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MK(1)									 MK(1)

       mk, membername - maintain (make) related files

       mk [ -f mkfile ] ...  [ option ...  ] [ target ...  ]

       membername aggregate ...

       Mk  uses the dependency rules specified in mkfile to control the update
       (usually by compilation) of targets (usually  files)  from  the	source
       files  upon which they depend.  The mkfile (default contains a rule for
       each target that identifies the files and other targets upon  which  it
       depends	and  an	 rc(1)	script,	 a  recipe, to update the target.  The
       script is run if the target does not exist or if it is older  than  any
       of  the	files  it depends on.  Mkfile may also contain meta-rules that
       define actions for updating implicit targets.  If no target  is	speci‐
       fied,  the  target  of  the  first  rule	 (not  meta-rule) in mkfile is

       The environment variable $NPROC determines  how	many  targets  may  be
       updated	simultaneously; Plan 9 sets $NPROC automatically to the number
       of CPUs on the current machine.

       Options are:

       -a      Assume all targets to be out  of	 date.	 Thus,	everything  is
       -d[egp] Produce	debugging output (p is for parsing, g for graph build‐
	       ing, e for execution).
       -e      Explain why each target is made.
       -i      Force any missing intermediate targets to be made.
       -k      Do as much work as possible in the face of errors.
       -n      Print, but do not execute, the commands needed  to  update  the
       -s      Make  the  command  line	 arguments sequentially rather than in
       -t      Touch (update the modified date of) file targets, without  exe‐
	       cuting any recipes.
	       Pretend	the  modify  time for each target is the current time;
	       useful in conjunction with -n to learn what  updates  would  be
	       triggered by modifying the targets.

       The  rc(1)  script  membername  extracts member names (see `Aggregates'
       below) from its arguments.

   The mkfile
       A mkfile consists of assignments (described  under  `Environment')  and
       rules.	A  rule	 contains  targets  and a tail.	 A target is a literal
       string and is normally a file name.  The tail  contains	zero  or  more
       prerequisites and an optional recipe, which is an rc script.  Each line
       of the recipe must begin with white space.  A rule takes the form

	      target: prereq1 prereq2
		      rc recipe using prereq1, prereq2 to build target

       When the recipe is executed, the	 first	character  on  every  line  is

       After  the  colon  on  the  target line, a rule may specify attributes,
       described below.

       A meta-rule has a target of the form A%B where A and  B	are  (possibly
       empty)  strings.	  A  meta-rule acts as a rule for any potential target
       whose name matches A%B with % replaced by an arbitrary  string,	called
       the stem.  In interpreting a meta-rule, the stem is substituted for all
       occurrences of % in the prerequisite names.  In the recipe of  a	 meta-
       rule, the environment variable $stem contains the string matched by the
       %.  For example, a meta-rule to compile a C program using  8c(1)	 might

	      %:    %.c
		      8c $stem.c
		      8l -o $stem $stem.8

       Meta-rules  may contain an ampersand & rather than a percent sign %.  A
       % matches a maximal length string of any characters;  an	 &  matches  a
       maximal length string of any characters except period or slash.

       The text of the mkfile is processed as follows.	Lines beginning with <
       followed by a file name are replaced by the contents of the named file.
       Lines  beginning	 with  <|  followed by a file name are replaced by the
       output of the execution of the named file.  Blank lines	and  comments,
       which  run  from	 unquoted  #  characters to the following newline, are
       deleted.	 The character sequence backslash-newline is deleted, so  long
       lines  in mkfile may be folded.	Non-recipe lines are processed by sub‐
       stituting for `{command} the output of the  command  when  run  by  rc.
       References to variables are replaced by the variables' values.  Special
       characters may be quoted using single quotes '' as in rc(1).

       Assignments and rules are distinguished by the  first  unquoted	occur‐
       rence of : (rule) or = (assignment).

       A  later rule may modify or override an existing rule under the follow‐
       ing conditions:

       -      If the targets of the rules exactly match and one rule  contains
	      only a prerequisite clause and no recipe, the clause is added to
	      the prerequisites of the other rule.  If either or both  targets
	      are virtual, the recipe is always executed.

       -      If  the targets of the rules match exactly and the prerequisites
	      do not match and both  rules  contain  recipes,  mk  reports  an
	      ``ambiguous recipe'' error.

       -      If the target and prerequisites of both rules match exactly, the
	      second rule overrides the first.

       Rules may make use of rc environment variables.	A legal	 reference  of
       the  form  $OBJ	is  expanded  as  in  rc(1).   A reference of the form
       ${name:A%B=C%D}, where A, B, C, D are (possibly empty) strings, has the
       value formed by expanding $name and substituting C for A and D for B in
       each word in $name that matches pattern A%B.

       Variables can be set by assignments of the form
       Blanks in the value break it into words, as in rc but without the  sur‐
       rounding	 parentheses.	Such variables are exported to the environment
       of recipes as they are executed, unless U,  the	only  legal  attribute
       attr,  is  present.   The initial value of a variable is taken from (in
       increasing order of precedence) the default values below, mk's environ‐
       ment,  the  mkfiles,  and any command line assignment as an argument to
       mk.  A variable assignment argument overrides the first	(but  not  any
       subsequent) assignment to that variable.

       The  variable  MKFLAGS  contains	 all  the  option arguments (arguments
       starting with or containing and MKARGS contains all the targets in  the
       call to mk.

       It is recommended that mkfiles start with


       to  set CC, LD, AS, O, YACC, and MK to values appropriate to the target
       architecture (see the examples below).

       During execution, mk determines which targets must be updated,  and  in
       what  order, to build the names specified on the command line.  It then
       runs the associated recipes.

       A target is considered up to date if it has no prerequisites or if  all
       its prerequisites are up to date and it is newer than all its prerequi‐
       sites.  Once the recipe for a target has executed, the target  is  con‐
       sidered up to date.

       The  date stamp used to determine if a target is up to date is computed
       differently for different types of targets.  If	a  target  is  virtual
       (the  target  of	 a  rule with the V attribute), its date stamp is ini‐
       tially zero; when the target is updated the date stamp is  set  to  the
       most  recent  date  stamp of its prerequisites.	Otherwise, if a target
       does not exist as a file, its date stamp is set to the most recent date
       stamp of its prerequisites, or zero if it has no prerequisites.	Other‐
       wise, the target is the name of a file and the target's date  stamp  is
       always  that file's modification date.  The date stamp is computed when
       the target is needed in the execution of a rule; it  is	not  a	static

       Nonexistent  targets that have prerequisites and are themselves prereq‐
       uisites are treated specially.  Such a target t is given the date stamp
       of  its	most  recent  prerequisite  and if this causes all the targets
       which have t as a prerequisite to be up to date, t is considered up  to
       date.   Otherwise,  t is made in the normal fashion.  The -i flag over‐
       rides this special treatment.

       Files may be made in any order that  respects  the  preceding  restric‐

       A  recipe  is executed by supplying the recipe as standard input to the
	       /bin/rc -e -I
       (the -e is omitted if the E attribute is set).  The environment is aug‐
       mented by the following variables:

       $alltarget    all the targets of this rule.

       $newprereq    the prerequisites that caused this rule to execute.

       $newmember    the  prerequisites	 that are members of an aggregate that
		     caused this rule to execute.  When the prerequisites of a
		     rule are members of an aggregate, $newprereq contains the
		     name of the aggregate and	out  of	 date  members,	 while
		     $newmember contains only the name of the members.

       $nproc	     the   process   slot   for	 this  recipe.	 It  satisfies

       $pid	     the process id for the mk executing the recipe.

       $prereq	     all the prerequisites for this rule.

       $stem	     if this is a meta-rule, $stem is the string that  matched
		     %	or &.  Otherwise, it is empty.	For regular expression
		     meta-rules (see below), the variables are set to the cor‐
		     responding subexpressions.

       $target	     the targets for this rule that need to be remade.

       These  variables	 are  available only during the execution of a recipe,
       not while evaluating the mkfile.

       Unless the rule has the Q attribute, the recipe	is  printed  prior  to
       execution  with	recognizable environment variables expanded.  Commands
       returning nonempty status (see intro(1)) cause mk to terminate.

       Recipes and backquoted rc commands in places such as  assignments  exe‐
       cute  in	 a  copy of mk's environment; changes they make to environment
       variables are not visible from mk.

       Variable substitution in a rule is done when the rule is read; variable
       substitution  in	 the  recipe is done when the recipe is executed.  For

	      foo: $bar
		      $CC -o foo $bar

       will compile b.c into foo, if a.c is newer than foo.

       Names of the form a(b) refer to member b	 of  the  aggregate  a.	  Cur‐
       rently, the only aggregates supported are ar(1) archives.

       The  colon  separating the target from the prerequisites may be immedi‐
       ately followed by attributes and another colon.	The attributes are:

       D      If the recipe exits  with	 a  non-null  status,  the  target  is

       E      Continue execution if the recipe draws errors.

       N      If there is no recipe, the target has its time updated.

       n      The  rule	 is  a	meta-rule that cannot be a target of a virtual
	      rule.  Only files match the pattern in the target.

       P      The characters after the P until the terminating : are taken  as
	      a	 program name.	It will be invoked as rc -c prog 'arg1' 'arg2'
	      and should return a null exit status if and only if arg1	is  up
	      to  date with respect to arg2.  Date stamps are still propagated
	      in the normal way.

       Q      The recipe is not printed prior to execution.

       R      The rule is a meta-rule using regular expressions.  In the rule,
	      %	 has no special meaning.  The target is interpreted as a regu‐
	      lar expression as defined in regexp(6).  The  prerequisites  may
	      contain  references to subexpressions in form \n, as in the sub‐
	      stitute command of sam(1).

       U      The targets are considered to have  been	updated	 even  if  the
	      recipe did not do so.

       V      The  targets  of this rule are marked as virtual.	 They are dis‐
	      tinct from files of the same name.

       A simple mkfile to compile a program:


	      prog:   a.$O b.$O c.$O
		      $LD $LDFLAGS -o $target $prereq

	      %.$O:   %.c
		      $CC $CFLAGS $stem.c

       Override flag settings in the mkfile:

	      % mk target 'CFLAGS=-S -w'

       Maintain a library:

	      libc.a(%.$O):N: %.$O
	      libc.a: libc.a(abs.$O) libc.a(access.$O) libc.a(alarm.$O) ...
		      ar r libc.a $newmember

       String expression variables to derive names from a master list:

	      NAMES=alloc arc bquote builtins expand main match mk var word

       Regular expression meta-rules:

	      ([^/]*)/(.*)\.$O:R:  \1/\2.c
		      cd $stem1; $CC $CFLAGS $stem2.c

       A correct way to deal with yacc(1) grammars.  The file  lex.c  includes
       the  file  rather  than in order to reflect changes in
       content, not just modification time.

		      cmp -s || cp	      gram.y
		      $YACC -d gram.y

       The above example could also use the P attribute for the rule: -s:


       rc(1), regexp(6)

       A. Hume, ``Mk: a Successor to Make''.

       Andrew G. Hume and Bob Flandrena, ``Maintaining Files on	 Plan  9  with

       Identical  recipes for regular expression meta-rules only have one tar‐

       Seemingly appropriate input like CFLAGS=-DHZ=60 is parsed as  an	 erro‐
       neous attribute; correct it by inserting a space after the first

       The  recipes  printed by mk before being passed to rc for execution are
       sometimes  erroneously  expanded	 for  printing.	  Don't	 trust	what's
       printed; rely on what rc does.

                             _         _         _ 
                            | |       | |       | |     
                            | |       | |       | |     
                         __ | | __ __ | | __ __ | | __  
                         \ \| |/ / \ \| |/ / \ \| |/ /  
                          \ \ / /   \ \ / /   \ \ / /   
                           \   /     \   /     \   /    
                            \_/       \_/       \_/ 
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