MAKE(1)

NAME
make - maintain program dependencies

SYNOPSIS
make [-BeiknpqrSst] [-C directory] [-D variable] [-d flags] [-f mk] [-I directory] [-j max_processes] [-m directory] [-V variable] [NAME=value] [target ...]

DESCRIPTION
make is a program designed to simplify the maintenance of other programs. Its input is a makefile: a list of specifications (target rules) describing build relationships between programs and other files. By default, the file makefile is used; if no such file is found, it tries Makefile. If neither of these exist, make can still rely on a set of built-in system rules.

If the file ‘.depend’ exists, it will also be read after the main makefile (see mkdep(1)).

The handling of ‘.depend’ is a BSD extension.

Standard options are as follows:

-e  Environment variables override macro assignments within makefiles.

-f mk
    Read file mk instead of the default makefile. If mk is ‘-’, standard input is used. Multiple makefiles may be specified, and are read in the order specified.

-i  Ignore non-zero exit of shell commands in the makefile. Equivalent to specifying ‘-’ before each command line in the makefile.

-k  Continue processing after errors are encountered, but only on those targets that do not depend on the target whose creation caused the error.

-n  Display the commands that would have been executed, but do not actually execute them.

-p  Print a dump of the target rules and variables on stdout. Do not build anything.

-q  Do not execute any commands, but exit with status 0 if the specified targets are up-to-date, and 1 otherwise.

-r  Do not use the built-in rules specified in the system makefile, <sys.mk>.

-S  Stop processing when an error is encountered. This is the default behavior. This is needed to negate the -k option during recursive builds.

-s  Do not echo commands as they are executed. Equivalent to specifying ‘@’ before each command line in the makefile.

-t  Rather than re-building a target as specified in the makefile, create it or update its modification time to make it appear up-to-date, a bit like touch(1).

NAME=value
    Set the value of the variable NAME to value.

Extended options are as follows:

-B  Try to be backwards compatible by executing the commands to make the prerequisites in a target rule in sequence. This is the default, in the absence of -j max_processes.

-C directory
    Enter directory before doing anything.

-D variable
    Define variable to be 1.

-d flags
    Turn on debugging, and specify which portions of make are to print debugging information. flags is one or more of the following:

    A   Print all possible debugging information; equivalent to specifying all of the debugging flags.

    a   Print debugging information about archive searching and caching.

    c   Print debugging information about conditional evaluation.

    d   Print debugging information about directory searching and caching.

    D   Print warning messages about multiply defined command lists.

    e   Print debugging information about expensive command heuristics.

    f   Print debugging information about the expansion of for loops.

    g1  Print the input graph before making anything.

    g2  Print the input graph after making everything, or before exiting on error.

    h   Print information about jobs being held back because of sibling/target groups races.

    j   Print debugging information about forking processes to run commands.

    k   Print debugging information about manually killing processes.

    l   Print commands in Makefile targets regardless of whether or not they are prefixed by @. Also known as loud behavior.

    m   Print debugging information about making targets, including modification dates.

    n   Print debugging information about target names equivalence computations.

    p   Help finding concurrency issues for parallel make by adding some randomization. If RANDOM_ORDER is defined, targets will be shuffled before being built. If RANDOM_DELAY is defined, make will wait between 0 and ${RANDOM_DELAY} seconds before starting a command. A given random seed can be forced by setting RANDOM_SEED, but this does not guarantee reproductibility.

    q   ‘quick death’ option: after a fatal error, instead of waiting for other jobs to die, kill them right away.

    s   Print debugging information about inference (suffix) transformation rules.

    t   Print debugging information about target list maintenance.

    T   Print debugging information about target group determination.

    v   Print debugging information about variable assignment.

-I directory
    Specify a directory in which to search for makefiles and for "..."-style inclusions. Multiple directories can be added to form a search path. Furthermore, the system include path (see the -m option) will be used after this search path.

-j max_processes
    Specify the maximum number of processes that make may have running at any one time.

-m directory
    Specify a directory in which to search for system include files: sys.mk and <...>-style inclusions. Multiple directories can be added to form the system search path. Using -m will override the default system include directory /usr/share/mk.

-V variable
    Print make's idea of the value of variable. Do not build any targets. Multiple instances of this option may be specified; the variables will be printed one per line, with a blank line for each null or undefined variable.

There are seven different types of lines in a makefile: dependency lines, shell commands, variable assignments, include statements, conditional directives, for loops, and comments. Of these, include statements, conditional directives and for loops are extensions.

A complete target rule is composed of a dependency line, followed by a list of shell commands.

In general, lines may be continued from one line to the next by ending them with a backslash (‘\’). The trailing newline character and initial whitespace on the following line are compressed into a single space.

DEPENDENCY LINES
Dependency lines consist of one or more targets, an operator, and zero or more prerequisites:

target ...:[prerequisite ...]

This creates a relationship where the targets “depend” on the prerequisites and are usually built from them. The exact relationship between targets and prerequisites is determined by the operator that separates them.

It is an error to use different dependency operators for the same target.

The operators are as follows:

:   A target is considered out-of-date if any of its prerequisites has been modified more recently than the target (that is, its modification time is less than that of any of its prerequisites). Thus, targets with no prerequisites are always out-of-date.

    make will then execute the list of shell commands associated with that target.

    Additional prerequisites may be specified over additional dependency lines: make will consider all prerequisites for determining out-of-date status. The target is removed if make is interrupted.

!   make first examines all prerequisites and re-creates them as necessary.

    It will then always execute the list of shell commands associated with that target (as if the target always was out-of-date).

    Like:, additional prerequisites may be specified over additional dependency lines, and the target is still removed if make is interrupted.

::  Each dependency line for a target is considered independently. A target is considered out-of-date for this target rule if any of its prerequisites in this dependency has been modified more recently than the target.

    make will then execute the list of shell commands associated with that target. Target rules that specify no prerequisites are always executed.

    The target will not be removed if make is interrupted.

The: operator is the only standard operator. The:: operator is a fairly standard extension, popularized by imake. The! operator is a BSD extension.

As an extension, targets and prerequisites may contain the shell wildcard expressions ‘’?, ‘*’, ‘[]’ and ‘{}’. The expressions ‘’?, ‘*’ and ‘[]’ may only be used as part of the final component of the target or prerequisite, and must be used to describe existing files. The expression ‘{}’ need not necessarily be used to describe existing files. Expansion is in directory order, not alphabetically as done in the shell.

For maximum portability, target names should only consist of periods, underscores, digits and alphabetic characters.

The use of several targets can be a shorthand for duplicate rules. Specifically,

    target1 target2: reqa reqa
    	cmd1
    	cmd2

may be replaced with

    target1: reqa reqa
    	cmd1
    	cmd2
    target2: reqa reqa
    	cmd1
    	cmd2

in general. But make is aware of parallel issues, and will not build those targets concurrently, if not appropriate.

SHELL COMMANDS
Each target may have associated with it a series of shell commands, normally used to build the target. While several dependency lines may name the same target, only one of these dependency lines should be followed by shell commands, and thus define a complete target rule (unless the ‘::’ operator is used). Each of the shell commands in the target rule must be preceded by a tab.

If a command line begins with a combination of the characters, ‘@’, ‘-’ and/or ‘+’, the command is treated specially:

‘@’ causes the command not to be echoed before it is executed.

‘-’ causes any non-zero exit status of the command line to be ignored.

‘+’ causes the command to be executed even if -n has been specified. (This can be useful to debug recursive Makefiles.)

Commands are executed using /bin/sh in "set -e" mode, unless ‘-’ is specified.

As an optimization, make may execute very simple commands without going through an extra shell process, as long as this does not change observable behavior.

INFERENCE RULES
make also maintains a list of valid suffixes through the use of the .SUFFIXES special target.

These suffixes can be used to write generic transformation rules called inference rules.

If a target has the form ‘.s1.s2’, where .s1 and .s2 are currently valid suffixes, then it defines a transformation from *.s1 to *.s2 (double suffix inference). If a target has the form ‘.s1’, where .s1 is a currently valid suffix, then it defines a transformation from *.s1 to * (single suffix inference).

A complete inference rule is a dependency line with such a target, the normal dependency operator, no prerequisites and a list of shell commands.

When make requires a target for which it has no complete target rule, it will try to apply a single active inference rule to create the target.

For instance, with the following Makefile, describing a C program compiled from sources a.c and b.c, with header file a.h:

    .SUFFIXES: .c .o
    .c.o:
    	${CC} ${CFLAGS} -c $<
    prog: a.o b.o
    	${CC} ${CFLAGS} -o $@ a.o
    a.o b.o: a.h
    b.o: b.c
    	${CC} -DFOO ${CFLAGS} -o $@ $<

Consider b.o: there is a complete target rule re-creating it from b.c, so it will be compiled using ${CC} -DFOO.

Consider a.o: there is no explicit target rule, so make will consider valid transforms. Fortunately, there is an inference rule that can create a.o from a.c, so it will be compiled using ${CC}.

Note that extra prerequisites are still taken into account, so both a.o and b.o depend on a.h for re-creation.

Valid suffixes accumulate over .SUFFIXES lines. An empty .SUFFIXES can be used to reset the currently valid list of suffixes, but inference rules already read are still known by make, and they are marked as inactive. Redefining the corresponding suffix (or suffixes) will reactivate the rule.

In case of duplicate inference rules with the same suffix combination, the new rule overrides the old one.

For maximal portability, suffixes should start with a dot.

VARIABLE ASSIGNMENTS
Variables in make are much like variables in the shell and, by tradition, consist of all upper-case letters. They are also called ‘macros’ in various texts. For portability, only periods, underscores, digits and letters should be used for variable names. The five operators that can be used to assign values to variables are as follows:

=   Assign the value to the variable. Any previous value is overridden.

:=  Assign with expansion, i.e., expand the value before assigning it to the variable (extension).

+=  Append the value to the current value of the variable (extension).

?=  Assign the value to the variable if it is not already defined ( BSD extension). Normally, expansion is not done until the variable is referenced.

!=  Expand the value and pass it to the shell for execution and assign the result to the variable. Any newlines in the result are replaced with spaces ( BSD extension).

Any whitespace before the assigned value is removed; if the value is being appended, a single space is inserted between the previous contents of the variable and the appended value.

Several extended assignment operators may be combined together. For instance,

    A ?!= cmd

will only run "cmd" and put its output into A if A is not yet defined.

Variables are expanded by surrounding the variable name with either curly braces (‘{}’) or parentheses (‘()’) and preceding it with a dollar sign (‘$’). If the variable name contains only a single letter, the surrounding braces or parentheses are not required. This shorter form is not recommended.

Variable substitution occurs at two distinct times, depending on where the variable is being used. Variables in dependency lines are expanded as the line is read. Variables in shell commands are expanded when the shell command is executed.

The four different classes of variables (in order of increasing precedence) are:

Environment variables
    Variables defined as part of make's environment.

Global variables
    Variables defined in the makefile or in included makefiles.

Command line variables
    Variables defined as part of the command line.

Local variables
    Variables that are defined specific to a certain target. Standard local variables are as follows:

    @   The name of the target.

    %   The name of the archive member (only valid for library rules).

    !   The name of the archive file (only valid for library rules).

    ?   The list of prerequisites for this target that were deemed out-of-date.

    <   The name of the prerequisite from which this target is to be built, if a valid inference rule (suffix rule) is in scope.

    *   The file prefix of the file, containing only the file portion, no suffix or preceding directory components.

    The six variables ‘@F’, ‘@D’, ‘<F’, ‘<D’, ‘*F’, and ‘*D’ yield the "filename" and "directory" parts of the corresponding macros.

    For maximum compatibility, ‘<’ should only be used for actual inference rules. It is also set for normal target rules when there is an inference rule that matches the current target and prerequisite in scope. That is, in

        .SUFFIXES: .c .o
        file.o: file.c
        	cmd1 $<
        .c.o:
        	cmd2

    building file.o will execute "cmd1 file.c".

    As an extension, make supports the following local variables:

    >   The list of all prerequisites for this target.

    .ALLSRC
        Synonym for ‘>’.

    .ARCHIVE
        Synonym for ‘’!.

    .IMPSRC
        Synonym for ‘<’.

    .MEMBER
        Synonym for ‘%’.

    .OODATE
        Synonym for ‘’?.

    .PREFIX
        Synonym for ‘*’.

    .TARGET
        Synonym for ‘@’.

    These variables may be used on the dependency half of dependency lines, when they make sense.

In addition, make sets or knows about the following internal variables, or environment variables:

$   A single dollar sign ‘$’, i.e., ‘$$’ expands to a single dollar sign.

.MAKE
    The name that make was executed with (argv[0]).

.CURDIR
    A path to the directory where make was executed.

.OBJDIR
    Path to the directory where targets are built. At startup, make searches for an alternate directory to place target files. make tries to chdir(2) into MAKEOBJDIR (or obj if MAKEOBJDIR is not defined), and sets .OBJDIR accordingly. Should that fail, .OBJDIR is set to .CURDIR.

MAKEFILE_LIST
    The list of files read by make.

.MAKEFLAGS
    The environment variable MAKEFLAGS may contain anything that may be specified on make's command line. Its contents are stored in make's .MAKEFLAGS variable. Anything specified on make's command line is appended to the .MAKEFLAGS variable which is then entered into the environment as MAKEFLAGS for all programs which make executes.

MFLAGS
    A shorter synonym for .MAKEFLAGS.

PWD Alternate path to the current directory. make normally sets ‘.CURDIR’ to the canonical path given by getcwd(3). However, if the environment variable PWD is set and gives a path to the current directory, then make sets ‘.CURDIR’ to the value of PWD instead. PWD is always set to the value of ‘.OBJDIR’ for all programs which make executes.

.TARGETS
    List of targets make is currently building.

MACHINE
    Name of the machine architecture make is running on, obtained from the MACHINE environment variable, or through uname(3) if not defined.

MACHINE_ARCH
    Name of the machine architecture make was compiled for, obtained from the MACHINE_ARCH environment variable, or defined at compilation time.

MACHINE_CPU
    Name of the machine processor make was compiled for, obtained from the MACHINE_CPU environment variable, or defined at compilation time. On processors where only one endianness is possible, the value of this variable is always the same as MACHINE_ARCH.

MAKEFILE
    Possibly the file name of the last makefile that has been read. It should not be used; see the BUGS section below.

Variable expansion may be modified to select or modify each word of the variable (where “word” is a whitespace delimited sequence of characters). The general format of a variable expansion is as follows:

    {variable[:modifier[:...]]}

Each modifier begins with a colon and one of the following special characters. The colon may be escaped with a backslash (‘\’).

:E  Replaces each word in the variable with its suffix.

:H  Replaces each word in the variable with everything but the last component.

:L  Replaces each word in the variable with its lower case equivalent.

:U  Replaces each word in the variable with its upper case equivalent.

:Mpattern
    Select only those words that match the rest of the modifier. The standard shell wildcard characters (‘*’, ‘’?, and ‘[]’) may be used. The wildcard characters may be escaped with a backslash (‘\’).

:Npattern
    This is identical to :M, but selects all words which do not match the rest of the modifier.

:Q  Quotes every shell meta-character in the variable, so that it can be passed safely through recursive invocations of make.

:QL Quote list: quotes every shell meta-character in the variable, except whitespace, so that it can be passed to a shell's ‘for’ loops.

:R  Replaces each word in the variable with everything but its suffix.

:S/old_string
    /new_string /[1g] Modify the first occurrence of old_string in the variable's value, replacing it with new_string. If a ‘g’ is appended to the last slash of the pattern, all occurrences in each word are replaced. If a ‘1’ is appended to the last slash of the pattern, only the first word is affected. If old_string begins with a caret (‘^’), old_string is anchored at the beginning of each word. If old_string ends with a dollar sign (‘$’), it is anchored at the end of each word. Inside new_string, an ampersand (‘&’) is replaced by old_string (without any ‘^’ or ‘$’). Any character may be used as a delimiter for the parts of the modifier string. The anchoring, ampersand and delimiter characters may be escaped with a backslash (‘\’).

    Variable expansion occurs in the normal fashion inside both old_string and new_string with the single exception that a backslash is used to prevent the expansion of a dollar sign (‘$’), not a preceding dollar sign as is usual.

:C/pattern
    /replacement /[1g] The:C modifier is just like the:S modifier except that the old and new strings, instead of being simple strings, are an extended regular expression (see re_format(7)) and an ed(1)-style replacement string. Normally, the first occurrence of the pattern in each word of the value is changed. The ‘1’ modifier causes the substitution to apply to at most one word; the ‘g’ modifier causes the substitution to apply to as many instances of the search pattern as occur in the word or words it is found in. Note that ‘1’ and ‘g’ are orthogonal; the former specifies whether multiple words are potentially affected, the latter whether multiple substitutions can potentially occur within each affected word.

:T  Replaces each word in the variable with its last component.

:old_string=new_string
    This is the AT&T UNIX style variable substitution. It must be the last modifier specified. If old_string or new_string do not contain the pattern matching character ‘%’ then it is assumed that they are anchored at the end of each word, so only suffixes or entire words may be replaced. Otherwise ‘%’ is the substring of old_string to be replaced in new_string. The right hand side (new_string) may contain variable values, which will be expanded. To put an actual single dollar, just double it.

All modifiers are BSD extensions, except for the standard AT&T UNIX style variable substitution.

The interpretation of ‘%’ and ‘$’ in AT&T UNIX variable substitutions is not mandated by POSIX, though it is fairly common.

INCLUDE STATEMENTS, CONDITIONALS AND FOR LOOPS
Makefile inclusion, conditional structures and for loops reminiscent of the C programming language are provided in make. All such structures are identified by a line beginning with a single dot (‘’). character. Whitespace characters may follow this dot, e.g.,

    .include <file>

and
    .   include <file>

are identical constructs. Files are included with either ‘.include <file>’ or ‘.include "file"’. Variables between the angle brackets or double quotes are expanded to form the file name. If angle brackets are used, the included makefile is expected to be in the system makefile directory. If double quotes are used, the including makefile's directory and any directories specified using the -I option are searched before the system makefile directory.

Conditional expressions are also preceded by a single dot as the first character of a line. The possible conditionals are as follows:

.undef variable
    Un-define the specified global variable. Only global variables may be un-defined.

.poison variable
    Poison the specified global variable. Any further reference to variable will be flagged as an error.

.poison !defined (variable)
    It is an error to try to use the value of variable in a context where it is not defined.

.poison empty (variable)
    It is an error to try to use the value of variable in a context where it is not defined or empty.

    .if [!]expression [operator expression ...] Test the value of an expression.

    .ifdef [!]variable [operator variable ...] Test the value of a variable.

    .ifndef [!]variable [operator variable ...] Test the value of a variable.

    .ifmake [!]target [operator target ...] Test the target being built.

    .ifnmake [!] target [operator target ...] Test the target being built.

.else
    Reverse the sense of the last conditional.

    .elif [!] expression [operator expression ...] A combination of ‘.else’ followed by ‘.if’.

    .elifdef [!]variable [operator variable ...] A combination of ‘.else’ followed by ‘.ifdef’.

    .elifndef [!]variable [operator variable ...] A combination of ‘.else’ followed by ‘.ifndef’.

    .elifmake [!]target [operator target ...] A combination of ‘.else’ followed by ‘.ifmake’.

    .elifnmake [!]target [operator target ...] A combination of ‘.else’ followed by ‘.ifnmake’.

.endif
    End the body of the conditional.

The operator may be any one of the following:

||  logical OR

&&  Logical AND; of higher precedence than ||.

As in C, make will only evaluate a conditional as far as is necessary to determine its value. Parentheses may be used to change the order of evaluation. The boolean operator ‘’! may be used to logically negate an entire conditional. It is of higher precedence than ‘&&’.

The value of expression may be any of the following:

commands
    Takes a target name as an argument and evaluates to true if the target has been defined and has shell commands associated with it.

defined
    Takes a variable name as an argument and evaluates to true if the variable has been defined.

make
    Takes a target name as an argument and evaluates to true if the target was specified as part of make's command line or was declared the default target (either implicitly or explicitly, see .MAIN) before the line containing the conditional.

empty
    Takes a variable, with possible modifiers, and evaluates to true if the expansion of the variable would result in an empty string.

exists
    Takes a file name as an argument and evaluates to true if the file exists. The file is searched for on the system search path (see .PATH).

target
    Takes a target name as an argument and evaluates to true if the target has been defined.

expression may also be an arithmetic or string comparison. Variable expansion is performed on both sides of the comparison, after which the integral values are compared. A value is interpreted as hexadecimal if it is preceded by 0x, otherwise it is decimal; octal numbers are not supported. The standard C relational operators are all supported. If after variable expansion, either the left or right hand side of a ‘==’ or ‘!=’ operator is not an integral value, then string comparison is performed between the expanded variables. If no relational operator is given, it is assumed that the expanded variable is being compared against 0.

When make is evaluating one of these conditional expressions, and it encounters a word it doesn't recognize, either the “make” or “defined” expression is applied to it, depending on the form of the conditional. If the form is ‘.ifdef’ or ‘.ifndef’, the “defined” expression is applied. Similarly, if the form is ‘.ifmake’ or ‘.ifnmake’, the “make” expression is applied.

If the conditional evaluates to true the parsing of the makefile continues as before. If it evaluates to false, the following lines are skipped. In both cases this continues until a ‘.else’ or ‘.endif’ is found.

For loops are typically used to apply a set of rules to a list of files. The syntax of a for loop is:

    .for variable [variable ...] in expression
    	<make-rules>
    .endfor

After the for expression is evaluated, it is split into words. On each iteration of the loop, one word is assigned to each variable, in order, and these variables are substituted in the make-rules inside the body of the for loop. The number of words must match the number of iteration variables; that is, if there are three iteration variables, the number of words must be a multiple of three.

Loops and conditional expressions may nest arbitrarily, but they may not cross include file boundaries.

make also supports sinclude and -include for compatibility with other implementations. Both use the same syntax:

    sinclude file
    -include file

( note no quotes around file) and will include file, but without any error if it does not exist.

COMMENTS
Comments begin with a hash (‘#’) character, anywhere but in a shell command line, and continue to the end of the line (but a (‘#’) character in a shell command line will be interpreted as a comment by the shell).

TARGET ATTRIBUTES
Some targets may be tagged with some specific attributes by one of the SPECIAL TARGETS or SPECIAL PREREQUISITES described below.

“Always build”
    Run the commands associated with this target even if the -n or -t options were specified. Can be used to mark recursive make's, but prefer standard ‘+cmd’.

“Cheap”
    In parallel mode, don't scan the commands for occurrences of make, thus letting normal recursive -j behavior apply.

“Expensive”
    In parallel mode, assume commands will invoke recursive commands. Once make starts building an expensive target, it won't start building anything else until that target has finished building.

“Ignoring errors”
    Ignore any errors generating by running shell commands, exactly as if they were all preceded by a dash (‘-’).

“Phony”
    A phony target is a target that does not correspond to any object in the file system (more like a placeholder for a list of commands).

    Phony targets are always out-of-date at the start of a run, but make still keeps track of when they are built (that is, when the associated command list finishes running).

“Precious”
    Don't remove the target if make is interrupted in the middle of building it.

“Silent”
    Do not display shell commands before running them, exactly as if they were all preceded by a ‘@’.

SPECIAL TARGETS
make recognizes standard special targets:

.DEFAULT
    If there is a .DEFAULT target rule, with commands but no prequisites, and make can't figure out another way to build a target, it will use that list of commands, setting < and @ appropriately.

.IGNORE
    Mark its prerequisites as “Ignoring errors”.

    If the list of prerequisites is empty, apply that to all targets, exactly like the -i command-line option.

.PRECIOUS
    Mark its prerequisites as “Precious”.

    If the list of prerequisites is empty, apply that to all targets.

.SILENT
    Mark its prerequisites as “Silent”.

    If the list of prerequisites is empty, apply that to all targets, exactly like the -s command-line option.

.SUFFIXES
    See INFERENCE RULES.

and also some other special targets as an extension:

.BEGIN
    Command lines attached to this target are executed before anything else is done.

.CHEAP
    Mark its prerequisites as “Cheap”.

.END
    Command lines attached to this target are executed at the end of a successful run.

.EXPENSIVE
    Mark its prerequisites as “Expensive”.

.INTERRUPT
    Command lines attached to this target are executed if make is interrupted by a SIGINT.

.MADE
    Mark its prerequisites as being up-to-date.

.MAKE
    Mark its prerequisites as “Always build”. Prefer standard ‘+cmd’.

.MAIN
    If no target is specified when make is invoked, this target will be built. This is always set, either explicitly, or implicitly when make selects the default target, to give the user a way to refer to the default target on the command line.

.MAKEFLAGS
    This target provides a way to specify flags for make when the makefile is used. The flags are as if typed to the shell, though the -f option will have no effect.

.NOTPARALLEL
    Disable parallel mode for the current makefile. The -j option is still passed to submakes.

.NO_PARALLEL
    Same as above, for compatibility with other pmake variants.

.ORDER
    The list of prerequisites should be built in sequence.

.PATH
    The prerequisites define a search path: directories that will be searched for files not found in the current directory. If no prerequisites are specified, any previously specified directories are deleted.

.PATH.suffix
    This target is only valid if .suffix is a currently valid suffix. The prerequisites defines a search path for files ending in that suffix. For files not found in the current directory, make will first look in that path, before reverting to the default search path.

.PHONY
    Mark its prerequisites as “Phony” targets.

It is an error to use several special targets, or a special target and normal targets, in a single dependency line.

SPECIAL PREREQUISITES
Of the special targets described in the previous section, the ones that tag prerequisites can also be used as prerequisites, in which case the corresponding targets will be tagged accordingly.

This is an extension, even for standard special targets.

make also recognizes some other prerequisites:

.NOTMAIN
    Normally make selects the first target it encounters as the default target to be built if no target was specified. This prerequisite prevents this target from being selected.

.OPTIONAL
    If a target is marked with this attribute and make can't figure out how to create it, it will ignore this fact and assume the file isn't needed or already exists.

.USE
    Turn the target into make's version of a macro. When the target is used as a prerequisite for another target, the other target acquires the commands, prerequisites, and attributes (except for .USE) of the prerequisite. If the target already has commands, the .USE target's commands are appended to them.

.WAIT
    If .WAIT appears in a dependency line, the prerequisites that precede it are made before the prerequisites that follow it in the line. Loops are not detected and targets that form loops will be silently ignored.

ENVIRONMENT
make uses the following environment variables, if they exist: MACHINE, MACHINE_ARCH, MACHINE_CPU, MAKEFLAGS, MAKEOBJDIR, MAKEOBJDIRPREFIX, and PWD. make also ignores and unsets CDPATH.

FILES
.depend
    list of dependencies
makefile
    default makefile
Makefile
    default makefile if makefile does not exist
sys.mk
    system makefile
/usr/share/mk
    system makefile directory
/usr/obj
    default MAKEOBJDIRPREFIX directory

EXIT STATUS
If -q was specified, the make utility exits with one of the following values:

0   Normal behavior.
1   The target was not up-to date.
>1  An error occurred.

Otherwise, the make utility exits with a value of 0 on success, and >0 if an error occurred.

SEE ALSO
ed(1), mkdep(1), sh(1), getcwd(3), uname(3), re_format(7)

STANDARDS
The make utility is mostly compliant with the p1003.1-2008 specification, though its presence is optional.

The flags [-BCDdIjmV] are extensions to that specification.

Older versions of make used MAKE instead of MAKEFLAGS. This was removed for POSIX compatibility. The internal variable MAKE is set to the same value as .MAKE. Support for this may be removed in the future.

Most of the more esoteric features of make should probably be avoided for greater compatibility.

HISTORY
A make command appeared in AT&T UNIX.

This implementation is a distant derivative of pmake, originally written by Adam de Boor.

BUGS
If the same target is specified several times in complete target rules, make silently ignores all commands after the first non empty set of commands, e.g., in

    a:
    	@echo "Executed"
    a:
    	@echo "Bad luck"

@echo "Bad luck" will be ignored.

.TARGETS is not set to the default target when make is invoked without a target name and no MAIN special target exists.

The evaluation of expression in a test is somewhat simplistic. Variables don't need to be quoted, but strings do: Tests like ‘.if ${VAR} == string’, ‘.if ${VAR} >= 5’, ‘.if 5 <= 10’, and ‘.if string == ${VAR}’ do work, but ‘.if string = ${VAR}’ doesn't.

For loops are expanded before tests, so a fragment such as:

    .for TMACHINE in ${SHARED_ARCHS}
    .if "${TMACHINE}" == ${MACHINE}
         ...
    .endif
    .endfor

requires the quotes.

When handling pre-4.4BSD archives, make may erroneously mark archive members as out of date if the archive name was truncated.

The handling of ‘’; and other special characters in tests may be utterly bogus. For instance, in

    A=abcd;c.c
    .if ${A:R} == "abcd;c"

the test will never match, even though the value is correct.

In a .for loop, only the variable value is used; assignments will be evaluated later, e.g., in

    .for I in a b c d
    I:=${I:S/a/z/}
    A+=$I
    .endfor

‘A’ will evaluate to a b c d after the loop, not z b c d.

ORDER is currently only used in parallel mode, so keep prerequisites ordered for sequential mode!

Distinct target names are treated separately, even though they might correspond to the same file in the file system. This can cause excessive rebuilds of some targets, and bogus races in parallel mode. This can also prevent make from finding a rule to solve a dependency if the target name is not exactly the same as the dependency.

In parallel mode, -j n only limits the number of direct children of make. During recursive invocations, each level may multiply the total number of processes by n. However, make includes some heuristics to try to prevent catastrophic behavior: if a command is marked as expensive, or preceded by ‘+’, or seems to invoke a program that looks sufficiently like ‘make’, make will assume recursive invocation, and not start any new process until said command has finished running. Thus the number of processes run directly or indirectly by make will increase linearly with each level of recursion instead of exponentially.

The MAKEFILE variable cannot be used reliably. It is a compatibility feature and may get set to the last makefile specified, as it is set by System V make.