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.TH MK 1

.SH NAME

mk, membername \- maintain (make) related files

.SH SYNOPSIS

.B mk

[

.B -f

.I mkfile

] ...

[

.I option ...

]

[

.I target ...

]

.PP

.B membername

.I aggregate ...

.SH DESCRIPTION

.I Mk

uses the dependency rules specified in

.I mkfile

to control the update (usually by compilation) of

.I targets

(usually files)

from the source files upon which they depend.

The

.I mkfile

(default

.LR mkfile )

contains a

.I rule

for each target that identifies the files and other

targets upon which it depends and an

.IR rc (1)

script, a

.IR 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.

.I Mkfile

may also contain

.I meta-rules

that define actions for updating implicit targets.

If no

.I target

is specified, the target of the first rule (not meta-rule) in

.I mkfile

is updated.

.PP

The environment variable

.B $NPROC

determines how many targets may be updated simultaneously;

Plan 9 sets

.B $NPROC

automatically to the number of CPUs on the current machine.

.PP

Options are:

.TP \w'\fL-d[egp]\ 'u

.B -a

Assume all targets to be out of date.

Thus, everything is updated.

.PD 0

.TP

.BR -d [ egp ]

Produce debugging output

.RB ( p

is for parsing,

.B g

for graph building,

.B e

for execution).

.TP

.B -e

Explain why each target is made.

.TP

.B -i

Force any missing intermediate targets to be made.

.TP

.B -k

Do as much work as possible in the face of errors.

.TP

.B -n

Print, but do not execute, the commands

needed to update the targets.

.TP

.B -s

Make the command line arguments sequentially rather than in parallel.

.TP

.B -t

Touch (update the modified date of) file targets, without

executing any recipes.

.TP

.BI -w target1 , target2,...

Pretend the modify time for each

.I target

is the current time; useful in conjunction with

.B -n

to learn what updates would be triggered by

modifying the

.IR targets .

.PD

.PP

The

.IR rc (1)

script

.I membername

extracts member names

(see `Aggregates' below)

from its arguments.

.SS The \fLmkfile\fP

A

.I mkfile

consists of

.I assignments

(described under `Environment') and

.IR rules .

A rule contains

.I targets

and a

.IR tail .

A target is a literal string

and is normally a file name.

The tail contains zero or more 

.I prerequisites

and an optional

.IR recipe ,

which is an

.B rc

script.

Each line of the recipe must begin with white space.

A rule takes the form

.IP

.EX

target: prereq1 prereq2

        rc \f2recipe using\fP prereq1, prereq2 \f2to build\fP target

.EE

.PP

When the recipe is executed,

the first character on every line is elided.

.PP

After the colon on the target line, a rule may specify

.IR attributes ,

described below.

.PP

A

.I meta-rule 

has a target of the form

.IB A % B

where

.I A

and

.I B

are (possibly empty) strings.

A meta-rule acts as a rule for any potential target whose

name matches

.IB A % B

with

.B %

replaced by an arbitrary string, called the

.IR stem .

In interpreting a meta-rule,

the stem is substituted for all occurrences of

.B %

in the prerequisite names.

In the recipe of a meta-rule, the environment variable

.B $stem

contains the string matched by the

.BR % .

For example, a meta-rule to compile a C program using

.IR 8c (1)

might be:

.IP

.EX

%:    %.c

        8c $stem.c

        8l -o $stem $stem.8

.EE

.PP

Meta-rules may contain an ampersand

.B &

rather than a percent sign

.BR % .

A

.B %

matches a maximal length string of any characters;

an

.B &

matches a maximal length string of any characters except period

or slash.

.PP

The text of the

.I mkfile

is processed as follows.

Lines beginning with

.B <

followed by a file name are replaced by the contents of the named

file.

Lines beginning with

.B "<|"

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

.B #

characters to the following newline, are deleted.

The character sequence backslash-newline is deleted,

so long lines in

.I mkfile

may be folded.

Non-recipe lines are processed by substituting for

.BI `{ command }

the output of the

.I command

when run by

.IR rc .

References to variables are replaced by the variables' values.

Special characters may be quoted using single quotes

.BR \&''

as in

.IR rc (1).

.PP

Assignments and rules are distinguished by

the first unquoted occurrence of

.B :

(rule)

or

.B =

(assignment).

.PP

A later rule may modify or override an existing rule under the

following conditions:

.TP

\-

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.

.TP

\-

If the targets of the rules match exactly and the

prerequisites do not match and both rules

contain recipes,

.I mk

reports an ``ambiguous recipe'' error.

.TP

\-

If the target and prerequisites of both rules match exactly,

the second rule overrides the first.

.SS Environment

Rules may make use of

.B rc

environment variables.

A legal reference of the form

.B $OBJ

is expanded as in

.IR rc (1).

A reference of the form

.BI ${name: A % B = C\fL%\fID\fL}\fR,

where

.I A, B, C, D

are (possibly empty) strings,

has the value formed by expanding

.B $name

and substituting

.I C

for

.I A

and

.I D

for

.I B

in each word in

.B $name

that matches pattern

.IB A % B\f1.

.PP

Variables can be set by

assignments of the form

.I

        var\fL=\fR[\fIattr\fL=\fR]\fIvalue\fR

.br

Blanks in the

.I value

break it into words, as in

.I rc

but without the surrounding parentheses.

Such variables are exported

to the environment of

recipes as they are executed, unless

.BR U ,

the only legal attribute

.IR attr ,

is present.

The initial value of a variable is

taken from (in increasing order of precedence)

the default values below,

.I mk's

environment, the

.IR mkfiles ,

and any command line assignment as an argument to

.IR mk .

A variable assignment argument overrides the first (but not any subsequent)

assignment to that variable.

.PP

The variable

.B MKFLAGS

contains all the option arguments (arguments starting with

.L -

or containing

.LR = )

and

.B MKARGS

contains all the targets in the call to

.IR mk .

.PP

It is recommended that mkfiles start with

.IP

.EX

</$objtype/mkfile

.EE

.PP

to set

.BR CC ,

.BR LD ,

.BR AS ,

.BR O ,

.BR YACC ,

and

.B MK

to values appropriate to the target architecture (see the examples below).

.SS Execution

.PP

During execution,

.I mk

determines which targets must be updated, and in what order,

to build the

.I names

specified on the command line.

It then runs the associated recipes.

.PP

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 prerequisites.

Once the recipe for a target has executed, the target is

considered up to date.

.PP

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

.I virtual

(the target of a rule with the

.B V

attribute),

its date stamp is initially 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.

Otherwise, 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 value.

.PP

Nonexistent targets that have prerequisites

and are themselves prerequisites are treated specially.

Such a target

.I t

is given the date stamp of its most recent prerequisite

and if this causes all the targets which have

.I t

as a prerequisite to be up to date,

.I t

is considered up to date.

Otherwise,

.I t

is made in the normal fashion.

The

.B -i

flag overrides this special treatment.

.PP

Files may be made in any order that respects

the preceding restrictions.

.PP

A recipe is executed by supplying the recipe as standard input to

the command

.B

        /bin/rc -e -I

.br

(the

.B -e

is omitted if the

.B E

attribute is set).

The environment is augmented by the following variables:

.TP 14

.B $alltarget

all the targets of this rule.

.TP

.B $newprereq

the prerequisites that caused this rule to execute.

.TP

.B $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,

.B $newprereq

contains the name of the aggregate and out of date

members, while

.B $newmember

contains only the name of the members.

.TP

.B $nproc

the process slot for this recipe.

It satisfies

.RB 0≤ $nproc < $NPROC .

.TP

.B $pid

the process id for the

.I mk

executing the recipe.

.TP

.B $prereq

all the prerequisites for this rule.

.TP

.B $stem

if this is a meta-rule,

.B $stem

is the string that matched

.B %

or

.BR & .

Otherwise, it is empty.

For regular expression meta-rules (see below), the variables

.LR stem0 ", ...,"

.L stem9

are set to the corresponding subexpressions.

.TP

.B $target

the targets for this rule that need to be remade.

.PP

These variables are available only during the execution of a recipe,

not while evaluating the

.IR mkfile .

.PP

Unless the rule has the

.B Q

attribute,

the recipe is printed prior to execution

with recognizable environment variables expanded.

Commands returning nonempty status (see

.IR intro (1))

cause

.I mk

to terminate.

.PP

Recipes and backquoted

.B rc

commands in places such as assignments

execute in a copy of

.I mk's

environment; changes they make to

environment variables are not visible from

.IR mk .

.PP

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 example:

.IP

.EX

bar=a.c

foo:	$bar

        $CC -o foo $bar

bar=b.c

.EE

.PP

will compile

.B b.c

into

.BR foo ,

if

.B a.c

is newer than

.BR foo .

.SS Aggregates

Names of the form

.IR a ( b )

refer to member

.I b

of the aggregate

.IR a .

Currently, the only aggregates supported are

.IR ar (1)

archives.

.SS Attributes

The colon separating the target from the prerequisites

may be

immediately followed by

.I attributes

and another colon.

The attributes are:

.TP

.B D

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

.TP

.B E

Continue execution if the recipe draws errors.

.TP

.B N

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

.TP

.B n

The rule is a meta-rule that cannot be a target of a virtual rule.

Only files match the pattern in the target.

.TP

.B P

The characters after the

.B P

until the terminating

.B :

are taken as a program name.

It will be invoked as

.B "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.

.TP

.B Q

The recipe is not printed prior to execution.

.TP

.B R

The rule is a meta-rule using regular expressions.

In the rule,

.B %

has no special meaning.

The target is interpreted as a regular expression as defined in

.IR regexp (6).

The prerequisites may contain references

to subexpressions in form

.BI \e n\f1,

as in the substitute command of

.IR sam (1).

.TP

.B U

The targets are considered to have been updated

even if the recipe did not do so.

.TP

.B V

The targets of this rule are marked as virtual.

They are distinct from files of the same name.

.PD

.SH EXAMPLES

A simple mkfile to compile a program:

.IP

.EX

.ta 8n +8n +8n +8n +8n +8n +8n

</$objtype/mkfile

prog:	a.$O b.$O c.$O

	$LD $LDFLAGS -o $target $prereq

%.$O:	%.c

	$CC $CFLAGS $stem.c

.EE

.PP

Override flag settings in the mkfile:

.IP

.EX

% mk target 'CFLAGS=-S -w'

.EE

.PP

Maintain a library:

.IP

.EX

libc.a(%.$O):N:	%.$O

libc.a:	libc.a(abs.$O) libc.a(access.$O) libc.a(alarm.$O) ...

	ar r libc.a $newmember

.EE

.PP

String expression variables to derive names from a master list:

.IP

.EX

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

OBJ=${NAMES:%=%.$O}

.EE

.PP

Regular expression meta-rules:

.IP

.EX

([^/]*)/(.*)\e.$O:R:  \e1/\e2.c

	cd $stem1; $CC $CFLAGS $stem2.c

.EE

.PP

A correct way to deal with

.IR yacc (1)

grammars.

The file

.B lex.c

includes the file

.B x.tab.h

rather than

.B y.tab.h

in order to reflect changes in content, not just modification time.

.IP

.EX

lex.$O:	x.tab.h

x.tab.h:	y.tab.h

	cmp -s x.tab.h y.tab.h || cp y.tab.h x.tab.h

y.tab.c y.tab.h:	gram.y

	$YACC -d gram.y

.EE

.PP

The above example could also use the

.B P

attribute for the

.B x.tab.h

rule:

.IP

.EX

x.tab.h:Pcmp -s:	y.tab.h

	cp y.tab.h x.tab.h

.EE

.SH SOURCE

.B /sys/src/cmd/mk

.SH SEE ALSO

.IR rc (1),

.IR regexp (6)

.PP

A. Hume,

``Mk: a Successor to Make''.

.PP

Andrew G. Hume and Bob Flandrena,

``Maintaining Files on Plan 9 with Mk''.

.SH BUGS

Identical recipes for regular expression meta-rules only have one target.

.PP

Seemingly appropriate input like

.B CFLAGS=-DHZ=60

is parsed as an erroneous attribute; correct it by inserting

a space after the first 

.LR = .

.PP

The recipes printed by

.I mk

before being passed to

.I rc

for execution are sometimes erroneously expanded

for printing.  Don't trust what's printed; rely

on what

.I rc

does.