.\"	$OpenBSD: make.1,v 1.134 2021/11/11 20:42:54 jmc Exp $
.\"	$NetBSD: make.1,v 1.18 1997/03/10 21:19:53 christos Exp $
.\"
.\" Copyright (c) 1990, 1993
.\"	The Regents of the University of California.  All rights reserved.
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\"	from: @(#)make.1	8.4 (Berkeley) 3/19/94
.\"
.Dd $Mdocdate: November 11 2021 $
.Dt MAKE 1
.Os
.Sh NAME
.Nm make
.Nd maintain program dependencies
.Sh SYNOPSIS
.Nm make
.Op Fl BeiknpqrSst
.Op Fl C Ar directory
.Op Fl D Ar variable
.Op Fl d Ar flags
.Op Fl f Ar mk
.Op Fl I Ar directory
.Op Fl j Ar max_processes
.Op Fl m Ar directory
.Op Fl V Ar variable
.Op Ar NAME Ns = Ns Ar value
.Bk -words
.Op Ar target ...
.Ek
.Sh DESCRIPTION
.Nm
is a program designed to simplify the maintenance of other programs.
Its input is a
.Em makefile :
a list of specifications (target rules) describing build
relationships between programs and other files.
By default, the file
.Pa makefile
is used;
if no such file is found, it tries
.Pa Makefile .
If neither of these exist,
.Nm
can still rely on a set of built-in system rules.
.Pp
If the file
.Sq Pa .depend
exists, it will also be read after the main
.Ar makefile
(see
.Xr mkdep 1 ) .
.Pp
The handling of
.Sq Pa .depend
is a
.Bx
extension.
.Pp
If a list of
.Ar target ...
is specified,
.Nm
will build those targets.
Otherwise a default target will be built:
either a target explicitly marked with
.Ic .MAIN
or the first target encountered in the
.Em makefile .
.Pp
Standard options are as follows:
.Bl -tag -width Ds
.It Fl e
Environment variables override macro assignments within
makefiles.
.It Fl f Ar mk
Read file
.Ar mk
instead of the default makefile.
If
.Ar mk
is
.Ql \- ,
standard input is used.
Multiple makefiles may be specified, and are read in the order specified.
.It Fl i
Ignore non-zero exit of shell commands in the makefile.
Equivalent to specifying
.Ql \-
before each command line in the makefile.
.It Fl k
Continue processing after errors are encountered, but only on those targets
that do not depend on the target whose creation caused the error.
.It Fl n
Display the commands that would have been executed, but do not actually
execute them.
.It Fl p
Print a dump of the target rules and variables on stdout.
Do not build anything.
.It Fl q
Do not execute any commands, but exit with status 0 if the specified targets
are up to date, and 1 otherwise.
.It Fl r
Do not use the built-in rules specified in the system makefile,
.Pa <sys.mk> .
.It Fl S
Stop processing when an error is encountered.
This is the default behavior.
This is needed to negate the
.Fl k
option during recursive builds.
.It Fl s
Do not echo commands as they are executed.
Equivalent to specifying
.Sq Ic @
before each command line in the makefile.
.It Fl 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
.Xr touch 1 .
.It Ar NAME Ns = Ns Ar value
Set the value of the variable
.Ar NAME
to
.Ar value .
.El
.Pp
Extended options are as follows:
.Bl -tag -width Ds
.It Fl 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
.Fl j Ar max_processes .
.It Fl C Ar directory
Enter
.Ar directory
before doing anything.
.It Fl D Ar variable
Define
.Ar variable
to be 1.
.It Fl d Ar flags
Turn on debugging, and specify which portions of
.Nm
are to print debugging information.
.Ar flags
is one or more of the following:
.Bl -tag -width Ds
.It Ar A
Print all possible debugging information;
equivalent to specifying all of the debugging flags.
.It Ar a
Print debugging information about archive searching and caching.
.It Ar c
Print debugging information about conditional evaluation.
.It Ar d
Print debugging information about directory searching and caching.
.It Ar D
Print warning messages about multiply defined command lists.
.It Ar e
Print debugging information about expensive command heuristics.
.It Ar f
Print debugging information about the expansion of for loops.
.It Ar "g1"
Print the input graph before making anything.
.It Ar "g2"
Print the input graph after making everything, or before exiting
on error.
.It Ar h
Print information about jobs being held back because of sibling/target
groups races.
.It Ar j
Print debugging information about forking processes to run commands.
.It Ar k
Print debugging information about manually killing processes.
.It Ar l
Print commands in Makefile targets regardless of whether or not they are
prefixed by @.
Also known as loud behavior.
.It Ar m
Print debugging information about making targets, including modification
dates.
.It Ar n
Print debugging information about target names equivalence computations.
.It Ar p
Help finding concurrency issues for parallel make by adding some
randomization.
If
.Va RANDOM_ORDER
is defined,
targets will be shuffled before being built.
If
.Va RANDOM_DELAY
is defined,
.Nm
will wait between 0 and ${RANDOM_DELAY} seconds before starting a command.
A given random seed can be forced by setting
.Va RANDOM_SEED ,
but this does not guarantee reproducibility.
.It Ar q
.Sq quick death
option: after a fatal error, instead of waiting for other jobs to die,
kill them right away.
.It Ar s
Print debugging information about inference (suffix) transformation rules.
.It Ar t
Print debugging information about target list maintenance.
.It Ar T
Print debugging information about target group determination.
.It Ar v
Print debugging information about variable assignment.
.El
.It Fl I Ar 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
.Fl m
option) will be used after this search path.
.It Fl j Ar max_processes
Specify the maximum number of processes that
.Nm
may have running at any one time.
.It Fl m Ar directory
Specify a directory in which to search for system include files:
.Pa sys.mk
and <...>-style inclusions.
Multiple directories can be added to form the system search path.
Using
.Fl m
will override the default system include directory
.Pa /usr/share/mk .
.It Fl V Ar variable
Print
.Nm make Ns 's
idea of the value of
.Ar 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.
.El
.Pp
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.
.Pp
A complete target rule is composed of a dependency line,
followed by a list of shell commands.
.Pp
In general, lines may be continued from one line to the next by ending
them with a backslash
.Pq Ql \e .
The trailing newline character and initial whitespace on the following
line are compressed into a single space.
.Sh DEPENDENCY LINES
Dependency lines consist of one or more targets, an operator, and zero
or more prerequisites:
.Bd -ragged -offset indent
.Ar target ... : Ns Op Ar prerequisite ...
.Ed
.Pp
This creates a relationship where the targets
.Dq 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.
.Pp
It is an error to use different dependency operators for the same target.
.Pp
The operators are as follows:
.Bl -tag -width flag
.It Ic \&:
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.
.Pp
.Nm
will then execute the list of shell commands associated with that target.
.Pp
Additional prerequisites may be specified over additional dependency lines:
.Nm
will consider all prerequisites for determining out-of-date status.
The target is removed if
.Nm
is interrupted.
.It Ic \&!
.Nm
first examines all prerequisites and re-creates them as necessary.
.Pp
It will then always execute the list of shell commands associated with
that target (as if the target always was out of date).
.Pp
Like
.Ic \&: ,
additional prerequisites may be specified over additional dependency lines,
and the target is still removed if
.Nm
is interrupted.
.It Ic \&::
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.
.Pp
.Nm
will then execute the list of shell commands associated with that target.
Target rules that specify no prerequisites are always executed.
.Pp
The target will not be removed if
.Nm
is interrupted.
.El
.Pp
The
.Ic \&:
operator is the only standard operator.
The
.Ic \&::
operator is a fairly standard extension,
popularized by
.Sy imake .
The
.Ic !\&
operator is a
.Bx
extension.
.Pp
As an extension, targets and prerequisites may contain the shell wildcard
expressions
.Ql \&? ,
.Ql * ,
.Ql []
and
.Ql {} .
The expressions
.Ql \&? ,
.Ql *
and
.Ql []
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
.Ql {}
need not necessarily be used to describe existing files.
Expansion is in directory order, not alphabetically as done in the shell.
.Pp
For maximum portability, target names should only consist of periods,
underscores, digits and alphabetic characters.
.Pp
The use of several targets can be a shorthand for duplicate rules.
Specifically,
.Bd -literal -offset indent
target1 target2: reqa reqa
	cmd1
	cmd2
.Ed
.Pp
may be replaced with
.Bd -literal -offset indent
target1: reqa reqa
	cmd1
	cmd2
target2: reqa reqa
	cmd1
	cmd2
.Ed
.Pp
in general.
But
.Nm
is aware of parallel issues, and will not build those targets concurrently,
if not appropriate.
.Sh 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
.Sq Ic ::
operator is used).
Each of the shell commands in the target rule
.Em must
be preceded by a tab.
.Pp
If a command line begins with a combination of the characters,
.Sq Ic @ ,
.Sq Ic \-
and/or
.Sq Ic + ,
the command is treated specially:
.Bl -tag -width `@'
.It Sq Ic @
causes the command not to be echoed before it is executed.
.It Sq Ic \-
causes any non-zero exit status of the command line to be ignored.
.It Sq Ic +
causes the command to be executed even if
.Fl n
has been specified.
(This can be useful to debug recursive Makefiles.)
.El
.Pp
Commands are executed using
.Pa /bin/sh
in
.Qq set -e
mode, unless
.Sq Ic \-
is specified.
.Pp
As an optimization,
.Nm
may execute very simple commands without going through an extra shell
process, as long as this does not change observable behavior.
.Sh INFERENCE RULES
.Nm
also maintains a list of valid suffixes through the use of the
.Ic .SUFFIXES
special target.
.Pp
These suffixes can be used to write generic transformation rules called
inference rules.
.Pp
If a target has the form
.Sq \&.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
.Sq \&.s1 ,
where .s1 is a currently valid suffix, then it defines a
transformation from *.s1 to * (single suffix inference).
.Pp
A complete inference rule is a dependency line with such a target, the
normal dependency operator, no prerequisites and a list of shell commands.
.Pp
When
.Nm
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.
.Pp
For instance, with the following Makefile, describing a C program compiled
from sources a.c and b.c, with header file a.h:
.Bd -literal -offset indent
\&.SUFFIXES: .c .o
\&.c.o:
	${CC} ${CFLAGS} -c $<

prog: a.o b.o
	${CC} ${CFLAGS} -o $@ a.o b.o

a.o b.o: a.h

b.o: b.c
	${CC} -DFOO ${CFLAGS} -o $@ $<
.Ed
.Pp
Consider b.o:
there is a complete target rule re-creating it from b.c, so
it will be compiled using ${CC} -DFOO.
.Pp
Consider a.o:
there is no explicit target rule, so
.Nm
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}.
.Pp
Note that extra prerequisites are still taken into account, so both a.o
and b.o depend on a.h for re-creation.
.Pp
Valid suffixes accumulate over
.Ic .SUFFIXES
lines.
An empty
.Ic .SUFFIXES
can be used to reset the currently valid list of suffixes,
but inference rules already read are still known by
.Nm ,
and they are marked as inactive.
Redefining the corresponding suffix (or suffixes) will reactivate the rule.
.Pp
In case of duplicate inference rules with the same suffix combination,
the new rule overrides the old one.
.Pp
For maximal portability, suffixes should start with a dot.
.Sh VARIABLE ASSIGNMENTS
Variables in
.Nm
are much like variables in the shell and, by tradition,
consist of all upper-case letters.
They are also called
.Sq macros
in various texts.
For portability, only periods, underscores, digits and letters should be
used for variable names.
The following operators can be used to assign values to variables:
.Bl -tag -width Ds
.It Ic \&=
Assign the value to the variable.
Any previous value is overridden.
.It Ic \&:=
Assign with expansion, i.e., expand the value before assigning it
to the variable (extension).
.It Ic \&+=
Append the value to the current value of the variable (extension).
.It Ic \&?=
Assign the value to the variable if it is not already defined
.Po
.Bx
extension
.Pc .
Normally, expansion is not done until the variable is referenced.
.It Ic \&!=
Perform variable expansion and pass the result to the shell for
execution on the spot, assigning the result to the variable.
Any newlines in the result are also replaced with spaces
.Po
.Bx
extension
.Pc .
.It Ic \&!!=
Perform variable expansion on the spot and pass the result to the shell
for execution only when the value is needed, assigning the result to
the variable.
.Pp
This is almost identical to
.Ic \&!=
except that a shell is only run when the variable value is needed.
Any newlines in the result are also replaced with spaces
.Po
.Ox
extension
.Pc .
.El
.Pp
Any whitespace before the assigned
.Ar 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.
.Pp
Several extended assignment operators may be combined together.
For instance,
.Bd -literal -offset indent
A ?!= cmd
.Ed
.Pp
will only run
.Qq cmd
and put its output into
.Va A
if
.Va A
is not yet defined.
.Pp
Combinations that do not make sense, such as
.Bd -literal -offset indent
A +!!= cmd
.Ed
.Pp
will not work.
.Pp
Variables are expanded by surrounding the variable name with either
curly braces
.Pq Ql {}
or parentheses
.Pq Ql ()
and preceding it with
a dollar sign
.Pq Ql \&$ .
If the variable name contains only a single letter, the surrounding
braces or parentheses are not required.
This shorter form is not recommended.
.Pp
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.
.Pp
The four different classes of variables (in order of increasing precedence)
are:
.Bl -tag -width Ds
.It Environment variables
Variables defined as part of
.Nm make Ns 's
environment.
.It Global variables
Variables defined in the makefile or in included makefiles.
.It Command line variables
Variables defined as part of the command line.
.It Local variables
Variables that are defined specific to a certain target.
Standard local variables are as follows:
.Bl -tag -width ".ARCHIVE"
.It Va @
The name of the target.
.It Va \&%
The name of the archive member (only valid for library rules).
.It Va \&!
The name of the archive file (only valid for library rules).
.It Va \&?
The list of prerequisites for this target that were deemed out of date.
.It Va \&<
The name of the prerequisite from which this target is to be built, if a valid
inference rule (suffix rule) is in scope.
.It Va *
The file prefix of the file, containing only the file portion,
no suffix or preceding directory components.
.El
.Pp
The six variables
.Sq Va "@F" ,
.Sq Va "@D" ,
.Sq Va "<F" ,
.Sq Va "<D" ,
.Sq Va "*F" ,
and
.Sq Va "*D"
yield the
.Qq filename
and
.Qq directory
parts of the corresponding macros.
.Pp
For maximum compatibility,
.Sq Va \&<
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
.Bd -literal -offset indent
\&.SUFFIXES: .c .o
file.o: file.c
	cmd1 $<

\&.c.o:
	cmd2
.Ed
.Pp
building
.Pa file.o
will execute
.Qq cmd1 file.c .
.Pp
As an extension,
.Nm
supports the following local variables:
.Bl -tag -width ".ARCHIVE"
.It Va \&>
The list of all prerequisites for this target.
.It Va .ALLSRC
Synonym for
.Sq Va \&> .
.It Va .ARCHIVE
Synonym for
.Sq Va \&! .
.It Va .IMPSRC
Synonym for
.Sq Va \&< .
.It Va .MEMBER
Synonym for
.Sq Va \&% .
.It Va .OODATE
Synonym for
.Sq Va \&? .
.It Va .PREFIX
Synonym for
.Sq Va * .
.It Va .TARGET
Synonym for
.Sq Va @ .
.El
.Pp
These variables may be used on the dependency half of dependency
lines, when they make sense.
.El
.Pp
In addition,
.Nm
sets or knows about the following internal variables, or environment
variables:
.Bl -tag -width MAKEFLAGS
.It Va \&$
A single dollar sign
.Ql \&$ ,
i.e.,
.Ql \&$$
expands to a single dollar
sign.
.It Va .MAKE
The name that
.Nm
was executed with
.Pq Va argv Ns Op 0 .
.It Va .CURDIR
A path to the directory where
.Nm
was executed.
.It Va .OBJDIR
Path to the directory where targets are built.
At startup,
.Nm
searches for an alternate directory to place target files.
.Nm
tries to
.Xr chdir 2
into
.Ev MAKEOBJDIR
(or
.Pa obj
if
.Ev MAKEOBJDIR
is not defined),
and sets
.Va .OBJDIR
accordingly.
Should that fail,
.Va .OBJDIR
is set to
.Va .CURDIR .
.It Va MAKEFILE_LIST
The list of files read by
.Nm .
.It Va .MAKEFLAGS
The environment variable
.Ev MAKEFLAGS
may contain anything that
may be specified on
.Nm make Ns 's
command line.
Its contents are stored in
.Nm make Ns 's
.Va .MAKEFLAGS
variable.
Anything specified on
.Nm make Ns 's
command line is appended to the
.Va .MAKEFLAGS
variable which is then
entered into the environment as
.Ev MAKEFLAGS
for all programs which
.Nm
executes.
.It Va MFLAGS
A shorter synonym for
.Va .MAKEFLAGS .
.It Ev PWD
Alternate path to the current directory.
.Nm
normally sets
.Sq Va .CURDIR
to the canonical path given by
.Xr getcwd 3 .
However, if the environment variable
.Ev PWD
is set and gives a path to the current directory, then
.Nm
sets
.Sq Va .CURDIR
to the value of
.Ev PWD
instead.
.Ev PWD
is always set to the value of
.Sq Va .OBJDIR
for all programs which
.Nm
executes.
.It Va .TARGETS
List of targets
.Nm
is currently building.
.It Va MACHINE
Name of the machine architecture
.Nm
is running on, obtained from the
.Ev MACHINE
environment variable, or through
.Xr uname 3
if not defined.
.It Va MACHINE_ARCH
Name of the machine architecture
.Nm
was compiled for, obtained from the
.Ev MACHINE_ARCH
environment variable, or defined at compilation time.
.It Va MACHINE_CPU
Name of the machine processor
.Nm
was compiled for, obtained from the
.Ev 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
.Ev MACHINE_ARCH .
.It Va MAKEFILE
Possibly the file name of the last makefile that has been read.
It should not be used; see the
.Sx BUGS
section below.
.El
.Pp
Variable expansion may be modified to select or modify each word of the
variable (where
.Dq word
is a whitespace delimited sequence of characters).
The general format of a variable expansion is as follows:
.Pp
.Dl {variable[:modifier[:...]]}
.Pp
Each modifier begins with a colon and one of the following
special characters.
The colon may be escaped with a backslash
.Pq Ql \e .
.Bl -tag -width Ds
.It Cm :E
Replaces each word in the variable with its suffix.
.It Cm :H
Replaces each word in the variable with everything but the last component.
.It Cm :L
Replaces each word in the variable with its lower case equivalent.
.It Cm :U
Replaces each word in the variable with its upper case equivalent.
.It Cm :M Ns Ar pattern
Select only those words that match the rest of the modifier.
The standard shell wildcard characters
.Pf ( Ql * ,
.Ql \&? ,
and
.Ql [] )
may
be used.
The wildcard characters may be escaped with a backslash
.Pq Ql \e .
.It Cm :N Ns Ar pattern
This is identical to
.Cm :M ,
but selects all words which do not match
the rest of the modifier.
.It Cm :Q
Quotes every shell meta-character in the variable, so that it can be passed
safely through recursive invocations of
.Nm make .
.It Cm :QL
Quote list: quotes every shell meta-character in the variable, except
whitespace, so that it can be passed to a shell's
.Sq for
loops.
.It Cm :R
Replaces each word in the variable with everything but its suffix.
.Sm off
.It Cm :S No \&/ Ar old_string Xo
.No \&/ Ar new_string
.No \&/ Op Cm 1g
.Xc
.Sm on
Modify the first occurrence of
.Ar old_string
in the variable's value, replacing it with
.Ar new_string .
If a
.Ql g
is appended to the last slash of the pattern, all occurrences
in each word are replaced.
If a
.Ql 1
is appended to the last slash of the pattern, only the first word
is affected.
If
.Ar old_string
begins with a caret
.Pq Ql ^ ,
.Ar old_string
is anchored at the beginning of each word.
If
.Ar old_string
ends with a dollar sign
.Pq Ql \&$ ,
it is anchored at the end of each word.
Inside
.Ar new_string ,
an ampersand
.Pq Ql &
is replaced by
.Ar old_string
(without any
.Ql ^
or
.Ql \&$ ) .
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
.Pq Ql \e .
.Pp
Variable expansion occurs in the normal fashion inside both
.Ar old_string
and
.Ar new_string
with the single exception that a backslash is used to prevent the expansion
of a dollar sign
.Pq Ql \&$ ,
not a preceding dollar sign as is usual.
.Sm off
.It Cm :C No \&/ Ar pattern Xo
.No \&/ Ar replacement
.No \&/ Op Cm 1g
.Xc
.Sm on
The
.Cm :C
modifier is just like the
.Cm :S
modifier except that the old and new strings, instead of being
simple strings, are an extended regular expression (see
.Xr re_format 7 )
and an
.Xr ed 1 Ns \-style
replacement string.
Normally, the first occurrence of the pattern in
each word of the value is changed.
The
.Ql 1
modifier causes the substitution to apply to at most one word; the
.Ql 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
.Ql 1
and
.Ql g
are orthogonal; the former specifies whether multiple words are
potentially affected, the latter whether multiple substitutions can
potentially occur within each affected word.
.It Cm :T
Replaces each word in the variable with its last component.
.It Ar :old_string Ns = Ns Ar new_string
This is the
.At V
style variable substitution.
It must be the last modifier specified.
If
.Ar old_string
or
.Ar new_string
do not contain the pattern matching character
.Sq %
then it is assumed that they are
anchored at the end of each word, so only suffixes or entire
words may be replaced.
Otherwise
.Sq %
is the substring of
.Ar old_string
to be replaced in
.Ar new_string .
The right hand side
.Pq Ar new_string
may contain variable values, which will be expanded.
To put an actual single dollar, just double it.
.El
.Pp
All modifiers are
.Bx
extensions, except for the standard
.At V
style variable substitution.
.Pp
The interpretation of
.Sq %
and
.Sq $
in
.At V
variable substitutions is not mandated by POSIX, though it is
fairly common.
.Sh INCLUDE STATEMENTS, CONDITIONALS AND FOR LOOPS
Makefile inclusion, conditional structures and for loops reminiscent
of the C programming language are provided in
.Nm make .
All such structures are identified by a line beginning with a single
dot
.Pq Ql \&.
character.
Whitespace characters may follow this dot, e.g.,
.Bd -literal -offset indent
\&.include <file>
.Ed
and
.Bd -literal -offset indent -compact
\&.   include <file>
.Ed
.Pp
are identical constructs.
Files are included with either
.Ql .include <file>
or
.Ql .include Qq 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
.Fl I
option are searched before the system
makefile directory.
.Pp
Conditional expressions are also preceded by a single dot as the first
character of a line.
The possible conditionals are as follows:
.Bl -tag -width Ds
.It Ic .undef Ar variable
Un-define the specified global variable.
Only global variables may be un-defined.
.It Ic .poison Ar variable
Poison the specified global variable.
Any further reference to
.Ar variable
will be flagged as an error.
.It Ic .poison !defined Pq Ar variable
It is an error to try to use the value of
.Ar variable
in a context where it is not defined.
.It Ic .poison empty Pq Ar variable
It is an error to try to use the value of
.Ar variable
in a context where it is not defined or is empty.
.It Xo
.Ic \&.if
.Oo \&! Oc Ns Ar expression
.Op Ar operator expression ...
.Xc
Test the value of an expression.
.It Xo
.Ic .ifdef
.Oo \&! Oc Ns Ar variable
.Op Ar operator variable ...
.Xc
Test the value of a variable.
.It Xo
.Ic .ifndef
.Oo \&! Oc Ns Ar variable
.Op Ar operator variable ...
.Xc
Test the value of a variable.
.It Xo
.Ic .ifmake
.Oo \&! Oc Ns Ar target
.Op Ar operator target ...
.Xc
Test the target being built.
.It Xo
.Ic .ifnmake
.Oo \&! Oc Ns Ar target
.Op Ar operator target ...
.Xc
Test the target being built.
.It Ic .else
Reverse the sense of the last conditional.
.It Xo
.Ic .elif
.Oo \&! Oc Ns Ar expression
.Op Ar operator expression ...
.Xc
A combination of
.Sq Ic .else
followed by
.Sq Ic .if .
.It Xo
.Ic .elifdef
.Oo \&! Oc Ns Ar variable
.Op Ar operator variable ...
.Xc
A combination of
.Sq Ic .else
followed by
.Sq Ic .ifdef .
.It Xo
.Ic .elifndef
.Oo \&! Oc Ns Ar variable
.Op Ar operator variable ...
.Xc
A combination of
.Sq Ic .else
followed by
.Sq Ic .ifndef .
.It Xo
.Ic .elifmake
.Oo \&! Oc Ns Ar target
.Op Ar operator target ...
.Xc
A combination of
.Sq Ic .else
followed by
.Sq Ic .ifmake .
.It Xo
.Ic .elifnmake
.Oo \&! Oc Ns Ar target
.Op Ar operator target ...
.Xc
A combination of
.Sq Ic .else
followed by
.Sq Ic .ifnmake .
.It Ic .endif
End the body of the conditional.
.El
.Pp
The
.Ar operator
may be any one of the following:
.Bl -tag -width "Cm XX"
.It Cm ||
logical OR
.It Cm \&&&
Logical AND; of higher precedence than
.Cm || .
.El
.Pp
As in C,
.Nm
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
.Sq Ic \&!
may be used to logically negate an entire
conditional.
It is of higher precedence than
.Sq Ic \&&& .
.Pp
The value of
.Ar expression
may be any of the following:
.Bl -tag -width commands
.It Ic 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.
.It Ic defined
Takes a variable name as an argument and evaluates to true if the variable
has been defined.
.It Ic make
Takes a target name as an argument and evaluates to true if the target
was specified as part of
.Nm make Ns 's
command line or was declared the default target (either implicitly or
explicitly, see
.Va .MAIN )
before the line containing the conditional.
.It Ic empty
Takes a variable, with possible modifiers, and evaluates to true if
the expansion of the variable would result in an empty string.
.It Ic 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
.Va .PATH ) .
.It Ic target
Takes a target name as an argument and evaluates to true if the target
has been defined.
.El
.Pp
.Ar 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
.Sq Ic ==
or
.Sq Ic "!="
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.
.Pp
When
.Nm
is evaluating one of these conditional expressions, and it encounters
a word it doesn't recognize, either the
.Dq make
or
.Dq defined
expression is applied to it, depending on the form of the conditional.
If the form is
.Sq Ic .ifdef
or
.Sq Ic .ifndef ,
the
.Dq defined
expression is applied.
Similarly, if the form is
.Sq Ic .ifmake
or
.Sq Ic .ifnmake ,
the
.Dq make
expression is applied.
.Pp
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
.Sq Ic .else
or
.Sq Ic .endif
is found.
.Pp
For loops are typically used to apply a set of rules to a list of files.
The syntax of a for loop is:
.Bd -unfilled -offset indent
.Ic .for Ar variable Oo Ar variable ... Oc Ic in Ar expression
	<make-rules>
.Ic .endfor
.Ed
.Pp
After the for
.Ar expression
is evaluated, it is split into words.
On each iteration of the loop, one word is assigned to each
.Ar variable ,
in order,
and these
.Ar variables
are substituted in the
.Ic 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.
.Pp
Loops and conditional expressions may nest arbitrarily, but
they may not cross include file boundaries.
.Pp
.Nm
also supports
.Ic sinclude
and
.Ic -include
for compatibility with other implementations.
Both use the same syntax:
.Bd -unfilled -offset indent
.Ic sinclude Pa file
.Ic -include Pa file
.Ed
.Pp
.Po
note no quotes around
.Pa file
.Pc
and will include
.Pa file ,
but without any error if it does not exist.
.Sh COMMENTS
Comments begin with a hash
.Pq Ql \&#
character, anywhere but in a shell
command line, and continue to the end of the line
(but a
.Pq Ql \&#
character in a shell command line will be interpreted as a comment by
the shell).
.Sh TARGET ATTRIBUTES
Some targets may be tagged with some specific attributes by one
of the
.Sx SPECIAL TARGETS
or
.Sx SPECIAL PREREQUISITES
described below.
.Bl -tag -width "Ignoring errors"
.It Dq Always build
Run the commands associated with this target even if the
.Fl n
or
.Fl t
options were specified.
Can be used to mark recursive
.Nm make Ns 's ,
but prefer standard
.Sq Ic + Ns Ar cmd .
.It Dq Cheap
In parallel mode, don't scan the commands for occurrences of
.Nm ,
thus letting normal recursive
.Fl j
behavior apply.
.It Dq Expensive
In parallel mode, assume commands will invoke recursive commands.
Once
.Nm
starts building an expensive target, it won't start building anything else
until that target has finished building.
.It Dq Ignoring errors
Ignore any errors generating by running shell commands, exactly
as if they were all preceded by a dash
.Pq Ql \- .
.It Dq 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).
.Pp
Phony targets are always out of date at the start of a run, but
.Nm
still keeps track of when they are built (that is, when the associated
command list finishes running).
.It Dq Precious
Don't remove the target if
.Nm
is interrupted in the middle of building it.
.It Dq Silent
Do not display shell commands before running them, exactly as
if they were all preceded by a
.Sq @ .
.El
.Sh SPECIAL TARGETS
.Nm
recognizes standard special targets:
.Bl -tag -width ".NOTPARALLEL"
.It Ic .DEFAULT
If there is a
.Ic .DEFAULT
target rule, with commands but no prerequisites, and
.Nm
can't figure out another way to build a target, it will use that
list of commands, setting
.Va \&<
and
.Va @
appropriately.
.It Ic .IGNORE
Mark its prerequisites as
.Dq Ignoring errors .
.Pp
If the list of prerequisites is empty, apply that to all targets, exactly
like the
.Fl i
command-line option.
.It Ic .PRECIOUS
Mark its prerequisites as
.Dq Precious .
.Pp
If the list of prerequisites is empty, apply that to all targets.
.It Ic .SILENT
Mark its prerequisites as
.Dq Silent .
.Pp
If the list of prerequisites is empty, apply that to all targets, exactly
like the
.Fl s
command-line option.
.It Ic .SUFFIXES
See
.Sx INFERENCE RULES .
.El
.Pp
and also some other special targets as an extension:
.Bl -tag -width ".NOTPARALLEL"
.It Ic .BEGIN
Command lines attached to this target are executed before anything
else is done.
.It Ic .CHEAP
Mark its prerequisites as
.Dq Cheap .
.It Ic .END
Command lines attached to this target are executed at the end of a successful
run.
.It Ic .EXPENSIVE
Mark its prerequisites as
.Dq Expensive .
.It Ic .INTERRUPT
Command lines attached to this target are executed if
.Nm
is interrupted by a SIGINT.
.It Ic .MAKE
Mark its prerequisites as
.Dq Always build .
Prefer standard
.Sq Ic + Ns Ar cmd .
.It Ic .MAIN
If no target is specified when
.Nm
is invoked, this target will be built.
This is always set, either
explicitly, or implicitly when
.Nm
selects the default target, to give the user a way to refer to the default
target on the command line.
.It Ic .MAKEFLAGS
This target provides a way to specify flags for
.Nm
when the makefile is used.
The flags are as if typed to the shell, though the
.Fl f
option will have
no effect.
.It Ic .NOTPARALLEL
Disable parallel mode for the current makefile.
The
.Fl j
option is still passed to submakes.
.It Ic .NO_PARALLEL
Same as above, for compatibility with other pmake variants.
.It Ic .ORDER
The list of prerequisites should be built in sequence.
.It Ic .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.
.It Ic .PATH\fI.suffix\fR
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,
.Nm
will first look in that path, before reverting to the default search path.
.It Ic .PHONY
Mark its prerequisites as
.Dq Phony
targets.
.El
.Pp
It is an error to use several special targets, or a special target and
normal targets, in a single dependency line.
.Sh 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.
.Pp
This is an extension, even for standard special targets.
.Pp
.Nm
also recognizes some other prerequisites:
.Bl -tag -width ".PRECIOUS"
.It Ic .NOTMAIN
Normally
.Nm
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.
.It Ic .OPTIONAL
If a target is marked with this attribute and
.Nm
can't figure out how to create it, it will ignore this fact and assume
the file isn't needed or already exists.
.It Ic .USE
Turn the target into
.Nm make Ns '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
.Ic .USE )
of the
prerequisite.
If the target already has commands, the
.Ic .USE
target's commands are appended
to them.
.It Ic .WAIT
If
.Ic .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.
.El
.Sh ENVIRONMENT
.Nm
uses the following environment variables, if they exist:
.Ev MACHINE ,
.Ev MACHINE_ARCH ,
.Ev MACHINE_CPU ,
.Ev MAKEFLAGS ,
.Ev MAKEOBJDIR
and
.Ev PWD .
.Nm
also ignores and unsets
.Ev CDPATH .
.Sh FILES
.Bl -tag -width /usr/share/mk -compact
.It Pa .depend
list of dependencies
.It Pa makefile
default makefile
.It Pa Makefile
default makefile if
.Pa makefile
does not exist
.It Pa sys.mk
system makefile
.It Pa /usr/share/mk
system makefile directory
.El
.Sh EXIT STATUS
If
.Fl q
was specified, the
.Nm
utility exits with one of the following values:
.Pp
.Bl -tag -width Ds -offset indent -compact
.It 0
Normal behavior.
.It 1
The target was not up to date.
.It >1
An error occurred.
.El
.Pp
Otherwise, the
.Nm
utility exits with a value of 0 on success, and >0 if an error occurred.
.Sh SEE ALSO
.Xr ed 1 ,
.Xr mkdep 1 ,
.Xr sh 1 ,
.Xr getcwd 3 ,
.Xr uname 3 ,
.Xr re_format 7
.Rs
.%A S. I. Feldman
.%T Make \(em A Program for Maintaining Computer Programs
.\".%R Computing Science Technical Report
.\".%N 57
.%J Software \(em Practice and Experience
.%V 9:4
.%P pp. 255-265
.%D April 1979
.Re
.Rs
.\" 4.4BSD PSD:12
.%A Adam de Boor
.%T PMake \(em A Tutorial
.%B 4.4BSD Programmer's Supplementary Documents (PSD)
.Re
.Sh STANDARDS
The
.Nm
utility is mostly compliant with the
.St -p1003.1-2008
specification,
though its presence is optional.
.Pp
The flags
.Op Fl BCDdIjmV
are extensions to that specification.
.Pp
Older versions of
.Nm
used
.Ev MAKE
instead of
.Ev MAKEFLAGS .
This was removed for POSIX compatibility.
The internal variable
.Va MAKE
is set to the same value as
.Va .MAKE .
Support for this may be removed in the future.
.Pp
Most of the more esoteric features of
.Nm
should probably be avoided for greater compatibility.
.Sh HISTORY
A
.Nm
command appeared in
.At v7 .
.Pp
This implementation is a distant derivative of
.Nm pmake ,
originally written by Adam de Boor.
.Sh BUGS
If the same target is specified several times in complete target rules,
.Nm
silently ignores all commands after the first non empty set of commands,
e.g., in
.Bd -literal -offset indent
a:
	@echo "Executed"
a:
	@echo "Bad luck"
.Ed
.Pp
@echo "Bad luck" will be ignored.
.Pp
.Va .TARGETS
is not set to the default target when
.Nm
is invoked without a target name and no
.Ic MAIN
special target exists.
.Pp
The evaluation of
.Ar expression
in a test is somewhat simplistic.
Variables don't need to be quoted, but strings do:
Tests like
.Ql .if ${VAR} == "string" ,
.Ql .if ${VAR} >= 5 ,
.Ql .if 5 <= 10 ,
and
.Ql .if "string" == ${VAR}
do work, but
.Ql .if string = ${VAR}
doesn't.
.Pp
For loops are expanded before tests, so a fragment such as:
.Bd -literal -offset indent
\&.for TMACHINE in ${SHARED_ARCHS}
\&.if "${TMACHINE}" == ${MACHINE}
     ...
\&.endif
\&.endfor
.Ed
.Pp
requires the quotes.
.Pp
When handling
.Pf pre- Bx 4.4
archives,
.Nm
may erroneously mark archive members as out of date if the archive name
was truncated.
.Pp
The handling of
.Sq ;\&
and other special characters in tests may be utterly bogus.
For instance, in
.Bd -literal -offset indent
\&A=abcd;c.c
\&.if ${A:R} == "abcd;c"
.Ed
.Pp
the test will never match, even though the value is correct.
.Pp
In a .for loop, only the variable value is used; assignments will be
evaluated later, e.g., in
.Bd -literal -offset indent
\&.for I in a b c d
I:=${I:S/a/z/}
A+=$I
\&.endfor
.Ed
.Pp
.Sq A
will evaluate to a b c d after the loop, not z b c d.
.Pp
.Ic ORDER
is currently only used in parallel mode, so
keep prerequisites ordered for sequential mode!
.Pp
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
.Nm
from finding a rule to solve a dependency if the target name is not
exactly the same as the dependency.
.Pp
In parallel mode,
.Fl j Ar n
only limits the number of direct children of
.Nm .
During recursive invocations, each level may multiply the total number
of processes by
.Ar n .
However,
.Nm
includes some heuristics to try to prevent catastrophic behavior:
if a command is marked as expensive, or preceded by
.Sq + ,
or seems to
invoke a program that looks sufficiently like
.Sq make ,
.Nm
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
.Nm
will increase linearly with each level of recursion instead of exponentially.
.Pp
The
.Va 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.