ) prefix
shall be executed.
-r Clear the suffix list and do not use the built-in rules.
-S Terminate make if an error occurs while executing the commands
to bring a target up-to-date. This shall be the default and the
opposite of -k.
-s Do not write makefile command lines or touch messages (see -t)
to standard output before executing. This mode shall be the same
as if the special target .SILENT were specified without prereq‐
uisites.
-t Update the modification time of each target as though a touch
target had been executed. Targets that have prerequisites but no
commands (see Target Rules ), or that are already up-to-date,
shall not be touched in this manner. Write messages to standard
output for each target file indicating the name of the file and
that it was touched. Normally, the makefile command lines asso‐
ciated with each target are not executed. However, a command
line with a plus sign ( '+' ) prefix shall be executed.
Any options specified in the MAKEFLAGS environment variable shall be
evaluated before any options specified on the make utility command
line. If the -k and -S options are both specified on the make utility
command line or by the MAKEFLAGS environment variable, the last option
specified shall take precedence. If the -f or -p options appear in the
MAKEFLAGS environment variable, the result is undefined.
OPERANDS
The following operands shall be supported:
target_name
Target names, as defined in the EXTENDED DESCRIPTION section. If
no target is specified, while make is processing the makefiles,
the first target that make encounters that is not a special tar‐
get or an inference rule shall be used.
macro=value
Macro definitions, as defined in Macros .
If the target_name and macro= value operands are intermixed on the make
utility command line, the results are unspecified.
STDIN
The standard input shall be used only if the makefile option-argument
is '-' . See the INPUT FILES section.
INPUT FILES
The input file, otherwise known as the makefile, is a text file con‐
taining rules, macro definitions, and comments. See the EXTENDED
DESCRIPTION section.
ENVIRONMENT VARIABLES
The following environment variables shall affect the execution of make:
LANG Provide a default value for the internationalization variables
that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization Vari‐
ables for the precedence of internationalization variables used
to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all
the other internationalization variables.
LC_CTYPE
Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as
opposed to multi-byte characters in arguments and input files).
LC_MESSAGES
Determine the locale that should be used to affect the format
and contents of diagnostic messages written to standard error.
MAKEFLAGS
This variable shall be interpreted as a character string repre‐
senting a series of option characters to be used as the default
options. The implementation shall accept both of the following
formats (but need not accept them when intermixed):
* The characters are option letters without the leading hyphens
or <blank> separation used on a make utility command line.
* The characters are formatted in a manner similar to a portion
of the make utility command line: options are preceded by
hyphens and <blank>-separated as described in the Base Defi‐
nitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility
Syntax Guidelines. The macro= value macro definition oper‐
ands can also be included. The difference between the con‐
tents of MAKEFLAGS and the make utility command line is that
the contents of the variable shall not be subjected to the
word expansions (see Word Expansions ) associated with pars‐
ing the command line values.
NLSPATH
Determine the location of message catalogs for the processing of
LC_MESSAGES .
PROJECTDIR
Provide a directory to be used to search for SCCS files not
found in the current directory. In all of the following cases,
the search for SCCS files is made in the directory SCCS in the
identified directory. If the value of PROJECTDIR begins with a
slash, it shall be considered an absolute pathname; otherwise,
the value of PROJECTDIR is treated as a user name and that
user's initial working directory shall be examined for a subdi‐
rectory src or source. If such a directory is found, it shall be
used. Otherwise, the value is used as a relative pathname.
If PROJECTDIR is not set or has a null value, the search for SCCS files
shall be made in the directory SCCS in the current directory.
The setting of PROJECTDIR affects all files listed in the remainder of
this utility description for files with a component named SCCS.
The value of the SHELL environment variable shall not be used as a
macro and shall not be modified by defining the SHELL macro in a make‐
file or on the command line. All other environment variables, including
those with null values, shall be used as macros, as defined in Macros .
ASYNCHRONOUS EVENTS
If not already ignored, make shall trap SIGHUP, SIGTERM, SIGINT, and
SIGQUIT and remove the current target unless the target is a directory
or the target is a prerequisite of the special target .PRECIOUS or
unless one of the -n, -p, or -q options was specified. Any targets
removed in this manner shall be reported in diagnostic messages of
unspecified format, written to standard error. After this cleanup
process, if any, make shall take the standard action for all other sig‐
nals.
STDOUT
The make utility shall write all commands to be executed to standard
output unless the -s option was specified, the command is prefixed with
an at sign, or the special target .SILENT has either the current target
as a prerequisite or has no prerequisites. If make is invoked without
any work needing to be done, it shall write a message to standard out‐
put indicating that no action was taken. If the -t option is present
and a file is touched, make shall write to standard output a message of
unspecified format indicating that the file was touched, including the
filename of the file.
STDERR
The standard error shall be used only for diagnostic messages.
OUTPUT FILES
Files can be created when the -t option is present. Additional files
can also be created by the utilities invoked by make.
EXTENDED DESCRIPTION
The make utility attempts to perform the actions required to ensure
that the specified targets are up-to-date. A target is considered out-
of-date if it is older than any of its prerequisites or if it does not
exist. The make utility shall treat all prerequisites as targets them‐
selves and recursively ensure that they are up-to-date, processing them
in the order in which they appear in the rule. The make utility shall
use the modification times of files to determine whether the corre‐
sponding targets are out-of-date.
After make has ensured that all of the prerequisites of a target are
up-to-date and if the target is out-of-date, the commands associated
with the target entry shall be executed. If there are no commands
listed for the target, the target shall be treated as up-to-date.
Makefile Syntax
A makefile can contain rules, macro definitions (see Macros ), and com‐
ments. There are two kinds of rules: inference rules and target rules.
The make utility shall contain a set of built-in inference rules. If
the -r option is present, the built-in rules shall not be used and the
suffix list shall be cleared. Additional rules of both types can be
specified in a makefile. If a rule is defined more than once, the value
of the rule shall be that of the last one specified. Macros can also be
defined more than once, and the value of the macro is specified in
Macros . Comments start with a number sign ( '#' ) and continue until
an unescaped <newline> is reached.
By default, the following files shall be tried in sequence: ./makefile
and ./Makefile. If neither ./makefile or ./Makefile are found, other
implementation-defined files may also be tried. On XSI-conformant
systems, the additional files ./s.makefile, SCCS/s.makefile, ./s.Make‐
file, and SCCS/s.Makefile shall also be tried.
The -f option shall direct make to ignore any of these default files
and use the specified argument as a makefile instead. If the '-' argu‐
ment is specified, standard input shall be used.
The term makefile is used to refer to any rules provided by the user,
whether in ./makefile or its variants, or specified by the -f option.
The rules in makefiles shall consist of the following types of lines:
target rules, including special targets (see Target Rules ), inference
rules (see Inference Rules ), macro definitions (see Macros ), empty
lines, and comments.
When an escaped <newline> (one preceded by a backslash) is found any‐
where in the makefile except in a command line, it shall be replaced,
along with any leading white space on the following line, with a single
<space>. When an escaped <newline> is found in a command line in a
makefile, the command line shall contain the backslash, the <newline>,
and the next line, except that the first character of the next line
shall not be included if it is a <tab>.
Makefile Execution
Makefile command lines shall be processed one at a time by writing the
makefile command line to the standard output (unless one of the condi‐
tions listed under '@' suppresses the writing) and executing the com‐
mand(s) in the line. A <tab> may precede the command to standard out‐
put. Command execution shall be as if the makefile command line were
the argument to the system() function. The environment for the command
being executed shall contain all of the variables in the environment of
make.
By default, when make receives a non-zero status from the execution of
a command, it shall terminate with an error message to standard error.
Makefile command lines can have one or more of the following prefixes:
a hyphen ( '-' ), an at sign ( '@' ), or a plus sign ( '+' ). These
shall modify the way in which make processes the command. When a com‐
mand is written to standard output, the prefix shall not be included in
the output.
- If the command prefix contains a hyphen, or the -i option is
present, or the special target .IGNORE has either the current
target as a prerequisite or has no prerequisites, any error
found while executing the command shall be ignored.
@ If the command prefix contains an at sign and the make utility
command line -n option is not specified, or the -s option is
present, or the special target .SILENT has either the current
target as a prerequisite or has no prerequisites, the command
shall not be written to standard output before it is executed.
+ If the command prefix contains a plus sign, this indicates a
makefile command line that shall be executed even if -n, -q, or
-t is specified.
Target Rules
Target rules are formatted as follows:
target [target...]: [prerequisite...][;command]
[<tab>command<tab>command...]
line that does not begin with <tab>
Target entries are specified by a <blank>-separated, non-null list of
targets, then a colon, then a <blank>-separated, possibly empty list of
prerequisites. Text following a semicolon, if any, and all following
lines that begin with a <tab>, are makefile command lines to be exe‐
cuted to update the target. The first non-empty line that does not
begin with a <tab> or '#' shall begin a new entry. An empty or blank
line, or a line beginning with '#' , may begin a new entry.
Applications shall select target names from the set of characters con‐
sisting solely of periods, underscores, digits, and alphabetics from
the portable character set (see the Base Definitions volume of
IEEE Std 1003.1-2001, Section 6.1, Portable Character Set). Implementa‐
tions may allow other characters in target names as extensions. The
interpretation of targets containing the characters '%' and '' is
implementation-defined.
A target that has prerequisites, but does not have any commands, can be
used to add to the prerequisite list for that target. Only one target
rule for any given target can contain commands.
Lines that begin with one of the following are called special targets
and control the operation of make:
.DEFAULT
If the makefile uses this special target, the application shall
ensure that it is specified with commands, but without prerequi‐
sites. The commands shall be used by make if there are no other
rules available to build a target.
.IGNORE
Prerequisites of this special target are targets themselves;
this shall cause errors from commands associated with them to be
ignored in the same manner as specified by the -i option. Subse‐
quent occurrences of .IGNORE shall add to the list of targets
ignoring command errors. If no prerequisites are specified, make
shall behave as if the -i option had been specified and errors
from all commands associated with all targets shall be ignored.
.POSIX The application shall ensure that this special target is speci‐
fied without prerequisites or commands. If it appears as the
first non-comment line in the makefile, make shall process the
makefile as specified by this section; otherwise, the behavior
of make is unspecified.
.PRECIOUS
Prerequisites of this special target shall not be removed if
make receives one of the asynchronous events explicitly
described in the ASYNCHRONOUS EVENTS section. Subsequent occur‐
rences of .PRECIOUS shall add to the list of precious files. If
no prerequisites are specified, all targets in the makefile
shall be treated as if specified with .PRECIOUS.
.SCCS_GET
The application shall ensure that this special target is speci‐
fied without prerequisites. If this special target is included
in a makefile, the commands specified with this target shall
replace the default commands associated with this special target
(see Default Rules ). The commands specified with this target
are used to get all SCCS files that are not found in the current
directory.
When source files are named in a dependency list, make shall treat them
just like any other target. Because the source file is presumed to be
present in the directory, there is no need to add an entry for it to
the makefile. When a target has no dependencies, but is present in the
directory, make shall assume that that file is up-to-date. If, however,
an SCCS file named SCCS/s. source_file is found for a target
source_file, make compares the timestamp of the target file with that
of the SCCS/s.source_file to ensure the target is up-to-date. If the
target is missing, or if the SCCS file is newer, make shall automati‐
cally issue the commands specified for the .SCCS_GET special target to
retrieve the most recent version. However, if the target is writable by
anyone, make shall not retrieve a new version.
.SILENT
Prerequisites of this special target are targets themselves;
this shall cause commands associated with them not to be written
to the standard output before they are executed. Subsequent
occurrences of .SILENT shall add to the list of targets with
silent commands. If no prerequisites are specified, make shall
behave as if the -s option had been specified and no commands or
touch messages associated with any target shall be written to
standard output.
.SUFFIXES
Prerequisites of .SUFFIXES shall be appended to the list of
known suffixes and are used in conjunction with the inference
rules (see Inference Rules ). If .SUFFIXES does not have any
prerequisites, the list of known suffixes shall be cleared.
The special targets .IGNORE, .POSIX, .PRECIOUS, .SILENT, and .SUFFIXES
shall be specified without commands.
Targets with names consisting of a leading period followed by the
uppercase letters "POSIX" and then any other characters are reserved
for future standardization. Targets with names consisting of a leading
period followed by one or more uppercase letters are reserved for
implementation extensions.
Macros
Macro definitions are in the form:
string1 = [string2]
The macro named string1 is defined as having the value of string2,
where string2 is defined as all characters, if any, after the equal
sign, up to a comment character ( '#' ) or an unescaped <newline>. Any
<blank>s immediately before or after the equal sign shall be ignored.
Applications shall select macro names from the set of characters con‐
sisting solely of periods, underscores, digits, and alphabetics from
the portable character set (see the Base Definitions volume of
IEEE Std 1003.1-2001, Section 6.1, Portable Character Set). A macro
name shall not contain an equals sign. Implementations may allow other
characters in macro names as extensions.
Macros can appear anywhere in the makefile. Macro expansions using the
forms $( string1) or ${ string1} shall be replaced by string2, as fol‐
lows:
* Macros in target lines shall be evaluated when the target line is
read.
* Macros in makefile command lines shall be evaluated when the command
is executed.
* Macros in the string before the equals sign in a macro definition
shall be evaluated when the macro assignment is made.
* Macros after the equals sign in a macro definition shall not be
evaluated until the defined macro is used in a rule or command, or
before the equals sign in a macro definition.
The parentheses or braces are optional if string1 is a single charac‐
ter. The macro $$ shall be replaced by the single character '$' . If
string1 in a macro expansion contains a macro expansion, the results
are unspecified.
Macro expansions using the forms $( string1 [: subst1 =[ subst2 ]]) or
${ string1 [: subst1 =[ subst2 ]]} can be used to replace all occur‐
rences of subst1 with subst2 when the macro substitution is performed.
The subst1 to be replaced shall be recognized when it is a suffix at
the end of a word in string1 (where a word, in this context, is defined
to be a string delimited by the beginning of the line, a <blank>, or a
<newline>). If string1 in a macro expansion contains a macro expansion,
the results are unspecified.
Macro expansions in string1 of macro definition lines shall be evalu‐
ated when read. Macro expansions in string2 of macro definition lines
shall be performed when the macro identified by string1 is expanded in
a rule or command.
Macro definitions shall be taken from the following sources, in the
following logical order, before the makefile(s) are read.
1. Macros specified on the make utility command line, in the order
specified on the command line. It is unspecified whether the inter‐
nal macros defined in Internal Macros are accepted from this
source.
2. Macros defined by the MAKEFLAGS environment variable, in the order
specified in the environment variable. It is unspecified whether
the internal macros defined in Internal Macros are accepted from
this source.
3. The contents of the environment, excluding the MAKEFLAGS and SHELL
variables and including the variables with null values.
4. Macros defined in the inference rules built into make.
Macro definitions from these sources shall not override macro defini‐
tions from a lower-numbered source. Macro definitions from a single
source (for example, the make utility command line, the MAKEFLAGS envi‐
ronment variable, or the other environment variables) shall override
previous macro definitions from the same source.
Macros defined in the makefile(s) shall override macro definitions that
occur before them in the makefile(s) and macro definitions from source
4. If the -e option is not specified, macros defined in the makefile(s)
shall override macro definitions from source 3. Macros defined in the
makefile(s) shall not override macro definitions from source 1 or
source 2.
Before the makefile(s) are read, all of the make utility command line
options (except -f and -p) and make utility command line macro defini‐
tions (except any for the MAKEFLAGS macro), not already included in the
MAKEFLAGS macro, shall be added to the MAKEFLAGS macro, quoted in an
implementation-defined manner such that when MAKEFLAGS is read by
another instance of the make command, the original macro's value is
recovered. Other implementation-defined options and macros may also be
added to the MAKEFLAGS macro. If this modifies the value of the MAKE‐
FLAGS macro, or, if the MAKEFLAGS macro is modified at any subsequent
time, the MAKEFLAGS environment variable shall be modified to match the
new value of the MAKEFLAGS macro. The result of setting MAKEFLAGS in
the Makefile is unspecified.
Before the makefile(s) are read, all of the make utility command line
macro definitions (except the MAKEFLAGS macro or the SHELL macro) shall
be added to the environment of make. Other implementation-defined vari‐
ables may also be added to the environment of make.
The SHELL macro shall be treated specially. It shall be provided by
make and set to the pathname of the shell command language interpreter
(see sh ). The SHELL environment variable shall not affect the value of
the SHELL macro. If SHELL is defined in the makefile or is specified on
the command line, it shall replace the original value of the SHELL
macro, but shall not affect the SHELL environment variable. Other
effects of defining SHELL in the makefile or on the command line are
implementation-defined.
Inference Rules
Inference rules are formatted as follows:
target:
<tab>command
[<tab>command]...
line that does not begin with <tab> or #
The application shall ensure that the target portion is a valid target
name (see Target Rules ) of the form .s2 or .s1.s2 (where .s1 and .s2
are suffixes that have been given as prerequisites of the .SUFFIXES
special target and s1 and s2 do not contain any slashes or periods.) If
there is only one period in the target, it is a single-suffix inference
rule. Targets with two periods are double-suffix inference rules.
Inference rules can have only one target before the colon.
The application shall ensure that the makefile does not specify prereq‐
uisites for inference rules; no characters other than white space shall
follow the colon in the first line, except when creating the empty
rule, described below. Prerequisites are inferred, as described below.
Inference rules can be redefined. A target that matches an existing
inference rule shall overwrite the old inference rule. An empty rule
can be created with a command consisting of simply a semicolon (that
is, the rule still exists and is found during inference rule search,
but since it is empty, execution has no effect). The empty rule can
also be formatted as follows:
rule: ;
where zero or more <blank>s separate the colon and semicolon.
The make utility uses the suffixes of targets and their prerequisites
to infer how a target can be made up-to-date. A list of inference rules
defines the commands to be executed. By default, make contains a built-
in set of inference rules. Additional rules can be specified in the
makefile.
The special target .SUFFIXES contains as its prerequisites a list of
suffixes that shall be used by the inference rules. The order in which
the suffixes are specified defines the order in which the inference
rules for the suffixes are used. New suffixes shall be appended to the
current list by specifying a .SUFFIXES special target in the makefile.
A .SUFFIXES target with no prerequisites shall clear the list of suf‐
fixes. An empty .SUFFIXES target followed by a new .SUFFIXES list is
required to change the order of the suffixes.
Normally, the user would provide an inference rule for each suffix.
The inference rule to update a target with a suffix .s1 from a prereq‐
uisite with a suffix .s2 is specified as a target .s2.s1. The internal
macros provide the means to specify general inference rules (see Inter‐
nal Macros ).
When no target rule is found to update a target, the inference rules
shall be checked. The suffix of the target ( .s1) to be built is com‐
pared to the list of suffixes specified by the .SUFFIXES special tar‐
gets. If the .s1 suffix is found in .SUFFIXES, the inference rules
shall be searched in the order defined for the first .s2.s1 rule whose
prerequisite file ( $*.s2) exists. If the target is out-of-date with
respect to this prerequisite, the commands for that inference rule
shall be executed.
If the target to be built does not contain a suffix and there is no
rule for the target, the single suffix inference rules shall be
checked. The single-suffix inference rules define how to build a target
if a file is found with a name that matches the target name with one of
the single suffixes appended. A rule with one suffix .s2 is the defini‐
tion of how to build target from target.s2. The other suffix ( .s1) is
treated as null.
A tilde ( '~' ) in the above rules refers to an SCCS file in the cur‐
rent directory. Thus, the rule .c~.o would transform an SCCS C-language
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 '~' is a way of changing any file reference into an SCCS
file reference.
Libraries
If a target or prerequisite contains parentheses, it shall be treated
as a member of an archive library. For the lib( member .o) expression
lib refers to the name of the archive library and member .o to the mem‐
ber name. The application shall ensure that the member is an object
file with the .o suffix. The modification time of the expression is the
modification time for the member as kept in the archive library; see ar
. The .a suffix shall refer to an archive library. The .s2.a rule shall
be used to update a member in the library from a file with a suffix
.s2.
Internal Macros
The make utility shall maintain five internal macros that can be used
in target and inference rules. In order to clearly define the meaning
of these macros, some clarification of the terms target rule, inference
rule, target, and prerequisite is necessary.
Target rules are specified by the user in a makefile for a particular
target. Inference rules are user-specified or make-specified rules for
a particular class of target name. Explicit prerequisites are those
prerequisites specified in a makefile on target lines. Implicit prereq‐
uisites are those prerequisites that are generated when inference rules
are used. Inference rules are applied to implicit prerequisites or to
explicit prerequisites that do not have target rules defined for them
in the makefile. Target rules are applied to targets specified in the
makefile.
Before any target in the makefile is updated, each of its prerequisites
(both explicit and implicit) shall be updated. This shall be accom‐
plished by recursively processing each prerequisite. Upon recursion,
each prerequisite shall become a target itself. Its prerequisites in
turn shall be processed recursively until a target is found that has no
prerequisites, at which point the recursion stops. The recursion shall
then back up, updating each target as it goes.
In the definitions that follow, the word target refers to one of:
* A target specified in the makefile
* An explicit prerequisite specified in the makefile that becomes the
target when make processes it during recursion
* An implicit prerequisite that becomes a target when make processes
it during recursion
In the definitions that follow, the word prerequisite refers to one of
the following:
* An explicit prerequisite specified in the makefile for a particular
target
* An implicit prerequisite generated as a result of locating an appro‐
priate inference rule and corresponding file that matches the suffix
of the target
The five internal macros are:
$@ The $@ shall evaluate to the full target name of the current
target, or the archive filename part of a library archive tar‐
get. It shall be evaluated for both target and inference rules.
For example, in the .c.a inference rule, $@ represents the out-of-date
.a file to be built. Similarly, in a makefile target rule to build
lib.a from file.c, $@ represents the out-of-date lib.a.
$% The $% macro shall be evaluated only when the current target is
an archive library member of the form libname( member .o). In
these cases, $@ shall evaluate to libname and $% shall evaluate
to member .o. The $% macro shall be evaluated for both target
and inference rules.
For example, in a makefile target rule to build lib.a( file.o), $% rep‐
resents file.o, as opposed to $@, which represents lib.a.
$? The $? macro shall evaluate to the list of prerequisites that
are newer than the current target. It shall be evaluated for
both target and inference rules.
For example, in a makefile target rule to build prog from file1.o,
file2.o, and file3.o, and where prog is not out-of-date with respect to
file1.o, but is out-of-date with respect to file2.o and file3.o, $?
represents file2.o and file3.o.
$< In an inference rule, the $< macro shall evaluate to the file‐
name whose existence allowed the inference rule to be chosen for
the target. In the .DEFAULT rule, the $< macro shall evaluate to
the current target name. The meaning of the $< macro shall be
otherwise unspecified.
For example, in the .c.a inference rule, $< represents the prerequisite
.c file.
$* The $* macro shall evaluate to the current target name with its
suffix deleted. It shall be evaluated at least for inference
rules.
For example, in the .c.a inference rule, $*.o represents the out-of-
date .o file that corresponds to the prerequisite .c file.
Each of the internal macros has an alternative form. When an uppercase
'D' or 'F' is appended to any of the macros, the meaning shall be
changed to the directory part for 'D' and filename part for 'F' . The
directory part is the path prefix of the file without a trailing slash;
for the current directory, the directory part is '.' . When the $?
macro contains more than one prerequisite filename, the $(?D) and $(?F)
(or ${?D} and ${?F}) macros expand to a list of directory name parts
and filename parts respectively.
For the target lib( member .o) and the s2.a rule, the internal macros
shall be defined as:
$< member .s2
$* member
$@ lib
$? member .s2
$% member .o
Default Rules
The default rules for make shall achieve results that are the same as
if the following were used. Implementations that do not support the C-
Language Development Utilities option may omit CC, CFLAGS, YACC,
YFLAGS, LEX, LFLAGS, LDFLAGS, and the .c, .y, and .l inference rules.
Implementations that do not support FORTRAN may omit FC, FFLAGS, and
the .f inference rules. Implementations may provide additional macros
and rules.
SPECIAL TARGETS
.SCCS_GET: sccs $(SCCSFLAGS) get $(SCCSGETFLAGS) $@
.SUFFIXES: .o .c .y .l .a .sh .f .c~ .y~ .l~ .sh~ .f~
MACROS
MAKE=make
AR=ar
ARFLAGS=-rv
YACC=yacc
YFLAGS=
LEX=lex
LFLAGS=
LDFLAGS=
CC=c99
CFLAGS=-O
FC=fort77
FFLAGS=-O 1
GET=get
GFLAGS=
SCCSFLAGS=
SCCSGETFLAGS=-s
SINGLE SUFFIX RULES
.c:
$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $<
.f:
$(FC) $(FFLAGS) $(LDFLAGS) -o $@ $<
.sh:
cp $< $@
chmod a+x $@
.c~:
$(GET) $(GFLAGS) -p $< > $*.c
$(CC) $(CFLAGS) $(LDFLAGS) -o $@ $*.c
.f~:
$(GET) $(GFLAGS) -p $< > $*.f
$(FC) $(FFLAGS) $(LDFLAGS) -o $@ $*.f
.sh~:
$(GET) $(GFLAGS) -p $< > $*.sh
cp $*.sh $@
chmod a+x $@
DOUBLE SUFFIX RULES
.c.o:
$(CC) $(CFLAGS) -c $<
.f.o:
$(FC) $(FFLAGS) -c $<
.y.o:
$(YACC) $(YFLAGS) $<
$(CC) $(CFLAGS) -c y.tab.c
rm -f y.tab.c
mv y.tab.o $@
.l.o:
$(LEX) $(LFLAGS) $<
$(CC) $(CFLAGS) -c lex.yy.c
rm -f lex.yy.c
mv lex.yy.o $@
.y.c:
$(YACC) $(YFLAGS) $<
mv y.tab.c $@
.l.c:
$(LEX) $(LFLAGS) $<
mv lex.yy.c $@
.c~.o:
$(GET) $(GFLAGS) -p $< > $*.c
$(CC) $(CFLAGS) -c $*.c
.f~.o:
$(GET) $(GFLAGS) -p $< > $*.f
$(FC) $(FFLAGS) -c $*.f
.y~.o:
$(GET) $(GFLAGS) -p $< > $*.y
$(YACC) $(YFLAGS) $*.y
$(CC) $(CFLAGS) -c y.tab.c
rm -f y.tab.c
mv y.tab.o $@
.l~.o:
$(GET) $(GFLAGS) -p $< > $*.l
$(LEX) $(LFLAGS) $*.l
$(CC) $(CFLAGS) -c lex.yy.c
rm -f lex.yy.c
mv lex.yy.o $@
.y~.c:
$(GET) $(GFLAGS) -p $< > $*.y
$(YACC) $(YFLAGS) $*.y
mv y.tab.c $@
.l~.c:
$(GET) $(GFLAGS) -p $< > $*.l
$(LEX) $(LFLAGS) $*.l
mv lex.yy.c $@
.c.a:
$(CC) -c $(CFLAGS) $<
$(AR) $(ARFLAGS) $@ $*.o
rm -f $*.o
.f.a:
$(FC) -c $(FFLAGS) $<
$(AR) $(ARFLAGS) $@ $*.o
rm -f $*.o
EXIT STATUS
When the -q option is specified, the make utility shall exit with one
of the following values:
0 Successful completion.
1 The target was not up-to-date.
>1 An error occurred.
When the -q option is not specified, the make utility shall exit with
one of the following values:
0 Successful completion.
>0 An error occurred.
CONSEQUENCES OF ERRORS
Default.
The following sections are informative.
APPLICATION USAGE
If there is a source file (such as ./source.c) and there are two SCCS
files corresponding to it ( ./s.source.c and ./SCCS/s.source.c), on
XSI-conformant systems make uses the SCCS file in the current direc‐
tory. However, users are advised to use the underlying SCCS utilities (
admin, delta, get, and so on) or the sccs utility for all source files
in a given directory. If both forms are used for a given source file,
future developers are very likely to be confused.
It is incumbent upon portable makefiles to specify the .POSIX special
target in order to guarantee that they are not affected by local exten‐
sions.
The -k and -S options are both present so that the relationship between
the command line, the MAKEFLAGS variable, and the makefile can be con‐
trolled precisely. If the k flag is passed in MAKEFLAGS and a command
is of the form:
$(MAKE) -S foo
then the default behavior is restored for the child make.
When the -n option is specified, it is always added to MAKEFLAGS . This
allows a recursive make-n target to be used to see all of the action
that would be taken to update target.
Because of widespread historical practice, interpreting a '#' number
sign inside a variable as the start of a comment has the unfortunate
side effect of making it impossible to place a number sign in a vari‐
able, thus forbidding something like:
CFLAGS = "-D COMMENT_CHAR='#'"
Many historical make utilities stop chaining together inference rules
when an intermediate target is nonexistent. For example, it might be
possible for a make to determine that both .y.c and .c.o could be used
to convert a .y to a .o. Instead, in this case, make requires the use
of a .y.o rule.
The best way to provide portable makefiles is to include all of the
rules needed in the makefile itself. The rules provided use only fea‐
tures provided by other parts of this volume of IEEE Std 1003.1-2001.
The default rules include rules for optional commands in this volume of
IEEE Std 1003.1-2001. Only rules pertaining to commands that are pro‐
vided are needed in an implementation's default set.
Macros used within other macros are evaluated when the new macro is
used rather than when the new macro is defined. Therefore:
MACRO = value1NEW = $(MACRO)
MACRO = value2
target:
echo $(NEW)
would produce value2 and not value1 since NEW was not expanded until it
was needed in the echo command line.
Some historical applications have been known to intermix target_name
and macro=name operands on the command line, expecting that all of the
macros are processed before any of the targets are dealt with. Conform‐
ing applications do not do this, although some backwards-compatibility
support may be included in some implementations.
The following characters in filenames may give trouble: '=' , ':' , '`'
, '" , and '@' . For inference rules, the description of $< and $? seem
similar. However, an example shows the minor difference. In a makefile
containing:
foo.o: foo.h
if foo.h is newer than foo.o, yet foo.c is older than foo.o, the built-
in rule to make foo.o from foo.c is used, with $< equal to foo.c and $?
equal to foo.h. If foo.c is also newer than foo.o, $< is equal to foo.c
and $? is equal to foo.h foo.c.
EXAMPLES
1. The following command:
make
makes the first target found in the makefile.
2. The following command:
make junk
makes the target junk.
3. 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
c99 a.o b.o -o pgm
a.o: incl.h a.c
c99 -c a.c
b.o: incl.h b.c
c99 -c b.c
4. An example for making optimized .o files from .c files is:
.c.o:
c99 -c -O $*.c
or:
.c.o:
c99 -c -O $<
5. The most common use of the archive interface follows. Here, it is
assumed that the source files are all C-language source:
lib: lib(file1.o) lib(file2.o) lib(file3.o)
@echo lib is now up-to-date
The .c.a rule is used to make file1.o, file2.o, and file3.o and insert
them into lib.
The treatment of escaped <newline>s throughout the makefile is histori‐
cal practice. For example, the inference rule:
.c.o\
:
works, and the macro:
f= bar baz\
biz
a:
echo ==$f==
echoes "==bar baz biz==" .
If $? were:
/usr/include/stdio.h /usr/include/unistd.h foo.h
then $(?D) would be:
/usr/include /usr/include .
and $(?F) would be:
stdio.h unistd.h foo.h
6. The contents of the built-in rules can be viewed by running:
make-p -f /dev/null 2>/dev/null
RATIONALE
The make utility described in this volume of IEEE Std 1003.1-2001 is
intended to provide the means for changing portable source code into
executables that can be run on an IEEE Std 1003.1-2001-conforming sys‐
tem. It reflects the most common features present in System V and BSD
makes.
Historically, the make utility has been an especially fertile ground
for vendor and research organization-specific syntax modifications and
extensions. Examples include:
* Syntax supporting parallel execution (such as from various multi-
processor vendors, GNU, and others)
* Additional "operators" separating targets and their prerequisites
(System V, BSD, and others)
* Specifying that command lines containing the strings "${MAKE}" and
"$(MAKE)" are executed when the -n option is specified (GNU and Sys‐
tem V)
* Modifications of the meaning of internal macros when referencing
libraries (BSD and others)
* Using a single instance of the shell for all of the command lines of
the target (BSD and others)
* Allowing spaces as well as tabs to delimit command lines (BSD)
* Adding C preprocessor-style "include" and "ifdef" constructs (System
V, GNU, BSD, and others)
* Remote execution of command lines (Sprite and others)
* Specifying additional special targets (BSD, System V, and most oth‐
ers)
Additionally, many vendors and research organizations have rethought
the basic concepts of make, creating vastly extended, as well as com‐
pletely new, syntaxes. Each of these versions of make fulfills the
needs of a different community of users; it is unreasonable for this
volume of IEEE Std 1003.1-2001 to require behavior that would be incom‐
patible (and probably inferior) to historical practice for such a com‐
munity.
In similar circumstances, when the industry has enough sufficiently
incompatible formats as to make them irreconcilable, this volume of
IEEE Std 1003.1-2001 has followed one or both of two courses of action.
Commands have been renamed ( cksum, echo, and pax) and/or command line
options have been provided to select the desired behavior ( grep, od,
and pax).
Because the syntax specified for the make utility is, by and large, a
subset of the syntaxes accepted by almost all versions of make, it was
decided that it would be counter-productive to change the name. And
since the makefile itself is a basic unit of portability, it would not
be completely effective to reserve a new option letter, such as make-P, to achieve the portable behavior. Therefore, the special target
.POSIX was added to the makefile, allowing users to specify "standard"
behavior. This special target does not preclude extensions in the make
utility, nor does it preclude such extensions being used by the make‐
file specifying the target; it does, however, preclude any extensions
from being applied that could alter the behavior of previously valid
syntax; such extensions must be controlled via command line options or
new special targets. It is incumbent upon portable makefiles to specify
the .POSIX special target in order to guarantee that they are not
affected by local extensions.
The portable version of make described in this reference page is not
intended to be the state-of-the-art software generation tool and, as
such, some newer and more leading-edge features have not been included.
An attempt has been made to describe the portable makefile in a manner
that does not preclude such extensions as long as they do not disturb
the portable behavior described here.
When the -n option is specified, it is always added to MAKEFLAGS . This
allows a recursive make-n target to be used to see all of the action
that would be taken to update target.
The definition of MAKEFLAGS allows both the System V letter string and
the BSD command line formats. The two formats are sufficiently differ‐
ent to allow implementations to support both without ambiguity.
Early proposals stated that an "unquoted" number sign was treated as
the start of a comment. The make utility does not pay any attention to
quotes. A number sign starts a comment regardless of its surroundings.
The text about "other implementation-defined pathnames may also be
tried" in addition to ./makefile and ./Makefile is to allow such exten‐
sions as SCCS/s.Makefile and other variations. It was made an implemen‐
tation-defined requirement (as opposed to unspecified behavior) to
highlight surprising implementations that might select something unex‐
pected like /etc/Makefile. XSI-conformant systems also try ./s.make‐
file, SCCS/s.makefile, ./s.Makefile, and SCCS/s.Makefile.
Early proposals contained the macro NPROC as a means of specifying that
make should use n processes to do the work required. While this feature
is a valuable extension for many systems, it is not common usage and
could require other non-trivial extensions to makefile syntax. This
extension is not required by this volume of IEEE Std 1003.1-2001, but
could be provided as a compatible extension. The macro PARALLEL is used
by some historical systems with essentially the same meaning (but with‐
out using a name that is a common system limit value). It is suggested
that implementors recognize the existing use of NPROC and/or PARALLEL
as extensions to make.
The default rules are based on System V. The default CC= value is c99
instead of cc because this volume of IEEE Std 1003.1-2001 does not
standardize the utility named cc. Thus, every conforming application
would be required to define CC= c99 to expect to run. There is no
advantage conferred by the hope that the makefile might hit the "pre‐
ferred" compiler because this cannot be guaranteed to work. Also, since
the portable makescript can only use the c99 options, no advantage is
conferred in terms of what the script can do. It is a quality-of-imple‐
mentation issue as to whether c99 is as valuable as cc.
The -d option to make is frequently used to produce debugging informa‐
tion, but is too implementation-defined to add to this volume of
IEEE Std 1003.1-2001.
The -p option is not passed in MAKEFLAGS on most historical implementa‐
tions and to change this would cause many implementations to break
without sufficiently increased portability.
Commands that begin with a plus sign ( '+' ) are executed even if the
-n option is present. Based on the GNU version of make, the behavior of
-n when the plus-sign prefix is encountered has been extended to apply
to -q and -t as well. However, the System V convention of forcing com‐
mand execution with -n when the command line of a target contains
either of the strings "$(MAKE)" or "${MAKE}" has not been adopted. This
functionality appeared in early proposals, but the danger of this
approach was pointed out with the following example of a portion of a
makefile:
subdir:
cd subdir; rm all_the_files; $(MAKE)
The loss of the System V behavior in this case is well-balanced by the
safety afforded to other makefiles that were not aware of this situa‐
tion. In any event, the command line plus-sign prefix can provide the
desired functionality.
The double colon in the target rule format is supported in BSD systems
to allow more than one target line containing the same target name to
have commands associated with it. Since this is not functionality
described in the SVID or XPG3 it has been allowed as an extension, but
not mandated.
The default rules are provided with text specifying that the built-in
rules shall be the same as if the listed set were used. The intent is
that implementations should be able to use the rules without change,
but will be allowed to alter them in ways that do not affect the pri‐
mary behavior.
The best way to provide portable makefiles is to include all of the
rules needed in the makefile itself. The rules provided use only fea‐
tures provided by other portions of this volume of
IEEE Std 1003.1-2001. The default rules include rules for optional
commands in this volume of IEEE Std 1003.1-2001. Only rules pertaining
to commands that are provided are needed in the default set of an
implementation.
One point of discussion was whether to drop the default rules list from
this volume of IEEE Std 1003.1-2001. They provide convenience, but do
not enhance portability of applications. The prime benefit is in
portability of users who wish to type make command and have the command
build from a command.c file.
The historical MAKESHELL feature was omitted. In some implementations
it is used to let a user override the shell to be used to run make com‐
mands. This was confusing; for a portable make, the shell should be
chosen by the makefile writer or specified on the make command line and
not by a user running make.
The make utilities in most historical implementations process the pre‐
requisites of a target in left-to-right order, and the makefile format
requires this. It supports the standard idiom used in many makefiles
that produce yacc programs; for example:
foo: y.tab.o lex.o main.o
$(CC) $(CFLAGS) -o $@ t.tab.o lex.o main.o
In this example, if make chose any arbitrary order, the lex.o might not
be made with the correct y.tab.h. Although there may be better ways to
express this relationship, it is widely used historically. Implementa‐
tions that desire to update prerequisites in parallel should require an
explicit extension to make or the makefile format to accomplish it, as
described previously.
The algorithm for determining a new entry for target rules is partially
unspecified. Some historical makes allow blank, empty, or comment lines
within the collection of commands marked by leading <tab>s. A conform‐
ing makefile must ensure that each command starts with a <tab>, but
implementations are free to ignore blank, empty, and comment lines
without triggering the start of a new entry.
The ASYNCHRONOUS EVENTS section includes having SIGTERM and SIGHUP,
along with the more traditional SIGINT and SIGQUIT, remove the current
target unless directed not to do so. SIGTERM and SIGHUP were added to
parallel other utilities that have historically cleaned up their work
as a result of these signals. When make receives any signal other than
SIGQUIT, it is required to resend itself the signal it received so that
it exits with a status that reflects the signal. The results from
SIGQUIT are partially unspecified because, on systems that create core
files upon receipt of SIGQUIT, the core from make would conflict with a
core file from the command that was running when the SIGQUIT arrived.
The main concern was to prevent damaged files from appearing up-to-date
when make is rerun.
The .PRECIOUS special target was extended to affect all targets glob‐
ally (by specifying no prerequisites). The .IGNORE and .SILENT special
targets were extended to allow prerequisites; it was judged to be more
useful in some cases to be able to turn off errors or echoing for a
list of targets than for the entire makefile. These extensions to make
in System V were made to match historical practice from the BSD make.
Macros are not exported to the environment of commands to be run. This
was never the case in any historical make and would have serious conse‐
quences. The environment is the same as the environment to make except
that MAKEFLAGS and macros defined on the make command line are added.
Some implementations do not use system() for all command lines, as
required by the portable makefile format; as a performance enhancement,
they select lines without shell metacharacters for direct execution by
execve(). There is no requirement that system() be used specifically,
but merely that the same results be achieved. The metacharacters typi‐
cally used to bypass the direct execve() execution have been any of:
= | ^ ( ) ; & < > * ? [ ] : $ ` ' " \ \n
The default in some advanced versions of make is to group all the com‐
mand lines for a target and execute them using a single shell invoca‐
tion; the System V method is to pass each line individually to a sepa‐
rate shell. The single-shell method has the advantages in performance
and the lack of a requirement for many continued lines. However, con‐
verting to this newer method has caused portability problems with many
historical makefiles, so the behavior with the POSIX makefile is speci‐
fied to be the same as that of System V. It is suggested that the spe‐
cial target .ONESHELL be used as an implementation extension to achieve
the single-shell grouping for a target or group of targets.
Novice users of make have had difficulty with the historical need to
start commands with a <tab>. Since it is often difficult to discern
differences between <tab>s and <space>s on terminals or printed list‐
ings, confusing bugs can arise. In early proposals, an attempt was made
to correct this problem by allowing leading <blank>s instead of <tab>s.
However, implementors reported many makefiles that failed in subtle
ways following this change, and it is difficult to implement a make
that unambiguously can differentiate between macro and command lines.
There is extensive historical practice of allowing leading spaces
before macro definitions. Forcing macro lines into column 1 would be a
significant backwards-compatibility problem for some makefiles. There‐
fore, historical practice was restored.
The System V INCLUDE feature was considered, but not included. This
would treat a line that began in the first column and contained INCLUDE
<filename> as an indication to read <filename> at that point in the
makefile. This is difficult to use in a portable way, and it raises
concerns about nesting levels and diagnostics. System V, BSD, GNU, and
others have used different methods for including files.
The System V dynamic dependency feature was not included. It would sup‐
port:
cat: $$@.c
that would expand to;
cat: cat.c
This feature exists only in the new version of System V make and, while
useful, is not in wide usage. This means that macros are expanded twice
for prerequisites: once at makefile parse time and once at target
update time.
Consideration was given to adding metarules to the POSIX make. This
would make %.o: %.c the same as .c.o:. This is quite useful and avail‐
able from some vendors, but it would cause too many changes to this
make to support. It would have introduced rule chaining and new substi‐
tution rules. However, the rules for target names have been set to
reserve the '%' and '' characters. These are traditionally used to
implement metarules and quoting of target names, respectively. Imple‐
mentors are strongly encouraged to use these characters only for these
purposes.
A request was made to extend the suffix delimiter character from a
period to any character. The metarules feature in newer makes solves
this problem in a more general way. This volume of IEEE Std 1003.1-2001
is staying with the more conservative historical definition.
The standard output format for the -p option is not described because
it is primarily a debugging option and because the format is not gener‐
ally useful to programs. In historical implementations the output is
not suitable for use in generating makefiles. The -p format has been
variable across historical implementations. Therefore, the definition
of -p was only to provide a consistently named option for obtaining
make script debugging information.
Some historical implementations have not cleared the suffix list with
-r.
Implementations should be aware that some historical applications have
intermixed target_name and macro= value operands on the command line,
expecting that all of the macros are processed before any of the tar‐
gets are dealt with. Conforming applications do not do this, but some
backwards-compatibility support may be warranted.
Empty inference rules are specified with a semicolon command rather
than omitting all commands, as described in an early proposal. The lat‐
ter case has no traditional meaning and is reserved for implementation
extensions, such as in GNU make.
FUTURE DIRECTIONS
None.
SEE ALSO
Shell Command Language , ar , c99 , get , lex , sccs , sh , yacc , the
System Interfaces volume of IEEE Std 1003.1-2001, exec, system()COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 MAKE(P)
