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32 .Dd August 15, 2016
33 .Dt MAKE 1
34 .Os
35 .Sh NAME
36 .Nm make
37 .Nd maintain program dependencies
38 .Sh SYNOPSIS
39 .Nm
40 .Op Fl BeikNnqrstWwX
41 .Op Fl C Ar directory
42 .Op Fl D Ar variable
43 .Op Fl d Ar flags
44 .Op Fl f Ar makefile
45 .Op Fl I Ar directory
46 .Op Fl J Ar private
47 .Op Fl j Ar max_jobs
48 .Op Fl m Ar directory
49 .Op Fl T Ar file
50 .Op Fl V Ar variable
51 .Op Ar variable=value
52 .Op Ar target ...
53 .Sh DESCRIPTION
54 .Nm
55 is a program designed to simplify the maintenance of other programs.
56 Its input is a list of specifications as to the files upon which programs
57 and other files depend.
58 If no
59 .Fl f Ar makefile
60 makefile option is given,
61 .Nm
62 will try to open
63 .Ql Pa makefile
64 then
65 .Ql Pa Makefile
66 in order to find the specifications.
67 If the file
68 .Ql Pa .depend
69 exists, it is read (see
70 .Xr mkdep 1 ) .
71 .Pp
72 This manual page is intended as a reference document only.
73 For a more thorough description of
74 .Nm
75 and makefiles, please refer to
76 .%T "PMake \- A Tutorial" .
77 .Pp
78 .Nm
79 will prepend the contents of the
80 .Va MAKEFLAGS
81 environment variable to the command line arguments before parsing them.
82 .Pp
83 The options are as follows:
84 .Bl -tag -width Ds
85 .It Fl B
86 Try to be backwards compatible by executing a single shell per command and
87 by executing the commands to make the sources of a dependency line in sequence.
88 .It Fl C Ar directory
89 Change to
90 .Ar directory
91 before reading the makefiles or doing anything else.
92 If multiple
93 .Fl C
94 options are specified, each is interpreted relative to the previous one:
95 .Fl C Pa / Fl C Pa etc
96 is equivalent to
97 .Fl C Pa /etc .
98 .It Fl D Ar variable
99 Define
100 .Ar variable
101 to be 1, in the global context.
102 .It Fl d Ar [-]flags
103 Turn on debugging, and specify which portions of
104 .Nm
105 are to print debugging information.
106 Unless the flags are preceded by
107 .Ql \-
108 they are added to the
109 .Va MAKEFLAGS
110 environment variable and will be processed by any child make processes.
111 By default, debugging information is printed to standard error,
112 but this can be changed using the
113 .Ar F
114 debugging flag.
115 The debugging output is always unbuffered; in addition, if debugging
116 is enabled but debugging output is not directed to standard output,
117 then the standard output is line buffered.
118 .Ar Flags
119 is one or more of the following:
120 .Bl -tag -width Ds
121 .It Ar A
122 Print all possible debugging information;
123 equivalent to specifying all of the debugging flags.
124 .It Ar a
125 Print debugging information about archive searching and caching.
126 .It Ar C
127 Print debugging information about current working directory.
128 .It Ar c
129 Print debugging information about conditional evaluation.
130 .It Ar d
131 Print debugging information about directory searching and caching.
132 .It Ar e
133 Print debugging information about failed commands and targets.
134 .It Ar F Ns Oo Sy \&+ Oc Ns Ar filename
135 Specify where debugging output is written.
136 This must be the last flag, because it consumes the remainder of
137 the argument.
138 If the character immediately after the
139 .Ql F
140 flag is
141 .Ql \&+ ,
142 then the file will be opened in append mode;
143 otherwise the file will be overwritten.
144 If the file name is
145 .Ql stdout
146 or
147 .Ql stderr
148 then debugging output will be written to the
149 standard output or standard error output file descriptors respectively
150 (and the
151 .Ql \&+
152 option has no effect).
153 Otherwise, the output will be written to the named file.
154 If the file name ends
155 .Ql .%d
156 then the
157 .Ql %d
158 is replaced by the pid.
159 .It Ar f
160 Print debugging information about loop evaluation.
161 .It Ar "g1"
162 Print the input graph before making anything.
163 .It Ar "g2"
164 Print the input graph after making everything, or before exiting
165 on error.
166 .It Ar "g3"
167 Print the input graph before exiting on error.
168 .It Ar j
169 Print debugging information about running multiple shells.
170 .It Ar l
171 Print commands in Makefiles regardless of whether or not they are prefixed by
172 .Ql @
173 or other "quiet" flags.
174 Also known as "loud" behavior.
175 .It Ar M
176 Print debugging information about "meta" mode decisions about targets.
177 .It Ar m
178 Print debugging information about making targets, including modification
179 dates.
180 .It Ar n
181 Don't delete the temporary command scripts created when running commands.
182 These temporary scripts are created in the directory
183 referred to by the
184 .Ev TMPDIR
185 environment variable, or in
186 .Pa /tmp
187 if
188 .Ev TMPDIR
189 is unset or set to the empty string.
190 The temporary scripts are created by
191 .Xr mkstemp 3 ,
192 and have names of the form
193 .Pa makeXXXXXX .
194 .Em NOTE :
195 This can create many files in
196 .Ev TMPDIR
197 or
198 .Pa /tmp ,
199 so use with care.
200 .It Ar p
201 Print debugging information about makefile parsing.
202 .It Ar s
203 Print debugging information about suffix-transformation rules.
204 .It Ar t
205 Print debugging information about target list maintenance.
206 .It Ar V
207 Force the
208 .Fl V
209 option to print raw values of variables.
210 .It Ar v
211 Print debugging information about variable assignment.
212 .It Ar x
213 Run shell commands with
214 .Fl x
215 so the actual commands are printed as they are executed.
216 .El
217 .It Fl e
218 Specify that environment variables override macro assignments within
219 makefiles.
220 .It Fl f Ar makefile
221 Specify a makefile to read instead of the default
222 .Ql Pa makefile .
223 If
224 .Ar makefile
225 is
226 .Ql Fl ,
227 standard input is read.
228 Multiple makefiles may be specified, and are read in the order specified.
229 .It Fl I Ar directory
230 Specify a directory in which to search for makefiles and included makefiles.
231 The system makefile directory (or directories, see the
232 .Fl m
233 option) is automatically included as part of this list.
234 .It Fl i
235 Ignore non-zero exit of shell commands in the makefile.
236 Equivalent to specifying
237 .Ql Fl
238 before each command line in the makefile.
239 .It Fl J Ar private
240 This option should
241 .Em not
242 be specified by the user.
243 .Pp
244 When the
245 .Ar j
246 option is in use in a recursive build, this option is passed by a make
247 to child makes to allow all the make processes in the build to
248 cooperate to avoid overloading the system.
249 .It Fl j Ar max_jobs
250 Specify the maximum number of jobs that
251 .Nm
252 may have running at any one time.
253 The value is saved in
254 .Va .MAKE.JOBS .
255 Turns compatibility mode off, unless the
256 .Ar B
257 flag is also specified.
258 When compatibility mode is off, all commands associated with a
259 target are executed in a single shell invocation as opposed to the
260 traditional one shell invocation per line.
261 This can break traditional scripts which change directories on each
262 command invocation and then expect to start with a fresh environment
263 on the next line.
264 It is more efficient to correct the scripts rather than turn backwards
265 compatibility on.
266 .It Fl k
267 Continue processing after errors are encountered, but only on those targets
268 that do not depend on the target whose creation caused the error.
269 .It Fl m Ar directory
270 Specify a directory in which to search for sys.mk and makefiles included
271 via the
272 .Ao Ar file Ac Ns -style
273 include statement.
274 The
275 .Fl m
276 option can be used multiple times to form a search path.
277 This path will override the default system include path: /usr/share/mk.
278 Furthermore the system include path will be appended to the search path used
279 for
280 .Qo Ar file Qc Ns -style
281 include statements (see the
282 .Fl I
283 option).
284 .Pp
285 If a file or directory name in the
286 .Fl m
287 argument (or the
288 .Ev MAKESYSPATH
289 environment variable) starts with the string
290 .Qq \&.../
291 then
292 .Nm
293 will search for the specified file or directory named in the remaining part
294 of the argument string.
295 The search starts with the current directory of
296 the Makefile and then works upward towards the root of the file system.
297 If the search is successful, then the resulting directory replaces the
298 .Qq \&.../
299 specification in the
300 .Fl m
301 argument.
302 If used, this feature allows
303 .Nm
304 to easily search in the current source tree for customized sys.mk files
305 (e.g., by using
306 .Qq \&.../mk/sys.mk
307 as an argument).
308 .It Fl n
309 Display the commands that would have been executed, but do not
310 actually execute them unless the target depends on the .MAKE special
311 source (see below).
312 .It Fl N
313 Display the commands which would have been executed, but do not
314 actually execute any of them; useful for debugging top-level makefiles
315 without descending into subdirectories.
316 .It Fl q
317 Do not execute any commands, but exit 0 if the specified targets are
318 up-to-date and 1, otherwise.
319 .It Fl r
320 Do not use the built-in rules specified in the system makefile.
321 .It Fl s
322 Do not echo any commands as they are executed.
323 Equivalent to specifying
324 .Ql Ic @
325 before each command line in the makefile.
326 .It Fl T Ar tracefile
327 When used with the
328 .Fl j
329 flag,
330 append a trace record to
331 .Ar tracefile
332 for each job started and completed.
333 .It Fl t
334 Rather than re-building a target as specified in the makefile, create it
335 or update its modification time to make it appear up-to-date.
336 .It Fl V Ar variable
337 Print
338 .Nm Ns 's
339 idea of the value of
340 .Ar variable ,
341 in the global context.
342 Do not build any targets.
343 Multiple instances of this option may be specified;
344 the variables will be printed one per line,
345 with a blank line for each null or undefined variable.
346 If
347 .Ar variable
348 contains a
349 .Ql \&$
350 then the value will be expanded before printing.
351 .It Fl W
352 Treat any warnings during makefile parsing as errors.
353 .It Fl w
354 Print entering and leaving directory messages, pre and post processing.
355 .It Fl X
356 Don't export variables passed on the command line to the environment
357 individually.
358 Variables passed on the command line are still exported
359 via the
360 .Va MAKEFLAGS
361 environment variable.
362 This option may be useful on systems which have a small limit on the
363 size of command arguments.
364 .It Ar variable=value
365 Set the value of the variable
366 .Ar variable
367 to
368 .Ar value .
369 Normally, all values passed on the command line are also exported to
370 sub-makes in the environment.
371 The
372 .Fl X
373 flag disables this behavior.
374 Variable assignments should follow options for POSIX compatibility
375 but no ordering is enforced.
376 .El
377 .Pp
378 There are seven different types of lines in a makefile: file dependency
379 specifications, shell commands, variable assignments, include statements,
380 conditional directives, for loops, and comments.
381 .Pp
382 In general, lines may be continued from one line to the next by ending
383 them with a backslash
384 .Pq Ql \e .
385 The trailing newline character and initial whitespace on the following
386 line are compressed into a single space.
387 .Sh FILE DEPENDENCY SPECIFICATIONS
388 Dependency lines consist of one or more targets, an operator, and zero
389 or more sources.
390 This creates a relationship where the targets
391 .Dq depend
392 on the sources
393 and are usually created from them.
394 The exact relationship between the target and the source is determined
395 by the operator that separates them.
396 The three operators are as follows:
397 .Bl -tag -width flag
398 .It Ic \&:
399 A target is considered out-of-date if its modification time is less than
400 those of any of its sources.
401 Sources for a target accumulate over dependency lines when this operator
402 is used.
403 The target is removed if
404 .Nm
405 is interrupted.
406 .It Ic \&!
407 Targets are always re-created, but not until all sources have been
408 examined and re-created as necessary.
409 Sources for a target accumulate over dependency lines when this operator
410 is used.
411 The target is removed if
412 .Nm
413 is interrupted.
414 .It Ic \&::
415 If no sources are specified, the target is always re-created.
416 Otherwise, a target is considered out-of-date if any of its sources has
417 been modified more recently than the target.
418 Sources for a target do not accumulate over dependency lines when this
419 operator is used.
420 The target will not be removed if
421 .Nm
422 is interrupted.
423 .El
424 .Pp
425 Targets and sources may contain the shell wildcard values
426 .Ql \&? ,
427 .Ql * ,
428 .Ql [] ,
429 and
430 .Ql {} .
431 The values
432 .Ql \&? ,
433 .Ql * ,
434 and
435 .Ql []
436 may only be used as part of the final
437 component of the target or source, and must be used to describe existing
438 files.
439 The value
440 .Ql {}
441 need not necessarily be used to describe existing files.
442 Expansion is in directory order, not alphabetically as done in the shell.
443 .Sh SHELL COMMANDS
444 Each target may have associated with it one or more lines of shell
445 commands, normally
446 used to create the target.
447 Each of the lines in this script
448 .Em must
449 be preceded by a tab.
450 (For historical reasons, spaces are not accepted.)
451 While targets can appear in many dependency lines if desired, by
452 default only one of these rules may be followed by a creation
453 script.
454 If the
455 .Ql Ic \&::
456 operator is used, however, all rules may include scripts and the
457 scripts are executed in the order found.
458 .Pp
459 Each line is treated as a separate shell command, unless the end of
460 line is escaped with a backslash
461 .Pq Ql \e
462 in which case that line and the next are combined.
463 .\" The escaped newline is retained and passed to the shell, which
464 .\" normally ignores it.
465 .\" However, the tab at the beginning of the following line is removed.
466 If the first characters of the command are any combination of
467 .Ql Ic @ ,
468 .Ql Ic + ,
469 or
470 .Ql Ic \- ,
471 the command is treated specially.
472 A
473 .Ql Ic @
474 causes the command not to be echoed before it is executed.
475 A
476 .Ql Ic +
477 causes the command to be executed even when
478 .Fl n
479 is given.
480 This is similar to the effect of the .MAKE special source,
481 except that the effect can be limited to a single line of a script.
482 A
483 .Ql Ic \-
484 in compatibility mode
485 causes any non-zero exit status of the command line to be ignored.
486 .Pp
487 When
488 .Nm
489 is run in jobs mode with
490 .Fl j Ar max_jobs ,
491 the entire script for the target is fed to a
492 single instance of the shell.
493 In compatibility (non-jobs) mode, each command is run in a separate process.
494 If the command contains any shell meta characters
495 .Pq Ql #=|^(){};&<>*?[]:$`\e\en
496 it will be passed to the shell; otherwise
497 .Nm
498 will attempt direct execution.
499 If a line starts with
500 .Ql Ic \-
501 and the shell has ErrCtl enabled then failure of the command line
502 will be ignored as in compatibility mode.
503 Otherwise
504 .Ql Ic \-
505 affects the entire job;
506 the script will stop at the first command line that fails,
507 but the target will not be deemed to have failed.
508 .Pp
509 Makefiles should be written so that the mode of
510 .Nm
511 operation does not change their behavior.
512 For example, any command which needs to use
513 .Dq cd
514 or
515 .Dq chdir
516 without potentially changing the directory for subsequent commands
517 should be put in parentheses so it executes in a subshell.
518 To force the use of one shell, escape the line breaks so as to make
519 the whole script one command.
520 For example:
521 .Bd -literal -offset indent
522 avoid-chdir-side-effects:
523 @echo Building $@ in `pwd`
524 @(cd ${.CURDIR} && ${MAKE} $@)
525 @echo Back in `pwd`
527 ensure-one-shell-regardless-of-mode:
528 @echo Building $@ in `pwd`; \e
529 (cd ${.CURDIR} && ${MAKE} $@); \e
530 echo Back in `pwd`
531 .Ed
532 .Pp
533 Since
534 .Nm
535 will
536 .Xr chdir 2
537 to
538 .Ql Va .OBJDIR
539 before executing any targets, each child process
540 starts with that as its current working directory.
541 .Sh VARIABLE ASSIGNMENTS
542 Variables in make are much like variables in the shell, and, by tradition,
543 consist of all upper-case letters.
544 .Ss Variable assignment modifiers
545 The five operators that can be used to assign values to variables are as
546 follows:
547 .Bl -tag -width Ds
548 .It Ic \&=
549 Assign the value to the variable.
550 Any previous value is overridden.
551 .It Ic \&+=
552 Append the value to the current value of the variable.
553 .It Ic \&?=
554 Assign the value to the variable if it is not already defined.
555 .It Ic \&:=
556 Assign with expansion, i.e. expand the value before assigning it
557 to the variable.
558 Normally, expansion is not done until the variable is referenced.
559 .Em NOTE :
560 References to undefined variables are
561 .Em not
562 expanded.
563 This can cause problems when variable modifiers are used.
564 .It Ic \&!=
565 Expand the value and pass it to the shell for execution and assign
566 the result to the variable.
567 Any newlines in the result are replaced with spaces.
568 .El
569 .Pp
570 Any white-space before the assigned
571 .Ar value
572 is removed; if the value is being appended, a single space is inserted
573 between the previous contents of the variable and the appended value.
574 .Pp
575 Variables are expanded by surrounding the variable name with either
576 curly braces
577 .Pq Ql {}
578 or parentheses
579 .Pq Ql ()
580 and preceding it with
581 a dollar sign
582 .Pq Ql \&$ .
583 If the variable name contains only a single letter, the surrounding
584 braces or parentheses are not required.
585 This shorter form is not recommended.
586 .Pp
587 If the variable name contains a dollar, then the name itself is expanded first.
588 This allows almost arbitrary variable names, however names containing dollar,
589 braces, parenthesis, or whitespace are really best avoided!
590 .Pp
591 If the result of expanding a variable contains a dollar sign
592 .Pq Ql \&$
593 the string is expanded again.
594 .Pp
595 Variable substitution occurs at three distinct times, depending on where
596 the variable is being used.
597 .Bl -enum
598 .It
599 Variables in dependency lines are expanded as the line is read.
600 .It
601 Variables in shell commands are expanded when the shell command is
602 executed.
603 .It
604 .Dq .for
605 loop index variables are expanded on each loop iteration.
606 Note that other variables are not expanded inside loops so
607 the following example code:
608 .Bd -literal -offset indent
610 .Dv .for i in 1 2 3
611 a+= ${i}
612 j= ${i}
613 b+= ${j}
614 .Dv .endfor
616 all:
617 @echo ${a}
618 @echo ${b}
620 .Ed
621 will print:
622 .Bd -literal -offset indent
623 1 2 3
624 3 3 3
626 .Ed
627 Because while ${a} contains
628 .Dq 1 2 3
629 after the loop is executed, ${b}
630 contains
631 .Dq ${j} ${j} ${j}
632 which expands to
633 .Dq 3 3 3
634 since after the loop completes ${j} contains
635 .Dq 3 .
636 .El
637 .Ss Variable classes
638 The four different classes of variables (in order of increasing precedence)
639 are:
640 .Bl -tag -width Ds
641 .It Environment variables
642 Variables defined as part of
643 .Nm Ns 's
644 environment.
645 .It Global variables
646 Variables defined in the makefile or in included makefiles.
647 .It Command line variables
648 Variables defined as part of the command line.
649 .It Local variables
650 Variables that are defined specific to a certain target.
651 .El
652 .Pp
653 Local variables are all built in and their values vary magically from
654 target to target.
655 It is not currently possible to define new local variables.
656 The seven local variables are as follows:
657 .Bl -tag -width ".ARCHIVE" -offset indent
658 .It Va .ALLSRC
659 The list of all sources for this target; also known as
660 .Ql Va \&\*[Gt] .
661 .It Va .ARCHIVE
662 The name of the archive file; also known as
663 .Ql Va \&! .
664 .It Va .IMPSRC
665 In suffix-transformation rules, the name/path of the source from which the
666 target is to be transformed (the
667 .Dq implied
668 source); also known as
669 .Ql Va \&\*[Lt] .
670 It is not defined in explicit rules.
671 .It Va .MEMBER
672 The name of the archive member; also known as
673 .Ql Va % .
674 .It Va .OODATE
675 The list of sources for this target that were deemed out-of-date; also
676 known as
677 .Ql Va \&? .
678 .It Va .PREFIX
679 The file prefix of the target, containing only the file portion, no suffix
680 or preceding directory components; also known as
681 .Ql Va * .
682 The suffix must be one of the known suffixes declared with
683 .Ic .SUFFIXES
684 or it will not be recognized.
685 .It Va .TARGET
686 The name of the target; also known as
687 .Ql Va @ .
688 For compatibility with other makes this is an alias for
689 .Ic .ARCHIVE
690 in archive member rules.
691 .El
692 .Pp
693 The shorter forms
694 .Ql ( Va \*[Gt] ,
695 .Ql Va \&! ,
696 .Ql Va \*[Lt] ,
697 .Ql Va % ,
698 .Ql Va \&? ,
699 .Ql Va * ,
700 and
701 .Ql Va @ )
702 are permitted for backward
703 compatibility with historical makefiles and legacy POSIX make and are
704 not recommended.
705 .Pp
706 Variants of these variables with the punctuation followed immediately by
707 .Ql D
708 or
709 .Ql F ,
710 e.g.
711 .Ql Va $(@D) ,
712 are legacy forms equivalent to using the
713 .Ql :H
714 and
715 .Ql :T
716 modifiers.
717 These forms are accepted for compatibility with
718 .At V
719 makefiles and POSIX but are not recommended.
720 .Pp
721 Four of the local variables may be used in sources on dependency lines
722 because they expand to the proper value for each target on the line.
723 These variables are
724 .Ql Va .TARGET ,
725 .Ql Va .PREFIX ,
726 .Ql Va .ARCHIVE ,
727 and
728 .Ql Va .MEMBER .
729 .Ss Additional built-in variables
730 In addition,
731 .Nm
732 sets or knows about the following variables:
733 .Bl -tag -width .MAKEOVERRIDES
734 .It Va \&$
735 A single dollar sign
736 .Ql \&$ ,
737 i.e.
738 .Ql \&$$
739 expands to a single dollar
740 sign.
741 .It Va .ALLTARGETS
742 The list of all targets encountered in the Makefile.
743 If evaluated during
744 Makefile parsing, lists only those targets encountered thus far.
745 .It Va .CURDIR
746 A path to the directory where
747 .Nm
748 was executed.
749 Refer to the description of
750 .Ql Ev PWD
751 for more details.
752 .It Va .INCLUDEDFROMDIR
753 The directory of the file this Makefile was included from.
754 .It Va .INCLUDEDFROMFILE
755 The filename of the file this Makefile was included from.
756 .It Ev MAKE
757 The name that
758 .Nm
759 was executed with
760 .Pq Va argv[0] .
761 For compatibility
762 .Nm
763 also sets
764 .Va .MAKE
765 with the same value.
766 The preferred variable to use is the environment variable
767 .Ev MAKE
768 because it is more compatible with other versions of
769 .Nm
770 and cannot be confused with the special target with the same name.
771 .It Va .MAKE.DEPENDFILE
772 Names the makefile (default
773 .Ql Pa .depend )
774 from which generated dependencies are read.
775 .It Va .MAKE.EXPAND_VARIABLES
776 A boolean that controls the default behavior of the
777 .Fl V
778 option.
779 .It Va .MAKE.EXPORTED
780 The list of variables exported by
781 .Nm .
782 .It Va .MAKE.JOBS
783 The argument to the
784 .Fl j
785 option.
786 .It Va .MAKE.JOB.PREFIX
787 If
788 .Nm
789 is run with
790 .Ar j
791 then output for each target is prefixed with a token
792 .Ql --- target ---
793 the first part of which can be controlled via
794 .Va .MAKE.JOB.PREFIX .
795 If
796 .Va .MAKE.JOB.PREFIX
797 is empty, no token is printed.
798 .br
799 For example:
800 .Li .MAKE.JOB.PREFIX=${.newline}---${.MAKE:T}[${.MAKE.PID}]
801 would produce tokens like
802 .Ql ---make[1234] target ---
803 making it easier to track the degree of parallelism being achieved.
804 .It Ev MAKEFLAGS
805 The environment variable
806 .Ql Ev MAKEFLAGS
807 may contain anything that
808 may be specified on
809 .Nm Ns 's
810 command line.
811 Anything specified on
812 .Nm Ns 's
813 command line is appended to the
814 .Ql Ev MAKEFLAGS
815 variable which is then
816 entered into the environment for all programs which
817 .Nm
818 executes.
819 .It Va .MAKE.LEVEL
820 The recursion depth of
821 .Nm .
822 The initial instance of
823 .Nm
824 will be 0, and an incremented value is put into the environment
825 to be seen by the next generation.
826 This allows tests like:
827 .Li .if ${.MAKE.LEVEL} == 0
828 to protect things which should only be evaluated in the initial instance of
829 .Nm .
830 .It Va .MAKE.MAKEFILE_PREFERENCE
831 The ordered list of makefile names
832 (default
833 .Ql Pa makefile ,
834 .Ql Pa Makefile )
835 that
836 .Nm
837 will look for.
838 .It Va .MAKE.MAKEFILES
839 The list of makefiles read by
840 .Nm ,
841 which is useful for tracking dependencies.
842 Each makefile is recorded only once, regardless of the number of times read.
843 .It Va .MAKE.MODE
844 Processed after reading all makefiles.
845 Can affect the mode that
846 .Nm
847 runs in.
848 It can contain a number of keywords:
849 .Bl -hang -width missing-filemon=bf.
850 .It Pa compat
851 Like
852 .Fl B ,
853 puts
854 .Nm
855 into "compat" mode.
856 .It Pa meta
857 Puts
858 .Nm
859 into "meta" mode, where meta files are created for each target
860 to capture the command run, the output generated and if
861 .Xr filemon 4
862 is available, the system calls which are of interest to
863 .Nm .
864 The captured output can be very useful when diagnosing errors.
865 .It Pa curdirOk= Ar bf
866 Normally
867 .Nm
868 will not create .meta files in
869 .Ql Va .CURDIR .
870 This can be overridden by setting
871 .Va bf
872 to a value which represents True.
873 .It Pa missing-meta= Ar bf
874 If
875 .Va bf
876 is True, then a missing .meta file makes the target out-of-date.
877 .It Pa missing-filemon= Ar bf
878 If
879 .Va bf
880 is True, then missing filemon data makes the target out-of-date.
881 .It Pa nofilemon
882 Do not use
883 .Xr filemon 4 .
884 .It Pa env
885 For debugging, it can be useful to include the environment
886 in the .meta file.
887 .It Pa verbose
888 If in "meta" mode, print a clue about the target being built.
889 This is useful if the build is otherwise running silently.
890 The message printed the value of:
891 .Va .MAKE.META.PREFIX .
892 .It Pa ignore-cmd
893 Some makefiles have commands which are simply not stable.
894 This keyword causes them to be ignored for
895 determining whether a target is out of date in "meta" mode.
896 See also
897 .Ic .NOMETA_CMP .
898 .It Pa silent= Ar bf
899 If
900 .Va bf
901 is True, when a .meta file is created, mark the target
902 .Ic .SILENT .
903 .El
904 .It Va .MAKE.META.BAILIWICK
905 In "meta" mode, provides a list of prefixes which
906 match the directories controlled by
907 .Nm .
908 If a file that was generated outside of
909 .Va .OBJDIR
910 but within said bailiwick is missing,
911 the current target is considered out-of-date.
912 .It Va .MAKE.META.CREATED
913 In "meta" mode, this variable contains a list of all the meta files
914 updated.
915 If not empty, it can be used to trigger processing of
916 .Va .MAKE.META.FILES .
917 .It Va .MAKE.META.FILES
918 In "meta" mode, this variable contains a list of all the meta files
919 used (updated or not).
920 This list can be used to process the meta files to extract dependency
921 information.
922 .It Va .MAKE.META.IGNORE_PATHS
923 Provides a list of path prefixes that should be ignored;
924 because the contents are expected to change over time.
925 The default list includes:
926 .Ql Pa /dev /etc /proc /tmp /var/run /var/tmp
927 .It Va .MAKE.META.IGNORE_PATTERNS
928 Provides a list of patterns to match against pathnames.
929 Ignore any that match.
930 .It Va .MAKE.META.IGNORE_FILTER
931 Provides a list of variable modifiers to apply to each pathname.
932 Ignore if the expansion is an empty string.
933 .It Va .MAKE.META.PREFIX
934 Defines the message printed for each meta file updated in "meta verbose" mode.
935 The default value is:
936 .Dl Building ${.TARGET:H:tA}/${.TARGET:T}
937 .It Va .MAKEOVERRIDES
938 This variable is used to record the names of variables assigned to
939 on the command line, so that they may be exported as part of
940 .Ql Ev MAKEFLAGS .
941 This behavior can be disabled by assigning an empty value to
942 .Ql Va .MAKEOVERRIDES
943 within a makefile.
944 Extra variables can be exported from a makefile
945 by appending their names to
946 .Ql Va .MAKEOVERRIDES .
947 .Ql Ev MAKEFLAGS
948 is re-exported whenever
949 .Ql Va .MAKEOVERRIDES
950 is modified.
951 .It Va .MAKE.PATH_FILEMON
952 If
953 .Nm
954 was built with
955 .Xr filemon 4
956 support, this is set to the path of the device node.
957 This allows makefiles to test for this support.
958 .It Va .MAKE.PID
959 The process-id of
960 .Nm .
961 .It Va .MAKE.PPID
962 The parent process-id of
963 .Nm .
964 .It Va .MAKE.SAVE_DOLLARS
965 value should be a boolean that controls whether
966 .Ql $$
967 are preserved when doing
968 .Ql :=
969 assignments.
970 The default is false, for backwards compatibility.
971 Set to true for compatability with other makes.
972 If set to false,
973 .Ql $$
974 becomes
975 .Ql $
976 per normal evaluation rules.
977 .It Va MAKE_PRINT_VAR_ON_ERROR
978 When
979 .Nm
980 stops due to an error, it sets
981 .Ql Va .ERROR_TARGET
982 to the name of the target that failed,
983 .Ql Va .ERROR_CMD
984 to the commands of the failed target,
985 and in "meta" mode, it also sets
986 .Ql Va .ERROR_CWD
987 to the
988 .Xr getcwd 3 ,
989 and
990 .Ql Va .ERROR_META_FILE
991 to the path of the meta file (if any) describing the failed target.
992 It then prints its name and the value of
993 .Ql Va .CURDIR
994 as well as the value of any variables named in
995 .Ql Va MAKE_PRINT_VAR_ON_ERROR .
996 .It Va .newline
997 This variable is simply assigned a newline character as its value.
998 This allows expansions using the
999 .Cm \&:@
1000 modifier to put a newline between
1001 iterations of the loop rather than a space.
1002 For example, the printing of
1003 .Ql Va MAKE_PRINT_VAR_ON_ERROR
1004 could be done as ${MAKE_PRINT_VAR_ON_ERROR:@v@$v='${$v}'${.newline}@}.
1005 .It Va .OBJDIR
1006 A path to the directory where the targets are built.
1007 Its value is determined by trying to
1008 .Xr chdir 2
1009 to the following directories in order and using the first match:
1010 .Bl -enum
1011 .It
1012 .Ev ${MAKEOBJDIRPREFIX}${.CURDIR}
1013 .Pp
1014 (Only if
1015 .Ql Ev MAKEOBJDIRPREFIX
1016 is set in the environment or on the command line.)
1017 .It
1018 .Ev ${MAKEOBJDIR}
1019 .Pp
1020 (Only if
1021 .Ql Ev MAKEOBJDIR
1022 is set in the environment or on the command line.)
1023 .It
1024 .Ev ${.CURDIR} Ns Pa /obj. Ns Ev ${MACHINE}
1025 .It
1026 .Ev ${.CURDIR} Ns Pa /obj
1027 .It
1028 .Pa /usr/obj/ Ns Ev ${.CURDIR}
1029 .It
1030 .Ev ${.CURDIR}
1031 .El
1032 .Pp
1033 Variable expansion is performed on the value before it's used,
1034 so expressions such as
1035 .Dl ${.CURDIR:S,^/usr/src,/var/obj,}
1036 may be used.
1037 This is especially useful with
1038 .Ql Ev MAKEOBJDIR .
1039 .Pp
1040 .Ql Va .OBJDIR
1041 may be modified in the makefile via the special target
1042 .Ql Ic .OBJDIR .
1043 In all cases,
1044 .Nm
1045 will
1046 .Xr chdir 2
1047 to the specified directory if it exists, and set
1048 .Ql Va .OBJDIR
1049 and
1050 .Ql Ev PWD
1051 to that directory before executing any targets.
1052 .
1053 .It Va .PARSEDIR
1054 A path to the directory of the current
1055 .Ql Pa Makefile
1056 being parsed.
1057 .It Va .PARSEFILE
1058 The basename of the current
1059 .Ql Pa Makefile
1060 being parsed.
1061 This variable and
1062 .Ql Va .PARSEDIR
1063 are both set only while the
1064 .Ql Pa Makefiles
1065 are being parsed.
1066 If you want to retain their current values, assign them to a variable
1067 using assignment with expansion:
1068 .Pq Ql Cm \&:= .
1069 .It Va .PATH
1070 A variable that represents the list of directories that
1071 .Nm
1072 will search for files.
1073 The search list should be updated using the target
1074 .Ql Va .PATH
1075 rather than the variable.
1076 .It Ev PWD
1077 Alternate path to the current directory.
1078 .Nm
1079 normally sets
1080 .Ql Va .CURDIR
1081 to the canonical path given by
1082 .Xr getcwd 3 .
1083 However, if the environment variable
1084 .Ql Ev PWD
1085 is set and gives a path to the current directory, then
1086 .Nm
1087 sets
1088 .Ql Va .CURDIR
1089 to the value of
1090 .Ql Ev PWD
1091 instead.
1092 This behavior is disabled if
1093 .Ql Ev MAKEOBJDIRPREFIX
1094 is set or
1095 .Ql Ev MAKEOBJDIR
1096 contains a variable transform.
1097 .Ql Ev PWD
1098 is set to the value of
1099 .Ql Va .OBJDIR
1100 for all programs which
1101 .Nm
1102 executes.
1103 .It Ev .TARGETS
1104 The list of targets explicitly specified on the command line, if any.
1105 .It Ev VPATH
1106 Colon-separated
1107 .Pq Dq \&:
1108 lists of directories that
1109 .Nm
1110 will search for files.
1111 The variable is supported for compatibility with old make programs only,
1112 use
1113 .Ql Va .PATH
1114 instead.
1115 .El
1116 .Ss Variable modifiers
1117 Variable expansion may be modified to select or modify each word of the
1118 variable (where a
1119 .Dq word
1120 is white-space delimited sequence of characters).
1121 The general format of a variable expansion is as follows:
1122 .Pp
1123 .Dl ${variable[:modifier[:...]]}
1124 .Pp
1125 Each modifier begins with a colon,
1126 which may be escaped with a backslash
1127 .Pq Ql \e .
1128 .Pp
1129 A set of modifiers can be specified via a variable, as follows:
1130 .Pp
1131 .Dl modifier_variable=modifier[:...]
1132 .Dl ${variable:${modifier_variable}[:...]}
1133 .Pp
1134 In this case the first modifier in the modifier_variable does not
1135 start with a colon, since that must appear in the referencing
1136 variable.
1137 If any of the modifiers in the modifier_variable contain a dollar sign
1138 .Pq Ql $ ,
1139 these must be doubled to avoid early expansion.
1140 .Pp
1141 The supported modifiers are:
1142 .Bl -tag -width EEE
1143 .It Cm \&:E
1144 Replaces each word in the variable with its suffix.
1145 .It Cm \&:H
1146 Replaces each word in the variable with everything but the last component.
1147 .It Cm \&:M Ns Ar pattern
1148 Select only those words that match
1149 .Ar pattern .
1150 The standard shell wildcard characters
1151 .Pf ( Ql * ,
1152 .Ql \&? ,
1153 and
1154 .Ql Oo Oc )
1155 may
1156 be used.
1157 The wildcard characters may be escaped with a backslash
1158 .Pq Ql \e .
1159 As a consequence of the way values are split into words, matched,
1160 and then joined, a construct like
1161 .Dl ${VAR:M*}
1162 will normalize the inter-word spacing, removing all leading and
1163 trailing space, and converting multiple consecutive spaces
1164 to single spaces.
1165 .
1166 .It Cm \&:N Ns Ar pattern
1167 This is identical to
1168 .Ql Cm \&:M ,
1169 but selects all words which do not match
1170 .Ar pattern .
1171 .It Cm \&:O
1172 Order every word in variable alphabetically.
1173 To sort words in
1174 reverse order use the
1175 .Ql Cm \&:O:[-1..1]
1176 combination of modifiers.
1177 .It Cm \&:Ox
1178 Randomize words in variable.
1179 The results will be different each time you are referring to the
1180 modified variable; use the assignment with expansion
1181 .Pq Ql Cm \&:=
1182 to prevent such behavior.
1183 For example,
1184 .Bd -literal -offset indent
1185 LIST= uno due tre quattro
1186 RANDOM_LIST= ${LIST:Ox}
1187 STATIC_RANDOM_LIST:= ${LIST:Ox}
1189 all:
1190 @echo "${RANDOM_LIST}"
1191 @echo "${RANDOM_LIST}"
1192 @echo "${STATIC_RANDOM_LIST}"
1193 @echo "${STATIC_RANDOM_LIST}"
1194 .Ed
1195 may produce output similar to:
1196 .Bd -literal -offset indent
1197 quattro due tre uno
1198 tre due quattro uno
1199 due uno quattro tre
1200 due uno quattro tre
1201 .Ed
1202 .It Cm \&:Q
1203 Quotes every shell meta-character in the variable, so that it can be passed
1204 safely through recursive invocations of
1205 .Nm .
1206 .It Cm \&:R
1207 Replaces each word in the variable with everything but its suffix.
1208 .It Cm \&:gmtime
1209 The value is a format string for
1210 .Xr strftime 3 ,
1211 using the current
1212 .Xr gmtime 3 .
1213 .It Cm \&:hash
1214 Compute a 32-bit hash of the value and encode it as hex digits.
1215 .It Cm \&:localtime
1216 The value is a format string for
1217 .Xr strftime 3 ,
1218 using the current
1219 .Xr localtime 3 .
1220 .It Cm \&:tA
1221 Attempt to convert variable to an absolute path using
1222 .Xr realpath 3 ,
1223 if that fails, the value is unchanged.
1224 .It Cm \&:tl
1225 Converts variable to lower-case letters.
1226 .It Cm \&:ts Ns Ar c
1227 Words in the variable are normally separated by a space on expansion.
1228 This modifier sets the separator to the character
1229 .Ar c .
1230 If
1231 .Ar c
1232 is omitted, then no separator is used.
1233 The common escapes (including octal numeric codes), work as expected.
1234 .It Cm \&:tu
1235 Converts variable to upper-case letters.
1236 .It Cm \&:tW
1237 Causes the value to be treated as a single word
1238 (possibly containing embedded white space).
1239 See also
1240 .Ql Cm \&:[*] .
1241 .It Cm \&:tw
1242 Causes the value to be treated as a sequence of
1243 words delimited by white space.
1244 See also
1245 .Ql Cm \&:[@] .
1246 .Sm off
1247 .It Cm \&:S No \&/ Ar old_string No \&/ Ar new_string No \&/ Op Cm 1gW
1248 .Sm on
1249 Modify the first occurrence of
1250 .Ar old_string
1251 in the variable's value, replacing it with
1252 .Ar new_string .
1253 If a
1254 .Ql g
1255 is appended to the last slash of the pattern, all occurrences
1256 in each word are replaced.
1257 If a
1258 .Ql 1
1259 is appended to the last slash of the pattern, only the first word
1260 is affected.
1261 If a
1262 .Ql W
1263 is appended to the last slash of the pattern,
1264 then the value is treated as a single word
1265 (possibly containing embedded white space).
1266 If
1267 .Ar old_string
1268 begins with a caret
1269 .Pq Ql ^ ,
1270 .Ar old_string
1271 is anchored at the beginning of each word.
1272 If
1273 .Ar old_string
1274 ends with a dollar sign
1275 .Pq Ql \&$ ,
1276 it is anchored at the end of each word.
1277 Inside
1278 .Ar new_string ,
1279 an ampersand
1280 .Pq Ql \*[Am]
1281 is replaced by
1282 .Ar old_string
1283 (without any
1284 .Ql ^
1285 or
1286 .Ql \&$ ) .
1287 Any character may be used as a delimiter for the parts of the modifier
1288 string.
1289 The anchoring, ampersand and delimiter characters may be escaped with a
1290 backslash
1291 .Pq Ql \e .
1292 .Pp
1293 Variable expansion occurs in the normal fashion inside both
1294 .Ar old_string
1295 and
1296 .Ar new_string
1297 with the single exception that a backslash is used to prevent the expansion
1298 of a dollar sign
1299 .Pq Ql \&$ ,
1300 not a preceding dollar sign as is usual.
1301 .Sm off
1302 .It Cm \&:C No \&/ Ar pattern No \&/ Ar replacement No \&/ Op Cm 1gW
1303 .Sm on
1304 The
1305 .Cm \&:C
1306 modifier is just like the
1307 .Cm \&:S
1308 modifier except that the old and new strings, instead of being
1309 simple strings, are an extended regular expression (see
1310 .Xr regex 3 )
1311 string
1312 .Ar pattern
1313 and an
1314 .Xr ed 1 Ns \-style
1315 string
1316 .Ar replacement .
1317 Normally, the first occurrence of the pattern
1318 .Ar pattern
1319 in each word of the value is substituted with
1320 .Ar replacement .
1321 The
1322 .Ql 1
1323 modifier causes the substitution to apply to at most one word; the
1324 .Ql g
1325 modifier causes the substitution to apply to as many instances of the
1326 search pattern
1327 .Ar pattern
1328 as occur in the word or words it is found in; the
1329 .Ql W
1330 modifier causes the value to be treated as a single word
1331 (possibly containing embedded white space).
1332 Note that
1333 .Ql 1
1334 and
1335 .Ql g
1336 are orthogonal; the former specifies whether multiple words are
1337 potentially affected, the latter whether multiple substitutions can
1338 potentially occur within each affected word.
1339 .Pp
1340 As for the
1341 .Cm \&:S
1342 modifier, the
1343 .Ar pattern
1344 and
1345 .Ar replacement
1346 are subjected to variable expansion before being parsed as
1347 regular expressions.
1348 .It Cm \&:T
1349 Replaces each word in the variable with its last component.
1350 .It Cm \&:u
1351 Remove adjacent duplicate words (like
1352 .Xr uniq 1 ) .
1353 .Sm off
1354 .It Cm \&:\&? Ar true_string Cm \&: Ar false_string
1355 .Sm on
1356 If the variable name (not its value), when parsed as a .if conditional
1357 expression, evaluates to true, return as its value the
1358 .Ar true_string ,
1359 otherwise return the
1360 .Ar false_string .
1361 Since the variable name is used as the expression, \&:\&? must be the
1362 first modifier after the variable name itself - which will, of course,
1363 usually contain variable expansions.
1364 A common error is trying to use expressions like
1365 .Dl ${NUMBERS:M42:?match:no}
1366 which actually tests defined(NUMBERS),
1367 to determine is any words match "42" you need to use something like:
1368 .Dl ${"${NUMBERS:M42}" != \&"\&":?match:no} .
1369 .It Ar :old_string=new_string
1370 This is the
1371 .At V
1372 style variable substitution.
1373 It must be the last modifier specified.
1374 If
1375 .Ar old_string
1376 or
1377 .Ar new_string
1378 do not contain the pattern matching character
1379 .Ar %
1380 then it is assumed that they are
1381 anchored at the end of each word, so only suffixes or entire
1382 words may be replaced.
1383 Otherwise
1384 .Ar %
1385 is the substring of
1386 .Ar old_string
1387 to be replaced in
1388 .Ar new_string .
1389 .Pp
1390 Variable expansion occurs in the normal fashion inside both
1391 .Ar old_string
1392 and
1393 .Ar new_string
1394 with the single exception that a backslash is used to prevent the
1395 expansion of a dollar sign
1396 .Pq Ql \&$ ,
1397 not a preceding dollar sign as is usual.
1398 .Sm off
1399 .It Cm \&:@ Ar temp Cm @ Ar string Cm @
1400 .Sm on
1401 This is the loop expansion mechanism from the OSF Development
1402 Environment (ODE) make.
1403 Unlike
1404 .Cm \&.for
1405 loops expansion occurs at the time of
1406 reference.
1407 Assign
1408 .Ar temp
1409 to each word in the variable and evaluate
1410 .Ar string .
1411 The ODE convention is that
1412 .Ar temp
1413 should start and end with a period.
1414 For example.
1415 .Dl ${LINKS:@.LINK.@${LN} ${TARGET} ${.LINK.}@}
1416 .Pp
1417 However a single character variable is often more readable:
1418 .Dl ${MAKE_PRINT_VAR_ON_ERROR:@v@$v='${$v}'${.newline}@}
1419 .It Cm \&:U Ns Ar newval
1420 If the variable is undefined
1421 .Ar newval
1422 is the value.
1423 If the variable is defined, the existing value is returned.
1424 This is another ODE make feature.
1425 It is handy for setting per-target CFLAGS for instance:
1426 .Dl ${_${.TARGET:T}_CFLAGS:U${DEF_CFLAGS}}
1427 If a value is only required if the variable is undefined, use:
1428 .Dl ${VAR:D:Unewval}
1429 .It Cm \&:D Ns Ar newval
1430 If the variable is defined
1431 .Ar newval
1432 is the value.
1433 .It Cm \&:L
1434 The name of the variable is the value.
1435 .It Cm \&:P
1436 The path of the node which has the same name as the variable
1437 is the value.
1438 If no such node exists or its path is null, then the
1439 name of the variable is used.
1440 In order for this modifier to work, the name (node) must at least have
1441 appeared on the rhs of a dependency.
1442 .Sm off
1443 .It Cm \&:\&! Ar cmd Cm \&!
1444 .Sm on
1445 The output of running
1446 .Ar cmd
1447 is the value.
1448 .It Cm \&:sh
1449 If the variable is non-empty it is run as a command and the output
1450 becomes the new value.
1451 .It Cm \&::= Ns Ar str
1452 The variable is assigned the value
1453 .Ar str
1454 after substitution.
1455 This modifier and its variations are useful in
1456 obscure situations such as wanting to set a variable when shell commands
1457 are being parsed.
1458 These assignment modifiers always expand to
1459 nothing, so if appearing in a rule line by themselves should be
1460 preceded with something to keep
1461 .Nm
1462 happy.
1463 .Pp
1464 The
1465 .Ql Cm \&::
1466 helps avoid false matches with the
1467 .At V
1468 style
1469 .Cm \&:=
1470 modifier and since substitution always occurs the
1471 .Cm \&::=
1472 form is vaguely appropriate.
1473 .It Cm \&::?= Ns Ar str
1474 As for
1475 .Cm \&::=
1476 but only if the variable does not already have a value.
1477 .It Cm \&::+= Ns Ar str
1478 Append
1479 .Ar str
1480 to the variable.
1481 .It Cm \&::!= Ns Ar cmd
1482 Assign the output of
1483 .Ar cmd
1484 to the variable.
1485 .It Cm \&:\&[ Ns Ar range Ns Cm \&]
1486 Selects one or more words from the value,
1487 or performs other operations related to the way in which the
1488 value is divided into words.
1489 .Pp
1490 Ordinarily, a value is treated as a sequence of words
1491 delimited by white space.
1492 Some modifiers suppress this behavior,
1493 causing a value to be treated as a single word
1494 (possibly containing embedded white space).
1495 An empty value, or a value that consists entirely of white-space,
1496 is treated as a single word.
1497 For the purposes of the
1498 .Ql Cm \&:[]
1499 modifier, the words are indexed both forwards using positive integers
1500 (where index 1 represents the first word),
1501 and backwards using negative integers
1502 (where index \-1 represents the last word).
1503 .Pp
1504 The
1505 .Ar range
1506 is subjected to variable expansion, and the expanded result is
1507 then interpreted as follows:
1508 .Bl -tag -width index
1509 .\" :[n]
1510 .It Ar index
1511 Selects a single word from the value.
1512 .\" :[start..end]
1513 .It Ar start Ns Cm \&.. Ns Ar end
1514 Selects all words from
1515 .Ar start
1516 to
1517 .Ar end ,
1518 inclusive.
1519 For example,
1520 .Ql Cm \&:[2..-1]
1521 selects all words from the second word to the last word.
1522 If
1523 .Ar start
1524 is greater than
1525 .Ar end ,
1526 then the words are output in reverse order.
1527 For example,
1528 .Ql Cm \&:[-1..1]
1529 selects all the words from last to first.
1530 .\" :[*]
1531 .It Cm \&*
1532 Causes subsequent modifiers to treat the value as a single word
1533 (possibly containing embedded white space).
1534 Analogous to the effect of
1535 \&"$*\&"
1536 in Bourne shell.
1537 .\" :[0]
1538 .It 0
1539 Means the same as
1540 .Ql Cm \&:[*] .
1541 .\" :[*]
1542 .It Cm \&@
1543 Causes subsequent modifiers to treat the value as a sequence of words
1544 delimited by white space.
1545 Analogous to the effect of
1546 \&"$@\&"
1547 in Bourne shell.
1548 .\" :[#]
1549 .It Cm \&#
1550 Returns the number of words in the value.
1551 .El \" :[range]
1552 .El
1553 .Sh INCLUDE STATEMENTS, CONDITIONALS AND FOR LOOPS
1554 Makefile inclusion, conditional structures and for loops reminiscent
1555 of the C programming language are provided in
1556 .Nm .
1557 All such structures are identified by a line beginning with a single
1558 dot
1559 .Pq Ql \&.
1560 character.
1561 Files are included with either
1562 .Cm \&.include Aq Ar file
1563 or
1564 .Cm \&.include Pf \*q Ar file Ns \*q .
1565 Variables between the angle brackets or double quotes are expanded
1566 to form the file name.
1567 If angle brackets are used, the included makefile is expected to be in
1568 the system makefile directory.
1569 If double quotes are used, the including makefile's directory and any
1570 directories specified using the
1571 .Fl I
1572 option are searched before the system
1573 makefile directory.
1574 For compatibility with other versions of
1575 .Nm
1576 .Ql include file ...
1577 is also accepted.
1578 .Pp
1579 If the include statement is written as
1580 .Cm .-include
1581 or as
1582 .Cm .sinclude
1583 then errors locating and/or opening include files are ignored.
1584 .Pp
1585 If the include statement is written as
1586 .Cm .dinclude
1587 not only are errors locating and/or opening include files ignored,
1588 but stale dependencies within the included file will be ignored
1589 just like
1590 .Va .MAKE.DEPENDFILE .
1591 .Pp
1592 Conditional expressions are also preceded by a single dot as the first
1593 character of a line.
1594 The possible conditionals are as follows:
1595 .Bl -tag -width Ds
1596 .It Ic .error Ar message
1597 The message is printed along with the name of the makefile and line number,
1598 then
1599 .Nm
1600 will exit.
1601 .It Ic .export Ar variable ...
1602 Export the specified global variable.
1603 If no variable list is provided, all globals are exported
1604 except for internal variables (those that start with
1605 .Ql \&. ) .
1606 This is not affected by the
1607 .Fl X
1608 flag, so should be used with caution.
1609 For compatibility with other
1610 .Nm
1611 programs
1612 .Ql export variable=value
1613 is also accepted.
1614 .Pp
1615 Appending a variable name to
1616 .Va .MAKE.EXPORTED
1617 is equivalent to exporting a variable.
1618 .It Ic .export-env Ar variable ...
1619 The same as
1620 .Ql .export ,
1621 except that the variable is not appended to
1622 .Va .MAKE.EXPORTED .
1623 This allows exporting a value to the environment which is different from that
1624 used by
1625 .Nm
1626 internally.
1627 .It Ic .export-literal Ar variable ...
1628 The same as
1629 .Ql .export-env ,
1630 except that variables in the value are not expanded.
1631 .It Ic .info Ar message
1632 The message is printed along with the name of the makefile and line number.
1633 .It Ic .undef Ar variable
1634 Un-define the specified global variable.
1635 Only global variables may be un-defined.
1636 .It Ic .unexport Ar variable ...
1637 The opposite of
1638 .Ql .export .
1639 The specified global
1640 .Va variable
1641 will be removed from
1642 .Va .MAKE.EXPORTED .
1643 If no variable list is provided, all globals are unexported,
1644 and
1645 .Va .MAKE.EXPORTED
1646 deleted.
1647 .It Ic .unexport-env
1648 Unexport all globals previously exported and
1649 clear the environment inherited from the parent.
1650 This operation will cause a memory leak of the original environment,
1651 so should be used sparingly.
1652 Testing for
1653 .Va .MAKE.LEVEL
1654 being 0, would make sense.
1655 Also note that any variables which originated in the parent environment
1656 should be explicitly preserved if desired.
1657 For example:
1658 .Bd -literal -offset indent
1659 .Li .if ${.MAKE.LEVEL} == 0
1660 PATH := ${PATH}
1661 .Li .unexport-env
1662 .Li .export PATH
1663 .Li .endif
1664 .Pp
1665 .Ed
1666 Would result in an environment containing only
1667 .Ql Ev PATH ,
1668 which is the minimal useful environment.
1669 Actually
1670 .Ql Ev .MAKE.LEVEL
1671 will also be pushed into the new environment.
1672 .It Ic .warning Ar message
1673 The message prefixed by
1674 .Ql Pa warning:
1675 is printed along with the name of the makefile and line number.
1676 .It Ic \&.if Oo \&! Oc Ns Ar expression Op Ar operator expression ...
1677 Test the value of an expression.
1678 .It Ic .ifdef Oo \&! Oc Ns Ar variable Op Ar operator variable ...
1679 Test the value of a variable.
1680 .It Ic .ifndef Oo \&! Oc Ns Ar variable Op Ar operator variable ...
1681 Test the value of a variable.
1682 .It Ic .ifmake Oo \&! Oc Ns Ar target Op Ar operator target ...
1683 Test the target being built.
1684 .It Ic .ifnmake Oo \&! Ns Oc Ar target Op Ar operator target ...
1685 Test the target being built.
1686 .It Ic .else
1687 Reverse the sense of the last conditional.
1688 .It Ic .elif Oo \&! Ns Oc Ar expression Op Ar operator expression ...
1689 A combination of
1690 .Ql Ic .else
1691 followed by
1692 .Ql Ic .if .
1693 .It Ic .elifdef Oo \&! Oc Ns Ar variable Op Ar operator variable ...
1694 A combination of
1695 .Ql Ic .else
1696 followed by
1697 .Ql Ic .ifdef .
1698 .It Ic .elifndef Oo \&! Oc Ns Ar variable Op Ar operator variable ...
1699 A combination of
1700 .Ql Ic .else
1701 followed by
1702 .Ql Ic .ifndef .
1703 .It Ic .elifmake Oo \&! Oc Ns Ar target Op Ar operator target ...
1704 A combination of
1705 .Ql Ic .else
1706 followed by
1707 .Ql Ic .ifmake .
1708 .It Ic .elifnmake Oo \&! Oc Ns Ar target Op Ar operator target ...
1709 A combination of
1710 .Ql Ic .else
1711 followed by
1712 .Ql Ic .ifnmake .
1713 .It Ic .endif
1714 End the body of the conditional.
1715 .El
1716 .Pp
1717 The
1718 .Ar operator
1719 may be any one of the following:
1720 .Bl -tag -width "Cm XX"
1721 .It Cm \&|\&|
1722 Logical OR.
1723 .It Cm \&\*[Am]\*[Am]
1724 Logical
1725 .Tn AND ;
1726 of higher precedence than
1727 .Dq \&|\&| .
1728 .El
1729 .Pp
1730 As in C,
1731 .Nm
1732 will only evaluate a conditional as far as is necessary to determine
1733 its value.
1734 Parentheses may be used to change the order of evaluation.
1735 The boolean operator
1736 .Ql Ic \&!
1737 may be used to logically negate an entire
1738 conditional.
1739 It is of higher precedence than
1740 .Ql Ic \&\*[Am]\*[Am] .
1741 .Pp
1742 The value of
1743 .Ar expression
1744 may be any of the following:
1745 .Bl -tag -width defined
1746 .It Ic defined
1747 Takes a variable name as an argument and evaluates to true if the variable
1748 has been defined.
1749 .It Ic make
1750 Takes a target name as an argument and evaluates to true if the target
1751 was specified as part of
1752 .Nm Ns 's
1753 command line or was declared the default target (either implicitly or
1754 explicitly, see
1755 .Va .MAIN )
1756 before the line containing the conditional.
1757 .It Ic empty
1758 Takes a variable, with possible modifiers, and evaluates to true if
1759 the expansion of the variable would result in an empty string.
1760 .It Ic exists
1761 Takes a file name as an argument and evaluates to true if the file exists.
1762 The file is searched for on the system search path (see
1763 .Va .PATH ) .
1764 .It Ic target
1765 Takes a target name as an argument and evaluates to true if the target
1766 has been defined.
1767 .It Ic commands
1768 Takes a target name as an argument and evaluates to true if the target
1769 has been defined and has commands associated with it.
1770 .El
1771 .Pp
1772 .Ar Expression
1773 may also be an arithmetic or string comparison.
1774 Variable expansion is
1775 performed on both sides of the comparison, after which the integral
1776 values are compared.
1777 A value is interpreted as hexadecimal if it is
1778 preceded by 0x, otherwise it is decimal; octal numbers are not supported.
1779 The standard C relational operators are all supported.
1780 If after
1781 variable expansion, either the left or right hand side of a
1782 .Ql Ic ==
1783 or
1784 .Ql Ic "!="
1785 operator is not an integral value, then
1786 string comparison is performed between the expanded
1787 variables.
1788 If no relational operator is given, it is assumed that the expanded
1789 variable is being compared against 0 or an empty string in the case
1790 of a string comparison.
1791 .Pp
1792 When
1793 .Nm
1794 is evaluating one of these conditional expressions, and it encounters
1795 a (white-space separated) word it doesn't recognize, either the
1796 .Dq make
1797 or
1798 .Dq defined
1799 expression is applied to it, depending on the form of the conditional.
1800 If the form is
1801 .Ql Ic .ifdef ,
1802 .Ql Ic .ifndef ,
1803 or
1804 .Ql Ic .if
1805 the
1806 .Dq defined
1807 expression is applied.
1808 Similarly, if the form is
1809 .Ql Ic .ifmake
1810 or
1811 .Ql Ic .ifnmake , the
1812 .Dq make
1813 expression is applied.
1814 .Pp
1815 If the conditional evaluates to true the parsing of the makefile continues
1816 as before.
1817 If it evaluates to false, the following lines are skipped.
1818 In both cases this continues until a
1819 .Ql Ic .else
1820 or
1821 .Ql Ic .endif
1822 is found.
1823 .Pp
1824 For loops are typically used to apply a set of rules to a list of files.
1825 The syntax of a for loop is:
1826 .Pp
1827 .Bl -tag -compact -width Ds
1828 .It Ic \&.for Ar variable Oo Ar variable ... Oc Ic in Ar expression
1829 .It Aq make-rules
1830 .It Ic \&.endfor
1831 .El
1832 .Pp
1833 After the for
1834 .Ic expression
1835 is evaluated, it is split into words.
1836 On each iteration of the loop, one word is taken and assigned to each
1837 .Ic variable ,
1838 in order, and these
1839 .Ic variables
1840 are substituted into the
1841 .Ic make-rules
1842 inside the body of the for loop.
1843 The number of words must come out even; that is, if there are three
1844 iteration variables, the number of words provided must be a multiple
1845 of three.
1846 .Sh COMMENTS
1847 Comments begin with a hash
1848 .Pq Ql \&#
1849 character, anywhere but in a shell
1850 command line, and continue to the end of an unescaped new line.
1851 .Sh SPECIAL SOURCES (ATTRIBUTES)
1852 .Bl -tag -width .IGNOREx
1853 .It Ic .EXEC
1854 Target is never out of date, but always execute commands anyway.
1855 .It Ic .IGNORE
1856 Ignore any errors from the commands associated with this target, exactly
1857 as if they all were preceded by a dash
1858 .Pq Ql \- .
1859 .\" .It Ic .INVISIBLE
1860 .\" XXX
1861 .\" .It Ic .JOIN
1862 .\" XXX
1863 .It Ic .MADE
1864 Mark all sources of this target as being up-to-date.
1865 .It Ic .MAKE
1866 Execute the commands associated with this target even if the
1867 .Fl n
1868 or
1869 .Fl t
1870 options were specified.
1871 Normally used to mark recursive
1872 .Nm Ns s .
1873 .It Ic .META
1874 Create a meta file for the target, even if it is flagged as
1875 .Ic .PHONY ,
1876 .Ic .MAKE ,
1877 or
1878 .Ic .SPECIAL .
1879 Usage in conjunction with
1880 .Ic .MAKE
1881 is the most likely case.
1882 In "meta" mode, the target is out-of-date if the meta file is missing.
1883 .It Ic .NOMETA
1884 Do not create a meta file for the target.
1885 Meta files are also not created for
1886 .Ic .PHONY ,
1887 .Ic .MAKE ,
1888 or
1889 .Ic .SPECIAL
1890 targets.
1891 .It Ic .NOMETA_CMP
1892 Ignore differences in commands when deciding if target is out of date.
1893 This is useful if the command contains a value which always changes.
1894 If the number of commands change, though, the target will still be out of date.
1895 The same effect applies to any command line that uses the variable
1896 .Va .OODATE ,
1897 which can be used for that purpose even when not otherwise needed or desired:
1898 .Bd -literal -offset indent
1900 skip-compare-for-some:
1901 @echo this will be compared
1902 @echo this will not ${.OODATE:M.NOMETA_CMP}
1903 @echo this will also be compared
1905 .Ed
1906 The
1907 .Cm \&:M
1908 pattern suppresses any expansion of the unwanted variable.
1909 .It Ic .NOPATH
1910 Do not search for the target in the directories specified by
1911 .Ic .PATH .
1912 .It Ic .NOTMAIN
1913 Normally
1914 .Nm
1915 selects the first target it encounters as the default target to be built
1916 if no target was specified.
1917 This source prevents this target from being selected.
1918 .It Ic .OPTIONAL
1919 If a target is marked with this attribute and
1920 .Nm
1921 can't figure out how to create it, it will ignore this fact and assume
1922 the file isn't needed or already exists.
1923 .It Ic .PHONY
1924 The target does not
1925 correspond to an actual file; it is always considered to be out of date,
1926 and will not be created with the
1927 .Fl t
1928 option.
1929 Suffix-transformation rules are not applied to
1930 .Ic .PHONY
1931 targets.
1932 .It Ic .PRECIOUS
1933 When
1934 .Nm
1935 is interrupted, it normally removes any partially made targets.
1936 This source prevents the target from being removed.
1937 .It Ic .RECURSIVE
1938 Synonym for
1939 .Ic .MAKE .
1940 .It Ic .SILENT
1941 Do not echo any of the commands associated with this target, exactly
1942 as if they all were preceded by an at sign
1943 .Pq Ql @ .
1944 .It Ic .USE
1945 Turn the target into
1946 .Nm Ns 's
1947 version of a macro.
1948 When the target is used as a source for another target, the other target
1949 acquires the commands, sources, and attributes (except for
1950 .Ic .USE )
1951 of the
1952 source.
1953 If the target already has commands, the
1954 .Ic .USE
1955 target's commands are appended
1956 to them.
1957 .It Ic .USEBEFORE
1958 Exactly like
1959 .Ic .USE ,
1960 but prepend the
1961 .Ic .USEBEFORE
1962 target commands to the target.
1963 .It Ic .WAIT
1964 If
1965 .Ic .WAIT
1966 appears in a dependency line, the sources that precede it are
1967 made before the sources that succeed it in the line.
1968 Since the dependents of files are not made until the file itself
1969 could be made, this also stops the dependents being built unless they
1970 are needed for another branch of the dependency tree.
1971 So given:
1972 .Bd -literal
1973 x: a .WAIT b
1974 echo x
1975 a:
1976 echo a
1977 b: b1
1978 echo b
1979 b1:
1980 echo b1
1982 .Ed
1983 the output is always
1984 .Ql a ,
1985 .Ql b1 ,
1986 .Ql b ,
1987 .Ql x .
1988 .br
1989 The ordering imposed by
1990 .Ic .WAIT
1991 is only relevant for parallel makes.
1992 .El
1993 .Sh SPECIAL TARGETS
1994 Special targets may not be included with other targets, i.e. they must be
1995 the only target specified.
1996 .Bl -tag -width .BEGINx
1997 .It Ic .BEGIN
1998 Any command lines attached to this target are executed before anything
1999 else is done.
2000 .It Ic .DEFAULT
2001 This is sort of a
2002 .Ic .USE
2003 rule for any target (that was used only as a
2004 source) that
2005 .Nm
2006 can't figure out any other way to create.
2007 Only the shell script is used.
2008 The
2009 .Ic .IMPSRC
2010 variable of a target that inherits
2011 .Ic .DEFAULT Ns 's
2012 commands is set
2013 to the target's own name.
2014 .It Ic .END
2015 Any command lines attached to this target are executed after everything
2016 else is done.
2017 .It Ic .ERROR
2018 Any command lines attached to this target are executed when another target fails.
2019 The
2020 .Ic .ERROR_TARGET
2021 variable is set to the target that failed.
2022 See also
2023 .Ic MAKE_PRINT_VAR_ON_ERROR .
2024 .It Ic .IGNORE
2025 Mark each of the sources with the
2026 .Ic .IGNORE
2027 attribute.
2028 If no sources are specified, this is the equivalent of specifying the
2029 .Fl i
2030 option.
2031 .It Ic .INTERRUPT
2032 If
2033 .Nm
2034 is interrupted, the commands for this target will be executed.
2035 .It Ic .MAIN
2036 If no target is specified when
2037 .Nm
2038 is invoked, this target will be built.
2039 .It Ic .MAKEFLAGS
2040 This target provides a way to specify flags for
2041 .Nm
2042 when the makefile is used.
2043 The flags are as if typed to the shell, though the
2044 .Fl f
2045 option will have
2046 no effect.
2047 .\" XXX: NOT YET!!!!
2048 .\" .It Ic .NOTPARALLEL
2049 .\" The named targets are executed in non parallel mode.
2050 .\" If no targets are
2051 .\" specified, then all targets are executed in non parallel mode.
2052 .It Ic .NOPATH
2053 Apply the
2054 .Ic .NOPATH
2055 attribute to any specified sources.
2056 .It Ic .NOTPARALLEL
2057 Disable parallel mode.
2058 .It Ic .NO_PARALLEL
2059 Synonym for
2060 .Ic .NOTPARALLEL ,
2061 for compatibility with other pmake variants.
2062 .It Ic .OBJDIR
2063 The source is a new value for
2064 .Ql Va .OBJDIR .
2065 If it exists,
2066 .Nm
2067 will
2068 .Xr chdir 2
2069 to it and update the value of
2070 .Ql Va .OBJDIR .
2071 .It Ic .ORDER
2072 The named targets are made in sequence.
2073 This ordering does not add targets to the list of targets to be made.
2074 Since the dependents of a target do not get built until the target itself
2075 could be built, unless
2076 .Ql a
2077 is built by another part of the dependency graph,
2078 the following is a dependency loop:
2079 .Bd -literal
2080 \&.ORDER: b a
2081 b: a
2082 .Ed
2083 .Pp
2084 The ordering imposed by
2085 .Ic .ORDER
2086 is only relevant for parallel makes.
2087 .\" XXX: NOT YET!!!!
2088 .\" .It Ic .PARALLEL
2089 .\" The named targets are executed in parallel mode.
2090 .\" If no targets are
2091 .\" specified, then all targets are executed in parallel mode.
2092 .It Ic .PATH
2093 The sources are directories which are to be searched for files not
2094 found in the current directory.
2095 If no sources are specified, any previously specified directories are
2096 deleted.
2097 If the source is the special
2098 .Ic .DOTLAST
2099 target, then the current working
2100 directory is searched last.
2101 .It Ic .PATH. Ns Va suffix
2102 Like
2103 .Ic .PATH
2104 but applies only to files with a particular suffix.
2105 The suffix must have been previously declared with
2106 .Ic .SUFFIXES .
2107 .It Ic .PHONY
2108 Apply the
2109 .Ic .PHONY
2110 attribute to any specified sources.
2111 .It Ic .PRECIOUS
2112 Apply the
2113 .Ic .PRECIOUS
2114 attribute to any specified sources.
2115 If no sources are specified, the
2116 .Ic .PRECIOUS
2117 attribute is applied to every
2118 target in the file.
2119 .It Ic .SHELL
2120 Sets the shell that
2121 .Nm
2122 will use to execute commands.
2123 The sources are a set of
2124 .Ar field=value
2125 pairs.
2126 .Bl -tag -width hasErrCtls
2127 .It Ar name
2128 This is the minimal specification, used to select one of the built-in
2129 shell specs;
2130 .Ar sh ,
2131 .Ar ksh ,
2132 and
2133 .Ar csh .
2134 .It Ar path
2135 Specifies the path to the shell.
2136 .It Ar hasErrCtl
2137 Indicates whether the shell supports exit on error.
2138 .It Ar check
2139 The command to turn on error checking.
2140 .It Ar ignore
2141 The command to disable error checking.
2142 .It Ar echo
2143 The command to turn on echoing of commands executed.
2144 .It Ar quiet
2145 The command to turn off echoing of commands executed.
2146 .It Ar filter
2147 The output to filter after issuing the
2148 .Ar quiet
2149 command.
2150 It is typically identical to
2151 .Ar quiet .
2152 .It Ar errFlag
2153 The flag to pass the shell to enable error checking.
2154 .It Ar echoFlag
2155 The flag to pass the shell to enable command echoing.
2156 .It Ar newline
2157 The string literal to pass the shell that results in a single newline
2158 character when used outside of any quoting characters.
2159 .El
2160 Example:
2161 .Bd -literal
2162 \&.SHELL: name=ksh path=/bin/ksh hasErrCtl=true \e
2163 check="set \-e" ignore="set +e" \e
2164 echo="set \-v" quiet="set +v" filter="set +v" \e
2165 echoFlag=v errFlag=e newline="'\en'"
2166 .Ed
2167 .It Ic .SILENT
2168 Apply the
2169 .Ic .SILENT
2170 attribute to any specified sources.
2171 If no sources are specified, the
2172 .Ic .SILENT
2173 attribute is applied to every
2174 command in the file.
2175 .It Ic .STALE
2176 This target gets run when a dependency file contains stale entries, having
2177 .Va .ALLSRC
2178 set to the name of that dependency file.
2179 .It Ic .SUFFIXES
2180 Each source specifies a suffix to
2181 .Nm .
2182 If no sources are specified, any previously specified suffixes are deleted.
2183 It allows the creation of suffix-transformation rules.
2184 .Pp
2185 Example:
2186 .Bd -literal
2187 \&.SUFFIXES: .o
2188 \&.c.o:
2189 cc \-o ${.TARGET} \-c ${.IMPSRC}
2190 .Ed
2191 .El
2192 .Sh ENVIRONMENT
2193 .Nm
2194 uses the following environment variables, if they exist:
2195 .Ev MACHINE ,
2196 .Ev MACHINE_ARCH ,
2197 .Ev MAKE ,
2198 .Ev MAKEFLAGS ,
2199 .Ev MAKEOBJDIR ,
2200 .Ev MAKEOBJDIRPREFIX ,
2201 .Ev MAKESYSPATH ,
2202 .Ev PWD ,
2203 and
2204 .Ev TMPDIR .
2205 .Pp
2206 .Ev MAKEOBJDIRPREFIX
2207 and
2208 .Ev MAKEOBJDIR
2209 may only be set in the environment or on the command line to
2210 .Nm
2211 and not as makefile variables;
2212 see the description of
2213 .Ql Va .OBJDIR
2214 for more details.
2215 .Sh FILES
2216 .Bl -tag -width /usr/share/mk -compact
2217 .It .depend
2218 list of dependencies
2219 .It Makefile
2220 list of dependencies
2221 .It makefile
2222 list of dependencies
2223 .It sys.mk
2224 system makefile
2225 .It /usr/share/mk
2226 system makefile directory
2227 .El
2228 .Sh COMPATIBILITY
2229 The basic make syntax is compatible between different versions of make;
2230 however the special variables, variable modifiers and conditionals are not.
2231 .Ss Older versions
2232 An incomplete list of changes in older versions of
2233 .Nm :
2234 .Pp
2235 The way that .for loop variables are substituted changed after
2236 .Nx 5.0
2237 so that they still appear to be variable expansions.
2238 In particular this stops them being treated as syntax, and removes some
2239 obscure problems using them in .if statements.
2240 .Pp
2241 The way that parallel makes are scheduled changed in
2242 .Nx 4.0
2243 so that .ORDER and .WAIT apply recursively to the dependent nodes.
2244 The algorithms used may change again in the future.
2245 .Ss Other make dialects
2246 Other make dialects (GNU make, SVR4 make, POSIX make, etc.) do not
2247 support most of the features of
2248 .Nm
2249 as described in this manual.
2250 Most notably:
2251 .Bl -bullet -offset indent
2252 .It
2253 The
2254 .Ic .WAIT
2255 and
2256 .Ic .ORDER
2257 declarations and most functionality pertaining to parallelization.
2258 (GNU make supports parallelization but lacks these features needed to
2259 control it effectively.)
2260 .It
2261 Directives, including for loops and conditionals and most of the
2262 forms of include files.
2263 (GNU make has its own incompatible and less powerful syntax for
2264 conditionals.)
2265 .It
2266 All built-in variables that begin with a dot.
2267 .It
2268 Most of the special sources and targets that begin with a dot,
2269 with the notable exception of
2270 .Ic .PHONY ,
2271 .Ic .PRECIOUS ,
2272 and
2273 .Ic .SUFFIXES .
2274 .It
2275 Variable modifiers, except for the
2276 .Dl :old=new
2277 string substitution, which does not portably support globbing with
2278 .Ql %
2279 and historically only works on declared suffixes.
2280 .It
2281 The
2282 .Ic $>
2283 variable even in its short form; most makes support this functionality
2284 but its name varies.
2285 .El
2286 .Pp
2287 Some features are somewhat more portable, such as assignment with
2288 .Ic += ,
2289 .Ic ?= ,
2290 and
2291 .Ic != .
2292 The
2293 .Ic .PATH
2294 functionality is based on an older feature
2295 .Ic VPATH
2296 found in GNU make and many versions of SVR4 make; however,
2297 historically its behavior is too ill-defined (and too buggy) to rely
2298 upon.
2299 .Pp
2300 The
2301 .Ic $@
2302 and
2303 .Ic $<
2304 variables are more or less universally portable, as is the
2305 .Ic $(MAKE)
2306 variable.
2307 Basic use of suffix rules (for files only in the current directory,
2308 not trying to chain transformations together, etc.) is also reasonably
2309 portable.
2310 .Sh SEE ALSO
2311 .Xr mkdep 1
2312 .Sh HISTORY
2313 A
2314 .Nm
2315 command appeared in
2316 .At v7 .
2317 This
2318 .Nm
2319 implementation is based on Adam De Boor's pmake program which was written
2320 for Sprite at Berkeley.
2321 It was designed to be a parallel distributed make running jobs on different
2322 machines using a daemon called
2323 .Dq customs .
2324 .Pp
2325 Historically the target/dependency
2326 .Dq FRC
2327 has been used to FoRCe rebuilding (since the target/dependency
2328 does not exist... unless someone creates an
2329 .Dq FRC
2330 file).
2331 .Sh BUGS
2332 The
2333 .Nm
2334 syntax is difficult to parse without actually acting of the data.
2335 For instance finding the end of a variable use should involve scanning each
2336 the modifiers using the correct terminator for each field.
2337 In many places
2338 .Nm
2339 just counts {} and () in order to find the end of a variable expansion.
2340 .Pp
2341 There is no way of escaping a space character in a filename.