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mk.1 (14216B)
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1 .TH MK 1
2 .SH NAME
3 mk \- maintain (make) related files
4 .SH SYNOPSIS
5 .B mk
6 [
7 .B -f
8 .I mkfile
9 ] ...
10 [
11 .I option ...
12 ]
13 [
14 .I target ...
15 ]
16 .SH DESCRIPTION
17 .I Mk
18 uses the dependency rules specified in
19 .I mkfile
20 to control the update (usually by compilation) of
21 .I targets
22 (usually files)
23 from the source files upon which they depend.
24 The
25 .I mkfile
26 (default
27 .LR mkfile )
28 contains a
29 .I rule
30 for each target that identifies the files and other
31 targets upon which it depends and an
32 .IR sh (1)
33 script, a
34 .IR recipe ,
35 to update the target.
36 The script is run if the target does not exist
37 or if it is older than any of the files it depends on.
38 .I Mkfile
39 may also contain
40 .I meta-rules
41 that define actions for updating implicit targets.
42 If no
43 .I target
44 is specified, the target of the first rule (not meta-rule) in
45 .I mkfile
46 is updated.
47 .PP
48 The environment variable
49 .B $NPROC
50 determines how many targets may be updated simultaneously;
51 Some operating systems, e.g., Plan 9, set
52 .B $NPROC
53 automatically to the number of CPUs on the current machine.
54 .PP
55 Options are:
56 .TP \w'\fL-d[egp]\ 'u
57 .B -a
58 Assume all targets to be out of date.
59 Thus, everything is updated.
60 .PD 0
61 .TP
62 .BR -d [ egp ]
63 Produce debugging output
64 .RB ( p
65 is for parsing,
66 .B g
67 for graph building,
68 .B e
69 for execution).
70 .TP
71 .B -e
72 Explain why each target is made.
73 .TP
74 .B -i
75 Force any missing intermediate targets to be made.
76 .TP
77 .B -k
78 Do as much work as possible in the face of errors.
79 .TP
80 .B -n
81 Print, but do not execute, the commands
82 needed to update the targets.
83 .TP
84 .B -s
85 Make the command line arguments sequentially rather than in parallel.
86 .TP
87 .B -t
88 Touch (update the modified date of) file targets, without
89 executing any recipes.
90 .TP
91 .BI -w target1 , target2,...
92 Pretend the modify time for each
93 .I target
94 is the current time; useful in conjunction with
95 .B -n
96 to learn what updates would be triggered by
97 modifying the
98 .IR targets .
99 .PD
100 .SS The \fLmkfile\fP
101 A
102 .I mkfile
103 consists of
104 .I assignments
105 (described under `Environment') and
106 .IR rules .
107 A rule contains
108 .I targets
109 and a
110 .IR tail .
111 A target is a literal string
112 and is normally a file name.
113 The tail contains zero or more
114 .I prerequisites
115 and an optional
116 .IR recipe ,
117 which is an
118 .B shell
119 script.
120 Each line of the recipe must begin with white space.
121 A rule takes the form
122 .IP
123 .EX
124 target: prereq1 prereq2
125 \f2recipe using\fP prereq1, prereq2 \f2to build\fP target
126 .EE
127 .PP
128 When the recipe is executed,
129 the first character on every line is elided.
130 .PP
131 After the colon on the target line, a rule may specify
132 .IR attributes ,
133 described below.
134 .PP
135 A
136 .I meta-rule
137 has a target of the form
138 .IB A % B
139 where
140 .I A
141 and
142 .I B
143 are (possibly empty) strings.
144 A meta-rule acts as a rule for any potential target whose
145 name matches
146 .IB A % B
147 with
148 .B %
149 replaced by an arbitrary string, called the
150 .IR stem .
151 In interpreting a meta-rule,
152 the stem is substituted for all occurrences of
153 .B %
154 in the prerequisite names.
155 In the recipe of a meta-rule, the environment variable
156 .B $stem
157 contains the string matched by the
158 .BR % .
159 For example, a meta-rule to compile a C program using
160 .IR 9c (1)
161 might be:
162 .IP
163 .EX
164 %: %.c
165 9c -c $stem.c
166 9l -o $stem $stem.o
167 .EE
168 .PP
169 Meta-rules may contain an ampersand
170 .B &
171 rather than a percent sign
172 .BR % .
173 A
174 .B %
175 matches a maximal length string of any characters;
176 an
177 .B &
178 matches a maximal length string of any characters except period
179 or slash.
180 .PP
181 The text of the
182 .I mkfile
183 is processed as follows.
184 Lines beginning with
185 .B <
186 followed by a file name are replaced by the contents of the named
187 file.
188 Lines beginning with
189 .B "<|"
190 followed by a file name are replaced by the output
191 of the execution of the named
192 file.
193 Blank lines and comments, which run from unquoted
194 .B #
195 characters to the following newline, are deleted.
196 The character sequence backslash-newline is deleted,
197 so long lines in
198 .I mkfile
199 may be folded.
200 Non-recipe lines are processed by substituting for
201 .BI `{ command }
202 the output of the
203 .I command
204 when run by
205 .IR sh .
206 References to variables are replaced by the variables' values.
207 Special characters may be quoted using single quotes
208 .BR \&''
209 as in
210 .IR sh (1).
211 .PP
212 Assignments and rules are distinguished by
213 the first unquoted occurrence of
214 .B :
215 (rule)
216 or
217 .B =
218 (assignment).
219 .PP
220 A later rule may modify or override an existing rule under the
221 following conditions:
222 .TP
223 \-
224 If the targets of the rules exactly match and one rule
225 contains only a prerequisite clause and no recipe, the
226 clause is added to the prerequisites of the other rule.
227 If either or both targets are virtual, the recipe is
228 always executed.
229 .TP
230 \-
231 If the targets of the rules match exactly and the
232 prerequisites do not match and both rules
233 contain recipes,
234 .I mk
235 reports an ``ambiguous recipe'' error.
236 .TP
237 \-
238 If the target and prerequisites of both rules match exactly,
239 the second rule overrides the first.
240 .SS Environment
241 Rules may make use of
242 shell
243 environment variables.
244 A legal reference of the form
245 .B $OBJ
246 or
247 .B ${name}
248 is expanded as in
249 .IR sh (1).
250 A reference of the form
251 .BI ${name: A % B = C\fL%\fID\fL}\fR,
252 where
253 .I A, B, C, D
254 are (possibly empty) strings,
255 has the value formed by expanding
256 .B $name
257 and substituting
258 .I C
259 for
260 .I A
261 and
262 .I D
263 for
264 .I B
265 in each word in
266 .B $name
267 that matches pattern
268 .IB A % B\f1.
269 .PP
270 Variables can be set by
271 assignments of the form
272 .I
273 var\fL=\fR[\fIattr\fL=\fR]\fIvalue\fR
274 .br
275 Blanks in the
276 .I value
277 break it into words.
278 Such variables are exported
279 to the environment of
280 recipes as they are executed, unless
281 .BR U ,
282 the only legal attribute
283 .IR attr ,
284 is present.
285 The initial value of a variable is
286 taken from (in increasing order of precedence)
287 the default values below,
288 .I mk's
289 environment, the
290 .IR mkfiles ,
291 and any command line assignment as an argument to
292 .IR mk .
293 A variable assignment argument overrides the first (but not any subseque…
294 assignment to that variable.
295 .PP
296 The variable
297 .B MKFLAGS
298 contains all the option arguments (arguments starting with
299 .L -
300 or containing
301 .LR = )
302 and
303 .B MKARGS
304 contains all the targets in the call to
305 .IR mk .
306 .PP
307 The variable
308 .B MKSHELL
309 contains the shell command line
310 .I mk
311 uses to run recipes.
312 If the first word of the command ends in
313 .B rc
314 or
315 .BR rcsh ,
316 .I mk
317 uses
318 .IR rc (1)'s
319 quoting rules; otherwise it uses
320 .IR sh (1)'s.
321 The
322 .B MKSHELL
323 variable is consulted when the mkfile is read, not when it is executed,
324 so that different shells can be used within a single mkfile:
325 .IP
326 .EX
327 MKSHELL=$PLAN9/bin/rc
328 use-rc:V:
329 for(i in a b c) echo $i
330
331 MKSHELL=sh
332 use-sh:V:
333 for i in a b c; do echo $i; done
334 .EE
335 .LP
336 Mkfiles included via
337 .B <
338 or
339 .B <|
340 .RI ( q.v. )
341 see their own private copy of
342 .BR MKSHELL ,
343 which always starts set to
344 .B sh .
345 .PP
346 Dynamic information may be included in the mkfile by using a line of the…
347 .IP
348 \fR<|\fIcommand\fR \fIargs\fR
349 .LP
350 This runs the command
351 .I command
352 with the given arguments
353 .I args
354 and pipes its standard output to
355 .I mk
356 to be included as part of the mkfile. For instance, the Inferno kernels
357 use this technique
358 to run a shell command with an awk script and a configuration
359 file as arguments in order for
360 the
361 .I awk
362 script to process the file and output a set of variables and their value…
363 .SS Execution
364 .PP
365 During execution,
366 .I mk
367 determines which targets must be updated, and in what order,
368 to build the
369 .I names
370 specified on the command line.
371 It then runs the associated recipes.
372 .PP
373 A target is considered up to date if it has no prerequisites or
374 if all its prerequisites are up to date and it is newer
375 than all its prerequisites.
376 Once the recipe for a target has executed, the target is
377 considered up to date.
378 .PP
379 The date stamp
380 used to determine if a target is up to date is computed
381 differently for different types of targets.
382 If a target is
383 .I virtual
384 (the target of a rule with the
385 .B V
386 attribute),
387 its date stamp is initially zero; when the target is
388 updated the date stamp is set to
389 the most recent date stamp of its prerequisites.
390 Otherwise, if a target does not exist as a file,
391 its date stamp is set to the most recent date stamp of its prerequisites,
392 or zero if it has no prerequisites.
393 Otherwise, the target is the name of a file and
394 the target's date stamp is always that file's modification date.
395 The date stamp is computed when the target is needed in
396 the execution of a rule; it is not a static value.
397 .PP
398 Nonexistent targets that have prerequisites
399 and are themselves prerequisites are treated specially.
400 Such a target
401 .I t
402 is given the date stamp of its most recent prerequisite
403 and if this causes all the targets which have
404 .I t
405 as a prerequisite to be up to date,
406 .I t
407 is considered up to date.
408 Otherwise,
409 .I t
410 is made in the normal fashion.
411 The
412 .B -i
413 flag overrides this special treatment.
414 .PP
415 Files may be made in any order that respects
416 the preceding restrictions.
417 .PP
418 A recipe is executed by supplying the recipe as standard input to
419 the command
420 .BR /bin/sh .
421 (Note that unlike
422 .IR make ,
423 .I mk
424 feeds the entire recipe to the shell rather than running each line
425 of the recipe separately.)
426 The environment is augmented by the following variables:
427 .TP 14
428 .B $alltarget
429 all the targets of this rule.
430 .TP
431 .B $newprereq
432 the prerequisites that caused this rule to execute.
433 .TP
434 .B $newmember
435 the prerequisites that are members of an aggregate
436 that caused this rule to execute.
437 When the prerequisites of a rule are members of an
438 aggregate,
439 .B $newprereq
440 contains the name of the aggregate and out of date
441 members, while
442 .B $newmember
443 contains only the name of the members.
444 .TP
445 .B $nproc
446 the process slot for this recipe.
447 It satisfies
448 .RB 0≤ $nproc < $NPROC .
449 .TP
450 .B $pid
451 the process id for the
452 .I mk
453 executing the recipe.
454 .TP
455 .B $prereq
456 all the prerequisites for this rule.
457 .TP
458 .B $stem
459 if this is a meta-rule,
460 .B $stem
461 is the string that matched
462 .B %
463 or
464 .BR & .
465 Otherwise, it is empty.
466 For regular expression meta-rules (see below), the variables
467 .LR stem0 ", ...,"
468 .L stem9
469 are set to the corresponding subexpressions.
470 .TP
471 .B $target
472 the targets for this rule that need to be remade.
473 .PP
474 These variables are available only during the execution of a recipe,
475 not while evaluating the
476 .IR mkfile .
477 .PP
478 Unless the rule has the
479 .B Q
480 attribute,
481 the recipe is printed prior to execution
482 with recognizable environment variables expanded.
483 Commands returning error status
484 cause
485 .I mk
486 to terminate.
487 .PP
488 Recipes and backquoted
489 .B rc
490 commands in places such as assignments
491 execute in a copy of
492 .I mk's
493 environment; changes they make to
494 environment variables are not visible from
495 .IR mk .
496 .PP
497 Variable substitution in a rule is done when
498 the rule is read; variable substitution in the recipe is done
499 when the recipe is executed. For example:
500 .IP
501 .EX
502 bar=a.c
503 foo: $bar
504 $CC -o foo $bar
505 bar=b.c
506 .EE
507 .PP
508 will compile
509 .B b.c
510 into
511 .BR foo ,
512 if
513 .B a.c
514 is newer than
515 .BR foo .
516 .SS Aggregates
517 Names of the form
518 .IR a ( b )
519 refer to member
520 .I b
521 of the aggregate
522 .IR a .
523 Currently, the only aggregates supported are
524 .I 9ar
525 (see
526 .IR 9c (1))
527 archives.
528 .SS Attributes
529 The colon separating the target from the prerequisites
530 may be
531 immediately followed by
532 .I attributes
533 and another colon.
534 The attributes are:
535 .TP
536 .B D
537 If the recipe exits with a non-null status, the target is deleted.
538 .TP
539 .B E
540 Continue execution if the recipe draws errors.
541 .TP
542 .B N
543 If there is no recipe, the target has its time updated.
544 .TP
545 .B n
546 The rule is a meta-rule that cannot be a target of a virtual rule.
547 Only files match the pattern in the target.
548 .TP
549 .B P
550 The characters after the
551 .B P
552 until the terminating
553 .B :
554 are taken as a program name.
555 It will be invoked as
556 .B "sh -c prog 'arg1' 'arg2'"
557 and should return a zero exit status
558 if and only if arg1 is up to date with respect to arg2.
559 Date stamps are still propagated in the normal way.
560 .TP
561 .B Q
562 The recipe is not printed prior to execution.
563 .TP
564 .B R
565 The rule is a meta-rule using regular expressions.
566 In the rule,
567 .B %
568 has no special meaning.
569 The target is interpreted as a regular expression as defined in
570 .IR regexp (7).
571 The prerequisites may contain references
572 to subexpressions in form
573 .BI \e n\f1,
574 as in the substitute command of
575 .IR sed (1).
576 .TP
577 .B U
578 The targets are considered to have been updated
579 even if the recipe did not do so.
580 .TP
581 .B V
582 The targets of this rule are marked as virtual.
583 They are distinct from files of the same name.
584 .PD
585 .SH EXAMPLES
586 A simple mkfile to compile a program:
587 .IP
588 .EX
589 .ta 8n +8n +8n +8n +8n +8n +8n
590 </$objtype/mkfile
591
592 prog: a.$O b.$O c.$O
593 $LD $LDFLAGS -o $target $prereq
594
595 %.$O: %.c
596 $CC $CFLAGS $stem.c
597 .EE
598 .PP
599 Override flag settings in the mkfile:
600 .IP
601 .EX
602 % mk target 'CFLAGS=-S -w'
603 .EE
604 .PP
605 Maintain a library:
606 .IP
607 .EX
608 libc.a(%.$O):N: %.$O
609 libc.a: libc.a(abs.$O) libc.a(access.$O) libc.a(alarm.$O) ...
610 ar r libc.a $newmember
611 .EE
612 .PP
613 String expression variables to derive names from a master list:
614 .IP
615 .EX
616 NAMES=alloc arc bquote builtins expand main match mk var word
617 OBJ=${NAMES:%=%.$O}
618 .EE
619 .PP
620 Regular expression meta-rules:
621 .IP
622 .EX
623 ([^/]*)/(.*)\e.$O:R: \e1/\e2.c
624 cd $stem1; $CC $CFLAGS $stem2.c
625 .EE
626 .PP
627 A correct way to deal with
628 .IR yacc (1)
629 grammars.
630 The file
631 .B lex.c
632 includes the file
633 .B x.tab.h
634 rather than
635 .B y.tab.h
636 in order to reflect changes in content, not just modification time.
637 .IP
638 .EX
639 lex.$O: x.tab.h
640 x.tab.h: y.tab.h
641 cmp -s x.tab.h y.tab.h || cp y.tab.h x.tab.h
642 y.tab.c y.tab.h: gram.y
643 $YACC -d gram.y
644 .EE
645 .PP
646 The above example could also use the
647 .B P
648 attribute for the
649 .B x.tab.h
650 rule:
651 .IP
652 .EX
653 x.tab.h:Pcmp -s: y.tab.h
654 cp y.tab.h x.tab.h
655 .EE
656 .SH SOURCE
657 .B \*9/src/cmd/mk
658 .SH SEE ALSO
659 .IR sh (1),
660 .IR regexp (7)
661 .PP
662 A. Hume,
663 ``Mk: a Successor to Make''
664 (Tenth Edition Research Unix Manuals).
665 .PP
666 Andrew G. Hume and Bob Flandrena,
667 ``Maintaining Files on Plan 9 with Mk''.
668 DOCPREFIX/doc/mk.pdf
669 .SH HISTORY
670 Andrew Hume wrote
671 .I mk
672 for Tenth Edition Research Unix.
673 It was later ported to Plan 9.
674 This software is a port of the Plan 9 version back to Unix.
675 .SH BUGS
676 Identical recipes for regular expression meta-rules only have one target.
677 .PP
678 Seemingly appropriate input like
679 .B CFLAGS=-DHZ=60
680 is parsed as an erroneous attribute; correct it by inserting
681 a space after the first
682 .LR = .
683 .PP
684 The recipes printed by
685 .I mk
686 before being passed to
687 the shell
688 for execution are sometimes erroneously expanded
689 for printing. Don't trust what's printed; rely
690 on what the shell
691 does.
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