3
mk \- maintain (make) related files
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uses the dependency rules specified in
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to control the update (usually by compilation) of
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from the source files upon which they depend.
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for each target that identifies the files and other
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targets upon which it depends and an
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The script is run if the target does not exist
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or if it is older than any of the files it depends on.
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that define actions for updating implicit targets.
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is specified, the target of the first rule (not meta-rule) in
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The environment variable
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determines how many targets may be updated simultaneously;
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Some operating systems, e.g., Plan 9, set
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automatically to the number of CPUs on the current machine.
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Assume all targets to be out of date.
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Thus, everything is updated.
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Produce debugging output
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Explain why each target is made.
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Force any missing intermediate targets to be made.
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Do as much work as possible in the face of errors.
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Print, but do not execute, the commands
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needed to update the targets.
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Make the command line arguments sequentially rather than in parallel.
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Touch (update the modified date of) file targets, without
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executing any recipes.
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.BI -w target1 , target2,...
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Pretend the modify time for each
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is the current time; useful in conjunction with
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to learn what updates would be triggered by
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(described under `Environment') and
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A target is a literal string
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and is normally a file name.
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The tail contains zero or more
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Each line of the recipe must begin with white space.
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A rule takes the form
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target: prereq1 prereq2
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\f2recipe using\fP prereq1, prereq2 \f2to build\fP target
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When the recipe is executed,
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the first character on every line is elided.
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After the colon on the target line, a rule may specify
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has a target of the form
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are (possibly empty) strings.
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A meta-rule acts as a rule for any potential target whose
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replaced by an arbitrary string, called the
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In interpreting a meta-rule,
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the stem is substituted for all occurrences of
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in the prerequisite names.
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In the recipe of a meta-rule, the environment variable
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contains the string matched by the
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For example, a meta-rule to compile a C program using
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Meta-rules may contain an ampersand
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rather than a percent sign
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matches a maximal length string of any characters;
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matches a maximal length string of any characters except period
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is processed as follows.
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followed by a file name are replaced by the contents of the named
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followed by a file name are replaced by the output
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of the execution of the named
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Blank lines and comments, which run from unquoted
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characters to the following newline, are deleted.
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The character sequence backslash-newline is deleted,
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Non-recipe lines are processed by substituting for
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References to variables are replaced by the variables' values.
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Special characters may be quoted using single quotes
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Assignments and rules are distinguished by
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the first unquoted occurrence of
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A later rule may modify or override an existing rule under the
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following conditions:
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If the targets of the rules exactly match and one rule
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contains only a prerequisite clause and no recipe, the
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clause is added to the prerequisites of the other rule.
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If either or both targets are virtual, the recipe is
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If the targets of the rules match exactly and the
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prerequisites do not match and both rules
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reports an ``ambiguous recipe'' error.
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If the target and prerequisites of both rules match exactly,
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the second rule overrides the first.
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Rules may make use of
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environment variables.
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A legal reference of the form
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A reference of the form
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.BI ${name: A % B = C\fL%\fID\fL}\fR,
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are (possibly empty) strings,
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has the value formed by expanding
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Variables can be set by
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assignments of the form
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var\fL=\fR[\fIattr\fL=\fR]\fIvalue\fR
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Such variables are exported
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to the environment of
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recipes as they are executed, unless
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the only legal attribute
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The initial value of a variable is
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taken from (in increasing order of precedence)
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the default values below,
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and any command line assignment as an argument to
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A variable assignment argument overrides the first (but not any subsequent)
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assignment to that variable.
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contains all the option arguments (arguments starting with
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contains all the targets in the call to
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contains the shell command line
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If the first word of the command ends in
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quoting rules; otherwise it uses
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variable is consulted when the mkfile is read, not when it is executed,
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so that different shells can be used within a single mkfile:
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MKSHELL=$PLAN9/bin/rc
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for(i in a b c) echo $i
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for i in a b c; do echo $i; done
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see their own private copy of
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which always starts set to
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Dynamic information may be included in the mkfile by using a line of the form
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\fR<|\fIcommand\fR \fIargs\fR
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This runs the command
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with the given arguments
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and pipes its standard output to
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to be included as part of the mkfile. For instance, the Inferno kernels
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to run a shell command with an awk script and a configuration
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file as arguments in order for
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script to process the file and output a set of variables and their values.
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determines which targets must be updated, and in what order,
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specified on the command line.
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It then runs the associated recipes.
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A target is considered up to date if it has no prerequisites or
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if all its prerequisites are up to date and it is newer
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than all its prerequisites.
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Once the recipe for a target has executed, the target is
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considered up to date.
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used to determine if a target is up to date is computed
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differently for different types of targets.
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(the target of a rule with the
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its date stamp is initially zero; when the target is
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updated the date stamp is set to
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the most recent date stamp of its prerequisites.
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Otherwise, if a target does not exist as a file,
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its date stamp is set to the most recent date stamp of its prerequisites,
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or zero if it has no prerequisites.
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Otherwise, the target is the name of a file and
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the target's date stamp is always that file's modification date.
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The date stamp is computed when the target is needed in
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the execution of a rule; it is not a static value.
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Nonexistent targets that have prerequisites
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and are themselves prerequisites are treated specially.
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is given the date stamp of its most recent prerequisite
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and if this causes all the targets which have
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as a prerequisite to be up to date,
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is considered up to date.
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is made in the normal fashion.
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flag overrides this special treatment.
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Files may be made in any order that respects
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the preceding restrictions.
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A recipe is executed by supplying the recipe as standard input to
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feeds the entire recipe to the shell rather than running each line
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of the recipe separately.)
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The environment is augmented by the following variables:
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all the targets of this rule.
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the prerequisites that caused this rule to execute.
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the prerequisites that are members of an aggregate
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that caused this rule to execute.
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When the prerequisites of a rule are members of an
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contains the name of the aggregate and out of date
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contains only the name of the members.
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the process slot for this recipe.
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.RB 0≤ $nproc < $NPROC .
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the process id for the
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executing the recipe.
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all the prerequisites for this rule.
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if this is a meta-rule,
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is the string that matched
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Otherwise, it is empty.
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For regular expression meta-rules (see below), the variables
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are set to the corresponding subexpressions.
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the targets for this rule that need to be remade.
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These variables are available only during the execution of a recipe,
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not while evaluating the
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Unless the rule has the
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the recipe is printed prior to execution
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with recognizable environment variables expanded.
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Commands returning error status
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Recipes and backquoted
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commands in places such as assignments
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environment; changes they make to
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environment variables are not visible from
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Variable substitution in a rule is done when
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the rule is read; variable substitution in the recipe is done
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when the recipe is executed. For example:
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Currently, the only aggregates supported are
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The colon separating the target from the prerequisites
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immediately followed by
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If the recipe exits with a non-null status, the target is deleted.
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Continue execution if the recipe draws errors.
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If there is no recipe, the target has its time updated.
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The rule is a meta-rule that cannot be a target of a virtual rule.
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Only files match the pattern in the target.
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The characters after the
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until the terminating
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are taken as a program name.
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It will be invoked as
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.B "sh -c prog 'arg1' 'arg2'"
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and should return a zero exit status
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if and only if arg1 is up to date with respect to arg2.
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Date stamps are still propagated in the normal way.
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The recipe is not printed prior to execution.
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The rule is a meta-rule using regular expressions.
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has no special meaning.
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The target is interpreted as a regular expression as defined in
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The prerequisites may contain references
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to subexpressions in form
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as in the substitute command of
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The targets are considered to have been updated
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even if the recipe did not do so.
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The targets of this rule are marked as virtual.
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They are distinct from files of the same name.
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A simple mkfile to compile a program:
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.ta 8n +8n +8n +8n +8n +8n +8n
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$LD $LDFLAGS -o $target $prereq
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Override flag settings in the mkfile:
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% mk target 'CFLAGS=-S -w'
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libc.a: libc.a(abs.$O) libc.a(access.$O) libc.a(alarm.$O) ...
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ar r libc.a $newmember
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String expression variables to derive names from a master list:
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NAMES=alloc arc bquote builtins expand main match mk var word
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Regular expression meta-rules:
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([^/]*)/(.*)\e.$O:R: \e1/\e2.c
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cd $stem1; $CC $CFLAGS $stem2.c
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A correct way to deal with
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in order to reflect changes in content, not just modification time.
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cmp -s x.tab.h y.tab.h || cp y.tab.h x.tab.h
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y.tab.c y.tab.h: gram.y
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The above example could also use the
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x.tab.h:Pcmp -s: y.tab.h
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``Mk: a Successor to Make''
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(Tenth Edition Research Unix Manuals).
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Andrew G. Hume and Bob Flandrena,
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``Maintaining Files on Plan 9 with Mk''.
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for Tenth Edition Research Unix.
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It was later ported to Plan 9.
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This software is a port of the Plan 9 version back to Unix.
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Identical recipes for regular expression meta-rules only have one target.
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Seemingly appropriate input like
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is parsed as an erroneous attribute; correct it by inserting
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a space after the first
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The recipes printed by
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before being passed to
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for execution are sometimes erroneously expanded
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for printing. Don't trust what's printed; rely
added
removed
mk/mk.1.orig
