Backport security fix for absolute path traversal vulnerability in bsdcpio.

[FreeBSD/stable/10.git] / contrib / bmake / make.1

.\"     $NetBSD: make.1,v 1.249 2015/06/05 07:33:40 wiz Exp $
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.\"    notice, this list of conditions and the following disclaimer.
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.\"    notice, this list of conditions and the following disclaimer in the
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.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
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.\"     from: @(#)make.1        8.4 (Berkeley) 3/19/94
.\"
.Dd June 4, 2015
.Dt MAKE 1
.Os
.Sh NAME
.Nm make
.Nd maintain program dependencies
.Sh SYNOPSIS
.Nm
.Op Fl BeikNnqrstWwX
.Op Fl C Ar directory
.Op Fl D Ar variable
.Op Fl d Ar flags
.Op Fl f Ar makefile
.Op Fl I Ar directory
.Op Fl J Ar private
.Op Fl j Ar max_jobs
.Op Fl m Ar directory
.Op Fl T Ar file
.Op Fl V Ar variable
.Op Ar variable=value
.Op Ar target ...
.Sh DESCRIPTION
.Nm
is a program designed to simplify the maintenance of other programs.
Its input is a list of specifications as to the files upon which programs
and other files depend.
If no
.Fl f Ar makefile
makefile option is given,
.Nm
will try to open
.Ql Pa makefile
then
.Ql Pa Makefile
in order to find the specifications.
If the file
.Ql Pa .depend
exists, it is read (see
.Xr mkdep 1 ) .
.Pp
This manual page is intended as a reference document only.
For a more thorough description of
.Nm
and makefiles, please refer to
.%T "PMake \- A Tutorial" .
.Pp
.Nm
will prepend the contents of the
.Va MAKEFLAGS
environment variable to the command line arguments before parsing them.
.Pp
The options are as follows:
.Bl -tag -width Ds
.It Fl B
Try to be backwards compatible by executing a single shell per command and
by executing the commands to make the sources of a dependency line in sequence.
.It Fl C Ar directory
Change to
.Ar directory
before reading the makefiles or doing anything else.
If multiple
.Fl C
options are specified, each is interpreted relative to the previous one:
.Fl C Pa / Fl C Pa etc
is equivalent to
.Fl C Pa /etc .
.It Fl D Ar variable
Define
.Ar variable
to be 1, in the global context.
.It Fl d Ar [-]flags
Turn on debugging, and specify which portions of
.Nm
are to print debugging information.
Unless the flags are preceded by
.Ql \-
they are added to the
.Va MAKEFLAGS
environment variable and will be processed by any child make processes.
By default, debugging information is printed to standard error,
but this can be changed using the
.Ar F
debugging flag.
The debugging output is always unbuffered; in addition, if debugging
is enabled but debugging output is not directed to standard output,
then the standard output is line buffered.
.Ar Flags
is one or more of the following:
.Bl -tag -width Ds
.It Ar A
Print all possible debugging information;
equivalent to specifying all of the debugging flags.
.It Ar a
Print debugging information about archive searching and caching.
.It Ar C
Print debugging information about current working directory.
.It Ar c
Print debugging information about conditional evaluation.
.It Ar d
Print debugging information about directory searching and caching.
.It Ar e
Print debugging information about failed commands and targets.
.It Ar F Ns Oo Sy \&+ Oc Ns Ar filename
Specify where debugging output is written.
This must be the last flag, because it consumes the remainder of
the argument.
If the character immediately after the
.Ql F
flag is
.Ql \&+ ,
then the file will be opened in append mode;
otherwise the file will be overwritten.
If the file name is
.Ql stdout
or
.Ql stderr
then debugging output will be written to the
standard output or standard error output file descriptors respectively
(and the
.Ql \&+
option has no effect).
Otherwise, the output will be written to the named file.
If the file name ends
.Ql .%d
then the
.Ql %d
is replaced by the pid.
.It Ar f
Print debugging information about loop evaluation.
.It Ar "g1"
Print the input graph before making anything.
.It Ar "g2"
Print the input graph after making everything, or before exiting
on error.
.It Ar "g3"
Print the input graph before exiting on error.
.It Ar j
Print debugging information about running multiple shells.
.It Ar l
Print commands in Makefiles regardless of whether or not they are prefixed by
.Ql @
or other "quiet" flags.
Also known as "loud" behavior.
.It Ar M
Print debugging information about "meta" mode decisions about targets.
.It Ar m
Print debugging information about making targets, including modification
dates.
.It Ar n
Don't delete the temporary command scripts created when running commands.
These temporary scripts are created in the directory
referred to by the
.Ev TMPDIR
environment variable, or in
.Pa /tmp
if
.Ev TMPDIR
is unset or set to the empty string.
The temporary scripts are created by
.Xr mkstemp 3 ,
and have names of the form
.Pa makeXXXXXX .
.Em NOTE :
This can create many files in
.Ev TMPDIR
or
.Pa /tmp ,
so use with care.
.It Ar p
Print debugging information about makefile parsing.
.It Ar s
Print debugging information about suffix-transformation rules.
.It Ar t
Print debugging information about target list maintenance.
.It Ar V
Force the
.Fl V
option to print raw values of variables.
.It Ar v
Print debugging information about variable assignment.
.It Ar x
Run shell commands with
.Fl x
so the actual commands are printed as they are executed.
.El
.It Fl e
Specify that environment variables override macro assignments within
makefiles.
.It Fl f Ar makefile
Specify a makefile to read instead of the default
.Ql Pa makefile .
If
.Ar makefile
is
.Ql Fl ,
standard input is read.
Multiple makefiles may be specified, and are read in the order specified.
.It Fl I Ar directory
Specify a directory in which to search for makefiles and included makefiles.
The system makefile directory (or directories, see the
.Fl m
option) is automatically included as part of this list.
.It Fl i
Ignore non-zero exit of shell commands in the makefile.
Equivalent to specifying
.Ql Fl
before each command line in the makefile.
.It Fl J Ar private
This option should
.Em not
be specified by the user.
.Pp
When the
.Ar j
option is in use in a recursive build, this option is passed by a make
to child makes to allow all the make processes in the build to
cooperate to avoid overloading the system.
.It Fl j Ar max_jobs
Specify the maximum number of jobs that
.Nm
may have running at any one time.
The value is saved in
.Va .MAKE.JOBS .
Turns compatibility mode off, unless the
.Ar B
flag is also specified.
When compatibility mode is off, all commands associated with a
target are executed in a single shell invocation as opposed to the
traditional one shell invocation per line.
This can break traditional scripts which change directories on each
command invocation and then expect to start with a fresh environment
on the next line.
It is more efficient to correct the scripts rather than turn backwards
compatibility on.
.It Fl k
Continue processing after errors are encountered, but only on those targets
that do not depend on the target whose creation caused the error.
.It Fl m Ar directory
Specify a directory in which to search for sys.mk and makefiles included
via the
.Ao Ar file Ac Ns -style
include statement.
The
.Fl m
option can be used multiple times to form a search path.
This path will override the default system include path: /usr/share/mk.
Furthermore the system include path will be appended to the search path used
for
.Qo Ar file Qc Ns -style
include statements (see the
.Fl I
option).
.Pp
If a file or directory name in the
.Fl m
argument (or the
.Ev MAKESYSPATH
environment variable) starts with the string
.Qq \&.../
then
.Nm
will search for the specified file or directory named in the remaining part
of the argument string.
The search starts with the current directory of
the Makefile and then works upward towards the root of the filesystem.
If the search is successful, then the resulting directory replaces the
.Qq \&.../
specification in the
.Fl m
argument.
If used, this feature allows
.Nm
to easily search in the current source tree for customized sys.mk files
(e.g., by using
.Qq \&.../mk/sys.mk
as an argument).
.It Fl n
Display the commands that would have been executed, but do not
actually execute them unless the target depends on the .MAKE special
source (see below).
.It Fl N
Display the commands which would have been executed, but do not
actually execute any of them; useful for debugging top-level makefiles
without descending into subdirectories.
.It Fl q
Do not execute any commands, but exit 0 if the specified targets are
up-to-date and 1, otherwise.
.It Fl r
Do not use the built-in rules specified in the system makefile.
.It Fl s
Do not echo any commands as they are executed.
Equivalent to specifying
.Ql Ic @
before each command line in the makefile.
.It Fl T Ar tracefile
When used with the
.Fl j
flag,
append a trace record to
.Ar tracefile
for each job started and completed.
.It Fl t
Rather than re-building a target as specified in the makefile, create it
or update its modification time to make it appear up-to-date.
.It Fl V Ar variable
Print
.Nm Ns 's
idea of the value of
.Ar variable ,
in the global context.
Do not build any targets.
Multiple instances of this option may be specified;
the variables will be printed one per line,
with a blank line for each null or undefined variable.
If
.Ar variable
contains a
.Ql \&$
then the value will be expanded before printing.
.It Fl W
Treat any warnings during makefile parsing as errors.
.It Fl w
Print entering and leaving directory messages, pre and post processing.
.It Fl X
Don't export variables passed on the command line to the environment
individually.
Variables passed on the command line are still exported
via the
.Va MAKEFLAGS
environment variable.
This option may be useful on systems which have a small limit on the
size of command arguments.
.It Ar variable=value
Set the value of the variable
.Ar variable
to
.Ar value .
Normally, all values passed on the command line are also exported to
sub-makes in the environment.
The
.Fl X
flag disables this behavior.
Variable assignments should follow options for POSIX compatibility
but no ordering is enforced.
.El
.Pp
There are seven different types of lines in a makefile: file dependency
specifications, shell commands, variable assignments, include statements,
conditional directives, for loops, and comments.
.Pp
In general, lines may be continued from one line to the next by ending
them with a backslash
.Pq Ql \e .
The trailing newline character and initial whitespace on the following
line are compressed into a single space.
.Sh FILE DEPENDENCY SPECIFICATIONS
Dependency lines consist of one or more targets, an operator, and zero
or more sources.
This creates a relationship where the targets
.Dq depend
on the sources
and are usually created from them.
The exact relationship between the target and the source is determined
by the operator that separates them.
The three operators are as follows:
.Bl -tag -width flag
.It Ic \&:
A target is considered out-of-date if its modification time is less than
those of any of its sources.
Sources for a target accumulate over dependency lines when this operator
is used.
The target is removed if
.Nm
is interrupted.
.It Ic \&!
Targets are always re-created, but not until all sources have been
examined and re-created as necessary.
Sources for a target accumulate over dependency lines when this operator
is used.
The target is removed if
.Nm
is interrupted.
.It Ic \&::
If no sources are specified, the target is always re-created.
Otherwise, a target is considered out-of-date if any of its sources has
been modified more recently than the target.
Sources for a target do not accumulate over dependency lines when this
operator is used.
The target will not be removed if
.Nm
is interrupted.
.El
.Pp
Targets and sources may contain the shell wildcard values
.Ql \&? ,
.Ql * ,
.Ql [] ,
and
.Ql {} .
The values
.Ql \&? ,
.Ql * ,
and
.Ql []
may only be used as part of the final
component of the target or source, and must be used to describe existing
files.
The value
.Ql {}
need not necessarily be used to describe existing files.
Expansion is in directory order, not alphabetically as done in the shell.
.Sh SHELL COMMANDS
Each target may have associated with it one or more lines of shell
commands, normally
used to create the target.
Each of the lines in this script
.Em must
be preceded by a tab.
(For historical reasons, spaces are not accepted.)
While targets can appear in many dependency lines if desired, by
default only one of these rules may be followed by a creation
script.
If the
.Ql Ic \&::
operator is used, however, all rules may include scripts and the
scripts are executed in the order found.
.Pp
Each line is treated as a separate shell command, unless the end of
line is escaped with a backslash
.Pq Ql \e
in which case that line and the next are combined.
.\" The escaped newline is retained and passed to the shell, which
.\" normally ignores it.
.\" However, the tab at the beginning of the following line is removed.
If the first characters of the command are any combination of
.Ql Ic @ ,
.Ql Ic + ,
or
.Ql Ic \- ,
the command is treated specially.
A
.Ql Ic @
causes the command not to be echoed before it is executed.
A
.Ql Ic +
causes the command to be executed even when
.Fl n
is given.
This is similar to the effect of the .MAKE special source,
except that the effect can be limited to a single line of a script.
A
.Ql Ic \-
in compatibility mode
causes any non-zero exit status of the command line to be ignored.
.Pp
When
.Nm
is run in jobs mode with
.Fl j Ar max_jobs ,
the entire script for the target is fed to a
single instance of the shell.
In compatibility (non-jobs) mode, each command is run in a separate process.
If the command contains any shell meta characters
.Pq Ql #=|^(){};&<>*?[]:$`\e\en
it will be passed to the shell; otherwise
.Nm
will attempt direct execution.
If a line starts with
.Ql Ic \-
and the shell has ErrCtl enabled then failure of the command line
will be ignored as in compatibility mode.
Otherwise
.Ql Ic \-
affects the entire job;
the script will stop at the first command line that fails,
but the target will not be deemed to have failed.
.Pp
Makefiles should be written so that the mode of
.Nm
operation does not change their behavior.
For example, any command which needs to use
.Dq cd
or
.Dq chdir
without potentially changing the directory for subsequent commands
should be put in parentheses so it executes in a subshell.
To force the use of one shell, escape the line breaks so as to make
the whole script one command.
For example:
.Bd -literal -offset indent
avoid-chdir-side-effects:
        @echo Building $@ in `pwd`
        @(cd ${.CURDIR} && ${MAKE} $@)
        @echo Back in `pwd`

ensure-one-shell-regardless-of-mode:
        @echo Building $@ in `pwd`; \e
        (cd ${.CURDIR} && ${MAKE} $@); \e
        echo Back in `pwd`
.Ed
.Pp
Since
.Nm
will
.Xr chdir 2
to
.Ql Va .OBJDIR
before executing any targets, each child process
starts with that as its current working directory.
.Sh VARIABLE ASSIGNMENTS
Variables in make are much like variables in the shell, and, by tradition,
consist of all upper-case letters.
.Ss Variable assignment modifiers
The five operators that can be used to assign values to variables are as
follows:
.Bl -tag -width Ds
.It Ic \&=
Assign the value to the variable.
Any previous value is overridden.
.It Ic \&+=
Append the value to the current value of the variable.
.It Ic \&?=
Assign the value to the variable if it is not already defined.
.It Ic \&:=
Assign with expansion, i.e. expand the value before assigning it
to the variable.
Normally, expansion is not done until the variable is referenced.
.Em NOTE :
References to undefined variables are
.Em not
expanded.
This can cause problems when variable modifiers are used.
.It Ic \&!=
Expand the value and pass it to the shell for execution and assign
the result to the variable.
Any newlines in the result are replaced with spaces.
.El
.Pp
Any white-space before the assigned
.Ar value
is removed; if the value is being appended, a single space is inserted
between the previous contents of the variable and the appended value.
.Pp
Variables are expanded by surrounding the variable name with either
curly braces
.Pq Ql {}
or parentheses
.Pq Ql ()
and preceding it with
a dollar sign
.Pq Ql \&$ .
If the variable name contains only a single letter, the surrounding
braces or parentheses are not required.
This shorter form is not recommended.
.Pp
If the variable name contains a dollar, then the name itself is expanded first.
This allows almost arbitrary variable names, however names containing dollar,
braces, parenthesis, or whitespace are really best avoided!
.Pp
If the result of expanding a variable contains a dollar sign
.Pq Ql \&$
the string is expanded again.
.Pp
Variable substitution occurs at three distinct times, depending on where
the variable is being used.
.Bl -enum
.It
Variables in dependency lines are expanded as the line is read.
.It
Variables in shell commands are expanded when the shell command is
executed.
.It
.Dq .for
loop index variables are expanded on each loop iteration.
Note that other variables are not expanded inside loops so
the following example code:
.Bd -literal -offset indent

.Dv .for i in 1 2 3
a+=     ${i}
j=      ${i}
b+=     ${j}
.Dv .endfor

all:
        @echo ${a}
        @echo ${b}

.Ed
will print:
.Bd -literal -offset indent
1 2 3
3 3 3

.Ed
Because while ${a} contains
.Dq 1 2 3
after the loop is executed, ${b}
contains
.Dq ${j} ${j} ${j}
which expands to
.Dq 3 3 3
since after the loop completes ${j} contains
.Dq 3 .
.El
.Ss Variable classes
The four different classes of variables (in order of increasing precedence)
are:
.Bl -tag -width Ds
.It Environment variables
Variables defined as part of
.Nm Ns 's
environment.
.It Global variables
Variables defined in the makefile or in included makefiles.
.It Command line variables
Variables defined as part of the command line.
.It Local variables
Variables that are defined specific to a certain target.
.El
.Pp
Local variables are all built in and their values vary magically from
target to target.
It is not currently possible to define new local variables.
The seven local variables are as follows:
.Bl -tag -width ".ARCHIVE" -offset indent
.It Va .ALLSRC
The list of all sources for this target; also known as
.Ql Va \&\*[Gt] .
.It Va .ARCHIVE
The name of the archive file; also known as
.Ql Va \&! .
.It Va .IMPSRC
In suffix-transformation rules, the name/path of the source from which the
target is to be transformed (the
.Dq implied
source); also known as
.Ql Va \&\*[Lt] .
It is not defined in explicit rules.
.It Va .MEMBER
The name of the archive member; also known as
.Ql Va % .
.It Va .OODATE
The list of sources for this target that were deemed out-of-date; also
known as
.Ql Va \&? .
.It Va .PREFIX
The file prefix of the target, containing only the file portion, no suffix
or preceding directory components; also known as
.Ql Va * .
The suffix must be one of the known suffixes declared with
.Ic .SUFFIXES
or it will not be recognized.
.It Va .TARGET
The name of the target; also known as
.Ql Va @ .
.El
.Pp
The shorter forms
.Ql ( Va \*[Gt] ,
.Ql Va \&! ,
.Ql Va \*[Lt] ,
.Ql Va % ,
.Ql Va \&? ,
.Ql Va * ,
and
.Ql Va @ )
are permitted for backward
compatibility with historical makefiles and legacy POSIX make and are
not recommended.
.Pp
Variants of these variables with the punctuation followed immediately by
.Ql D
or
.Ql F ,
e.g.
.Ql Va $(@D) ,
are legacy forms equivalent to using the
.Ql :H
and
.Ql :T
modifiers.
These forms are accepted for compatibility with
.At V
makefiles and POSIX but are not recommended.
.Pp
Four of the local variables may be used in sources on dependency lines
because they expand to the proper value for each target on the line.
These variables are
.Ql Va .TARGET ,
.Ql Va .PREFIX ,
.Ql Va .ARCHIVE ,
and
.Ql Va .MEMBER .
.Ss Additional built-in variables
In addition,
.Nm
sets or knows about the following variables:
.Bl -tag -width .MAKEOVERRIDES
.It Va \&$
A single dollar sign
.Ql \&$ ,
i.e.
.Ql \&$$
expands to a single dollar
sign.
.It Va .ALLTARGETS
The list of all targets encountered in the Makefile.
If evaluated during
Makefile parsing, lists only those targets encountered thus far.
.It Va .CURDIR
A path to the directory where
.Nm
was executed.
Refer to the description of
.Ql Ev PWD
for more details.
.It Va .INCLUDEDFROMDIR
The directory of the file this Makefile was included from.
.It Va .INCLUDEDFROMFILE
The filename of the file this Makefile was included from.
.It Ev MAKE
The name that
.Nm
was executed with
.Pq Va argv[0] .
For compatibility
.Nm
also sets
.Va .MAKE
with the same value.
The preferred variable to use is the environment variable
.Ev MAKE
because it is more compatible with other versions of
.Nm
and cannot be confused with the special target with the same name.
.It Va .MAKE.ALWAYS_PASS_JOB_QUEUE
Tells
.Nm
whether to pass the descriptors of the job token queue
even if the target is not tagged with
.Ic .MAKE
The default is 
.Ql Pa yes
for backwards compatability with
.Fx 9.0
and earlier.
.It Va .MAKE.DEPENDFILE
Names the makefile (default
.Ql Pa .depend )
from which generated dependencies are read.
.It Va .MAKE.EXPAND_VARIABLES
A boolean that controls the default behavior of the
.Fl V
option.
.It Va .MAKE.EXPORTED
The list of variables exported by
.Nm .
.It Va .MAKE.JOBS
The argument to the
.Fl j
option.
.It Va .MAKE.JOB.PREFIX
If
.Nm
is run with
.Ar j
then output for each target is prefixed with a token
.Ql --- target ---
the first part of which can be controlled via
.Va .MAKE.JOB.PREFIX .
If
.Va .MAKE.JOB.PREFIX
is empty, no token is printed.
.br
For example:
.Li .MAKE.JOB.PREFIX=${.newline}---${.MAKE:T}[${.MAKE.PID}]
would produce tokens like
.Ql ---make[1234] target ---
making it easier to track the degree of parallelism being achieved.
.It Ev MAKEFLAGS
The environment variable
.Ql Ev MAKEFLAGS
may contain anything that
may be specified on
.Nm Ns 's
command line.
Anything specified on
.Nm Ns 's
command line is appended to the
.Ql Ev MAKEFLAGS
variable which is then
entered into the environment for all programs which
.Nm
executes.
.It Va .MAKE.LEVEL
The recursion depth of
.Nm .
The initial instance of
.Nm
will be 0, and an incremented value is put into the environment
to be seen by the next generation.
This allows tests like:
.Li .if ${.MAKE.LEVEL} == 0
to protect things which should only be evaluated in the initial instance of
.Nm .
.It Va .MAKE.MAKEFILE_PREFERENCE
The ordered list of makefile names
(default
.Ql Pa makefile ,
.Ql Pa Makefile )
that
.Nm
will look for.
.It Va .MAKE.MAKEFILES
The list of makefiles read by
.Nm ,
which is useful for tracking dependencies.
Each makefile is recorded only once, regardless of the number of times read.
.It Va .MAKE.MODE
Processed after reading all makefiles.
Can affect the mode that
.Nm
runs in.
It can contain a number of keywords:
.Bl -hang -width ignore-cmd
.It Pa compat
Like
.Fl B ,
puts
.Nm
into "compat" mode.
.It Pa meta
Puts
.Nm
into "meta" mode, where meta files are created for each target
to capture the command run, the output generated and if
.Xr filemon 4
is available, the system calls which are of interest to
.Nm .
The captured output can be very useful when diagnosing errors.
.It Pa curdirOk= Ar bf
Normally
.Nm
will not create .meta files in
.Ql Va .CURDIR .
This can be overridden by setting
.Va bf
to a value which represents True.
.It Pa env
For debugging, it can be useful to inlcude the environment
in the .meta file.
.It Pa verbose
If in "meta" mode, print a clue about the target being built.
This is useful if the build is otherwise running silently.
The message printed the value of:
.Va .MAKE.META.PREFIX .
.It Pa ignore-cmd
Some makefiles have commands which are simply not stable.
This keyword causes them to be ignored for
determining whether a target is out of date in "meta" mode.
See also
.Ic .NOMETA_CMP .
.It Pa silent= Ar bf
If
.Va bf
is True, when a .meta file is created, mark the target
.Ic .SILENT .
.El
.It Va .MAKE.META.BAILIWICK
In "meta" mode, provides a list of prefixes which
match the directories controlled by
.Nm .
If a file that was generated outside of
.Va .OBJDIR
but within said bailiwick is missing,
the current target is considered out-of-date.
.It Va .MAKE.META.CREATED
In "meta" mode, this variable contains a list of all the meta files
updated.
If not empty, it can be used to trigger processing of
.Va .MAKE.META.FILES .
.It Va .MAKE.META.FILES
In "meta" mode, this variable contains a list of all the meta files
used (updated or not).
This list can be used to process the meta files to extract dependency
information.
.It Va .MAKE.META.IGNORE_PATHS
Provides a list of path prefixes that should be ignored;
because the contents are expected to change over time.
The default list includes:
.Ql Pa /dev /etc /proc /tmp /var/run /var/tmp
.It Va .MAKE.META.PREFIX
Defines the message printed for each meta file updated in "meta verbose" mode.
The default value is:
.Dl Building ${.TARGET:H:tA}/${.TARGET:T}
.It Va .MAKEOVERRIDES
This variable is used to record the names of variables assigned to
on the command line, so that they may be exported as part of
.Ql Ev MAKEFLAGS .
This behaviour can be disabled by assigning an empty value to
.Ql Va .MAKEOVERRIDES
within a makefile.
Extra variables can be exported from a makefile
by appending their names to
.Ql Va .MAKEOVERRIDES .
.Ql Ev MAKEFLAGS
is re-exported whenever
.Ql Va .MAKEOVERRIDES
is modified.
.It Va .MAKE.PATH_FILEMON
If
.Nm
was built with
.Xr filemon 4
support, this is set to the path of the device node.
This allows makefiles to test for this support.
.It Va .MAKE.PID
The process-id of
.Nm .
.It Va .MAKE.PPID
The parent process-id of
.Nm .
.It Va MAKE_PRINT_VAR_ON_ERROR
When
.Nm
stops due to an error, it prints its name and the value of
.Ql Va .CURDIR
as well as the value of any variables named in
.Ql Va MAKE_PRINT_VAR_ON_ERROR .
.It Va .newline
This variable is simply assigned a newline character as its value.
This allows expansions using the
.Cm \&:@
modifier to put a newline between
iterations of the loop rather than a space.
For example, the printing of
.Ql Va MAKE_PRINT_VAR_ON_ERROR
could be done as ${MAKE_PRINT_VAR_ON_ERROR:@v@$v='${$v}'${.newline}@}.
.It Va .OBJDIR
A path to the directory where the targets are built.
Its value is determined by trying to
.Xr chdir 2
to the following directories in order and using the first match:
.Bl -enum
.It
.Ev ${MAKEOBJDIRPREFIX}${.CURDIR}
.Pp
(Only if
.Ql Ev MAKEOBJDIRPREFIX
is set in the environment or on the command line.)
.It
.Ev ${MAKEOBJDIR}
.Pp
(Only if
.Ql Ev MAKEOBJDIR
is set in the environment or on the command line.)
.It
.Ev ${.CURDIR} Ns Pa /obj. Ns Ev ${MACHINE}
.It
.Ev ${.CURDIR} Ns Pa /obj
.It
.Pa /usr/obj/ Ns Ev ${.CURDIR}
.It
.Ev ${.CURDIR}
.El
.Pp
Variable expansion is performed on the value before it's used,
so expressions such as
.Dl ${.CURDIR:S,^/usr/src,/var/obj,}
may be used.
This is especially useful with
.Ql Ev MAKEOBJDIR .
.Pp
.Ql Va .OBJDIR
may be modified in the makefile via the special target
.Ql Ic .OBJDIR .
In all cases,
.Nm
will
.Xr chdir 2
to the specified directory if it exists, and set
.Ql Va .OBJDIR
and
.Ql Ev PWD
to that directory before executing any targets.
.
.It Va .PARSEDIR
A path to the directory of the current
.Ql Pa Makefile
being parsed.
.It Va .PARSEFILE
The basename of the current
.Ql Pa Makefile
being parsed.
This variable and
.Ql Va .PARSEDIR
are both set only while the
.Ql Pa Makefiles
are being parsed.
If you want to retain their current values, assign them to a variable
using assignment with expansion:
.Pq Ql Cm \&:= .
.It Va .PATH
A variable that represents the list of directories that
.Nm
will search for files.
The search list should be updated using the target
.Ql Va .PATH
rather than the variable.
.It Ev PWD
Alternate path to the current directory.
.Nm
normally sets
.Ql Va .CURDIR
to the canonical path given by
.Xr getcwd 3 .
However, if the environment variable
.Ql Ev PWD
is set and gives a path to the current directory, then
.Nm
sets
.Ql Va .CURDIR
to the value of
.Ql Ev PWD
instead.
This behaviour is disabled if
.Ql Ev MAKEOBJDIRPREFIX
is set or
.Ql Ev MAKEOBJDIR
contains a variable transform.
.Ql Ev PWD
is set to the value of
.Ql Va .OBJDIR
for all programs which
.Nm
executes.
.It Ev .TARGETS
The list of targets explicitly specified on the command line, if any.
.It Ev VPATH
Colon-separated
.Pq Dq \&:
lists of directories that
.Nm
will search for files.
The variable is supported for compatibility with old make programs only,
use
.Ql Va .PATH
instead.
.El
.Ss Variable modifiers
Variable expansion may be modified to select or modify each word of the
variable (where a
.Dq word
is white-space delimited sequence of characters).
The general format of a variable expansion is as follows:
.Pp
.Dl ${variable[:modifier[:...]]}
.Pp
Each modifier begins with a colon,
which may be escaped with a backslash
.Pq Ql \e .
.Pp
A set of modifiers can be specified via a variable, as follows:
.Pp
.Dl modifier_variable=modifier[:...]
.Dl ${variable:${modifier_variable}[:...]}
.Pp
In this case the first modifier in the modifier_variable does not
start with a colon, since that must appear in the referencing
variable.
If any of the modifiers in the modifier_variable contain a dollar sign
.Pq Ql $ ,
these must be doubled to avoid early expansion.
.Pp
The supported modifiers are:
.Bl -tag -width EEE
.It Cm \&:E
Replaces each word in the variable with its suffix.
.It Cm \&:H
Replaces each word in the variable with everything but the last component.
.It Cm \&:M Ns Ar pattern
Select only those words that match
.Ar pattern .
The standard shell wildcard characters
.Pf ( Ql * ,
.Ql \&? ,
and
.Ql Oo Oc )
may
be used.
The wildcard characters may be escaped with a backslash
.Pq Ql \e .
As a consequence of the way values are split into words, matched,
and then joined, a construct like
.Dl ${VAR:M*}
will normalise the inter-word spacing, removing all leading and
trailing space, and converting multiple consecutive spaces
to single spaces.
.
.It Cm \&:N Ns Ar pattern
This is identical to
.Ql Cm \&:M ,
but selects all words which do not match
.Ar pattern .
.It Cm \&:O
Order every word in variable alphabetically.
To sort words in
reverse order use the
.Ql Cm \&:O:[-1..1]
combination of modifiers.
.It Cm \&:Ox
Randomize words in variable.
The results will be different each time you are referring to the
modified variable; use the assignment with expansion
.Pq Ql Cm \&:=
to prevent such behaviour.
For example,
.Bd -literal -offset indent
LIST=                   uno due tre quattro
RANDOM_LIST=            ${LIST:Ox}
STATIC_RANDOM_LIST:=    ${LIST:Ox}

all:
        @echo "${RANDOM_LIST}"
        @echo "${RANDOM_LIST}"
        @echo "${STATIC_RANDOM_LIST}"
        @echo "${STATIC_RANDOM_LIST}"
.Ed
may produce output similar to:
.Bd -literal -offset indent
quattro due tre uno
tre due quattro uno
due uno quattro tre
due uno quattro tre
.Ed
.It Cm \&:Q
Quotes every shell meta-character in the variable, so that it can be passed
safely through recursive invocations of
.Nm .
.It Cm \&:R
Replaces each word in the variable with everything but its suffix.
.It Cm \&:gmtime
The value is a format string for
.Xr strftime 3 ,
using the current
.Xr gmtime 3 .
.It Cm \&:hash
Compute a 32bit hash of the value and encode it as hex digits.
.It Cm \&:localtime
The value is a format string for
.Xr strftime 3 ,
using the current
.Xr localtime 3 .
.It Cm \&:tA
Attempt to convert variable to an absolute path using
.Xr realpath 3 ,
if that fails, the value is unchanged.
.It Cm \&:tl
Converts variable to lower-case letters.
.It Cm \&:ts Ns Ar c
Words in the variable are normally separated by a space on expansion.
This modifier sets the separator to the character
.Ar c .
If
.Ar c
is omitted, then no separator is used.
The common escapes (including octal numeric codes), work as expected.
.It Cm \&:tu
Converts variable to upper-case letters.
.It Cm \&:tW
Causes the value to be treated as a single word
(possibly containing embedded white space).
See also
.Ql Cm \&:[*] .
.It Cm \&:tw
Causes the value to be treated as a sequence of
words delimited by white space.
See also
.Ql Cm \&:[@] .
.Sm off
.It Cm \&:S No \&/ Ar old_string No \&/ Ar new_string No \&/ Op Cm 1gW
.Sm on
Modify the first occurrence of
.Ar old_string
in the variable's value, replacing it with
.Ar new_string .
If a
.Ql g
is appended to the last slash of the pattern, all occurrences
in each word are replaced.
If a
.Ql 1
is appended to the last slash of the pattern, only the first word
is affected.
If a
.Ql W
is appended to the last slash of the pattern,
then the value is treated as a single word
(possibly containing embedded white space).
If
.Ar old_string
begins with a caret
.Pq Ql ^ ,
.Ar old_string
is anchored at the beginning of each word.
If
.Ar old_string
ends with a dollar sign
.Pq Ql \&$ ,
it is anchored at the end of each word.
Inside
.Ar new_string ,
an ampersand
.Pq Ql \*[Am]
is replaced by
.Ar old_string
(without any
.Ql ^
or
.Ql \&$ ) .
Any character may be used as a delimiter for the parts of the modifier
string.
The anchoring, ampersand and delimiter characters may be escaped with a
backslash
.Pq Ql \e .
.Pp
Variable expansion occurs in the normal fashion inside both
.Ar old_string
and
.Ar new_string
with the single exception that a backslash is used to prevent the expansion
of a dollar sign
.Pq Ql \&$ ,
not a preceding dollar sign as is usual.
.Sm off
.It Cm \&:C No \&/ Ar pattern No \&/ Ar replacement No \&/ Op Cm 1gW
.Sm on
The
.Cm \&:C
modifier is just like the
.Cm \&:S
modifier except that the old and new strings, instead of being
simple strings, are an extended regular expression (see
.Xr regex 3 )
string
.Ar pattern
and an
.Xr ed 1 Ns \-style
string
.Ar replacement .
Normally, the first occurrence of the pattern
.Ar pattern
in each word of the value is substituted with
.Ar replacement .
The
.Ql 1
modifier causes the substitution to apply to at most one word; the
.Ql g
modifier causes the substitution to apply to as many instances of the
search pattern
.Ar pattern
as occur in the word or words it is found in; the
.Ql W
modifier causes the value to be treated as a single word
(possibly containing embedded white space).
Note that
.Ql 1
and
.Ql g
are orthogonal; the former specifies whether multiple words are
potentially affected, the latter whether multiple substitutions can
potentially occur within each affected word.
.Pp
As for the
.Cm \&:S
modifier, the
.Ar pattern
and
.Ar replacement
are subjected to variable expansion before being parsed as
regular expressions.
.It Cm \&:T
Replaces each word in the variable with its last component.
.It Cm \&:u
Remove adjacent duplicate words (like
.Xr uniq 1 ) .
.Sm off
.It Cm \&:\&? Ar true_string Cm \&: Ar false_string
.Sm on
If the variable name (not its value), when parsed as a .if conditional
expression, evaluates to true, return as its value the
.Ar true_string ,
otherwise return the
.Ar false_string .
Since the variable name is used as the expression, \&:\&? must be the
first modifier after the variable name itself - which will, of course,
usually contain variable expansions.
A common error is trying to use expressions like
.Dl ${NUMBERS:M42:?match:no}
which actually tests defined(NUMBERS),
to determine is any words match "42" you need to use something like:
.Dl ${"${NUMBERS:M42}" != \&"\&":?match:no} .
.It Ar :old_string=new_string
This is the
.At V
style variable substitution.
It must be the last modifier specified.
If
.Ar old_string
or
.Ar new_string
do not contain the pattern matching character
.Ar %
then it is assumed that they are
anchored at the end of each word, so only suffixes or entire
words may be replaced.
Otherwise
.Ar %
is the substring of
.Ar old_string
to be replaced in
.Ar new_string .
.Pp
Variable expansion occurs in the normal fashion inside both
.Ar old_string
and
.Ar new_string
with the single exception that a backslash is used to prevent the
expansion of a dollar sign
.Pq Ql \&$ ,
not a preceding dollar sign as is usual.
.Sm off
.It Cm \&:@ Ar temp Cm @ Ar string Cm @
.Sm on
This is the loop expansion mechanism from the OSF Development
Environment (ODE) make.
Unlike
.Cm \&.for
loops expansion occurs at the time of
reference.
Assign
.Ar temp
to each word in the variable and evaluate
.Ar string .
The ODE convention is that
.Ar temp
should start and end with a period.
For example.
.Dl ${LINKS:@.LINK.@${LN} ${TARGET} ${.LINK.}@}
.Pp
However a single character variable is often more readable:
.Dl ${MAKE_PRINT_VAR_ON_ERROR:@v@$v='${$v}'${.newline}@}
.It Cm \&:U Ns Ar newval
If the variable is undefined
.Ar newval
is the value.
If the variable is defined, the existing value is returned.
This is another ODE make feature.
It is handy for setting per-target CFLAGS for instance:
.Dl ${_${.TARGET:T}_CFLAGS:U${DEF_CFLAGS}}
If a value is only required if the variable is undefined, use:
.Dl ${VAR:D:Unewval}
.It Cm \&:D Ns Ar newval
If the variable is defined
.Ar newval
is the value.
.It Cm \&:L
The name of the variable is the value.
.It Cm \&:P
The path of the node which has the same name as the variable
is the value.
If no such node exists or its path is null, then the
name of the variable is used.
In order for this modifier to work, the name (node) must at least have
appeared on the rhs of a dependency.
.Sm off
.It Cm \&:\&! Ar cmd Cm \&!
.Sm on
The output of running
.Ar cmd
is the value.
.It Cm \&:sh
If the variable is non-empty it is run as a command and the output
becomes the new value.
.It Cm \&::= Ns Ar str
The variable is assigned the value
.Ar str
after substitution.
This modifier and its variations are useful in
obscure situations such as wanting to set a variable when shell commands
are being parsed.
These assignment modifiers always expand to
nothing, so if appearing in a rule line by themselves should be
preceded with something to keep
.Nm
happy.
.Pp
The
.Ql Cm \&::
helps avoid false matches with the
.At V
style
.Cm \&:=
modifier and since substitution always occurs the
.Cm \&::=
form is vaguely appropriate.
.It Cm \&::?= Ns Ar str
As for
.Cm \&::=
but only if the variable does not already have a value.
.It Cm \&::+= Ns Ar str
Append
.Ar str
to the variable.
.It Cm \&::!= Ns Ar cmd
Assign the output of
.Ar cmd
to the variable.
.It Cm \&:\&[ Ns Ar range Ns Cm \&]
Selects one or more words from the value,
or performs other operations related to the way in which the
value is divided into words.
.Pp
Ordinarily, a value is treated as a sequence of words
delimited by white space.
Some modifiers suppress this behaviour,
causing a value to be treated as a single word
(possibly containing embedded white space).
An empty value, or a value that consists entirely of white-space,
is treated as a single word.
For the purposes of the
.Ql Cm \&:[]
modifier, the words are indexed both forwards using positive integers
(where index 1 represents the first word),
and backwards using negative integers
(where index \-1 represents the last word).
.Pp
The
.Ar range
is subjected to variable expansion, and the expanded result is
then interpreted as follows:
.Bl -tag -width index
.\" :[n]
.It Ar index
Selects a single word from the value.
.\" :[start..end]
.It Ar start Ns Cm \&.. Ns Ar end
Selects all words from
.Ar start
to
.Ar end ,
inclusive.
For example,
.Ql Cm \&:[2..-1]
selects all words from the second word to the last word.
If
.Ar start
is greater than
.Ar end ,
then the words are output in reverse order.
For example,
.Ql Cm \&:[-1..1]
selects all the words from last to first.
.\" :[*]
.It Cm \&*
Causes subsequent modifiers to treat the value as a single word
(possibly containing embedded white space).
Analogous to the effect of
\&"$*\&"
in Bourne shell.
.\" :[0]
.It 0
Means the same as
.Ql Cm \&:[*] .
.\" :[*]
.It Cm \&@
Causes subsequent modifiers to treat the value as a sequence of words
delimited by white space.
Analogous to the effect of
\&"$@\&"
in Bourne shell.
.\" :[#]
.It Cm \&#
Returns the number of words in the value.
.El \" :[range]
.El
.Sh INCLUDE STATEMENTS, CONDITIONALS AND FOR LOOPS
Makefile inclusion, conditional structures and for loops  reminiscent
of the C programming language are provided in
.Nm .
All such structures are identified by a line beginning with a single
dot
.Pq Ql \&.
character.
Files are included with either
.Cm \&.include Aq Ar file
or
.Cm \&.include Pf \*q Ar file Ns \*q .
Variables between the angle brackets or double quotes are expanded
to form the file name.
If angle brackets are used, the included makefile is expected to be in
the system makefile directory.
If double quotes are used, the including makefile's directory and any
directories specified using the
.Fl I
option are searched before the system
makefile directory.
For compatibility with other versions of
.Nm
.Ql include file ...
is also accepted.
If the include statement is written as
.Cm .-include
or as
.Cm .sinclude
then errors locating and/or opening include files are ignored.
.Pp
Conditional expressions are also preceded by a single dot as the first
character of a line.
The possible conditionals are as follows:
.Bl -tag -width Ds
.It Ic .error Ar message
The message is printed along with the name of the makefile and line number,
then
.Nm
will exit.
.It Ic .export Ar variable ...
Export the specified global variable.
If no variable list is provided, all globals are exported
except for internal variables (those that start with
.Ql \&. ) .
This is not affected by the
.Fl X
flag, so should be used with caution.
For compatibility with other
.Nm
programs
.Ql export variable=value
is also accepted.
.Pp
Appending a variable name to
.Va .MAKE.EXPORTED
is equivalent to exporting a variable.
.It Ic .export-env Ar variable ...
The same as
.Ql .export ,
except that the variable is not appended to
.Va .MAKE.EXPORTED .
This allows exporting a value to the environment which is different from that
used by
.Nm
internally.
.It Ic .info Ar message
The message is printed along with the name of the makefile and line number.
.It Ic .undef Ar variable
Un-define the specified global variable.
Only global variables may be un-defined.
.It Ic .unexport Ar variable ...
The opposite of
.Ql .export .
The specified global
.Va variable
will be removed from
.Va .MAKE.EXPORTED .
If no variable list is provided, all globals are unexported,
and
.Va .MAKE.EXPORTED
deleted.
.It Ic .unexport-env
Unexport all globals previously exported and
clear the environment inherited from the parent.
This operation will cause a memory leak of the original environment,
so should be used sparingly.
Testing for
.Va .MAKE.LEVEL
being 0, would make sense.
Also note that any variables which originated in the parent environment
should be explicitly preserved if desired.
For example:
.Bd -literal -offset indent
.Li .if ${.MAKE.LEVEL} == 0
PATH := ${PATH}
.Li .unexport-env
.Li .export PATH
.Li .endif
.Pp
.Ed
Would result in an environment containing only
.Ql Ev PATH ,
which is the minimal useful environment.
Actually
.Ql Ev .MAKE.LEVEL
will also be pushed into the new environment.
.It Ic .warning Ar message
The message prefixed by
.Ql Pa warning:
is printed along with the name of the makefile and line number.
.It Ic \&.if Oo \&! Oc Ns Ar expression Op Ar operator expression ...
Test the value of an expression.
.It Ic .ifdef Oo \&! Oc Ns Ar variable Op Ar operator variable ...
Test the value of a variable.
.It Ic .ifndef Oo \&! Oc Ns Ar variable Op Ar operator variable ...
Test the value of a variable.
.It Ic .ifmake Oo \&! Oc Ns Ar target Op Ar operator target ...
Test the target being built.
.It Ic .ifnmake Oo \&! Ns Oc Ar target Op Ar operator target ...
Test the target being built.
.It Ic .else
Reverse the sense of the last conditional.
.It Ic .elif Oo \&! Ns Oc Ar expression Op Ar operator expression ...
A combination of
.Ql Ic .else
followed by
.Ql Ic .if .
.It Ic .elifdef Oo \&! Oc Ns Ar variable Op Ar operator variable ...
A combination of
.Ql Ic .else
followed by
.Ql Ic .ifdef .
.It Ic .elifndef Oo \&! Oc Ns Ar variable Op Ar operator variable ...
A combination of
.Ql Ic .else
followed by
.Ql Ic .ifndef .
.It Ic .elifmake Oo \&! Oc Ns Ar target Op Ar operator target ...
A combination of
.Ql Ic .else
followed by
.Ql Ic .ifmake .
.It Ic .elifnmake Oo \&! Oc Ns Ar target Op Ar operator target ...
A combination of
.Ql Ic .else
followed by
.Ql Ic .ifnmake .
.It Ic .endif
End the body of the conditional.
.El
.Pp
The
.Ar operator
may be any one of the following:
.Bl -tag -width "Cm XX"
.It Cm \&|\&|
Logical OR.
.It Cm \&\*[Am]\*[Am]
Logical
.Tn AND ;
of higher precedence than
.Dq \&|\&| .
.El
.Pp
As in C,
.Nm
will only evaluate a conditional as far as is necessary to determine
its value.
Parentheses may be used to change the order of evaluation.
The boolean operator
.Ql Ic \&!
may be used to logically negate an entire
conditional.
It is of higher precedence than
.Ql Ic \&\*[Am]\*[Am] .
.Pp
The value of
.Ar expression
may be any of the following:
.Bl -tag -width defined
.It Ic defined
Takes a variable name as an argument and evaluates to true if the variable
has been defined.
.It Ic make
Takes a target name as an argument and evaluates to true if the target
was specified as part of
.Nm Ns 's
command line or was declared the default target (either implicitly or
explicitly, see
.Va .MAIN )
before the line containing the conditional.
.It Ic empty
Takes a variable, with possible modifiers, and evaluates to true if
the expansion of the variable would result in an empty string.
.It Ic exists
Takes a file name as an argument and evaluates to true if the file exists.
The file is searched for on the system search path (see
.Va .PATH ) .
.It Ic target
Takes a target name as an argument and evaluates to true if the target
has been defined.
.It Ic commands
Takes a target name as an argument and evaluates to true if the target
has been defined and has commands associated with it.
.El
.Pp
.Ar Expression
may also be an arithmetic or string comparison.
Variable expansion is
performed on both sides of the comparison, after which the integral
values are compared.
A value is interpreted as hexadecimal if it is
preceded by 0x, otherwise it is decimal; octal numbers are not supported.
The standard C relational operators are all supported.
If after
variable expansion, either the left or right hand side of a
.Ql Ic ==
or
.Ql Ic "!="
operator is not an integral value, then
string comparison is performed between the expanded
variables.
If no relational operator is given, it is assumed that the expanded
variable is being compared against 0 or an empty string in the case
of a string comparison.
.Pp
When
.Nm
is evaluating one of these conditional expressions, and it encounters
a (white-space separated) word it doesn't recognize, either the
.Dq make
or
.Dq defined
expression is applied to it, depending on the form of the conditional.
If the form is
.Ql Ic .ifdef ,
.Ql Ic .ifndef ,
or
.Ql Ic .if
the
.Dq defined
expression is applied.
Similarly, if the form is
.Ql Ic .ifmake
or
.Ql Ic .ifnmake , the
.Dq make
expression is applied.
.Pp
If the conditional evaluates to true the parsing of the makefile continues
as before.
If it evaluates to false, the following lines are skipped.
In both cases this continues until a
.Ql Ic .else
or
.Ql Ic .endif
is found.
.Pp
For loops are typically used to apply a set of rules to a list of files.
The syntax of a for loop is:
.Pp
.Bl -tag -compact -width Ds
.It Ic \&.for Ar variable Oo Ar variable ... Oc Ic in Ar expression
.It Aq make-rules
.It Ic \&.endfor
.El
.Pp
After the for
.Ic expression
is evaluated, it is split into words.
On each iteration of the loop, one word is taken and assigned to each
.Ic variable ,
in order, and these
.Ic variables
are substituted into the
.Ic make-rules
inside the body of the for loop.
The number of words must come out even; that is, if there are three
iteration variables, the number of words provided must be a multiple
of three.
.Sh COMMENTS
Comments begin with a hash
.Pq Ql \&#
character, anywhere but in a shell
command line, and continue to the end of an unescaped new line.
.Sh SPECIAL SOURCES (ATTRIBUTES)
.Bl -tag -width .IGNOREx
.It Ic .EXEC
Target is never out of date, but always execute commands anyway.
.It Ic .IGNORE
Ignore any errors from the commands associated with this target, exactly
as if they all were preceded by a dash
.Pq Ql \- .
.\" .It Ic .INVISIBLE
.\" XXX
.\" .It Ic .JOIN
.\" XXX
.It Ic .MADE
Mark all sources of this target as being up-to-date.
.It Ic .MAKE
Execute the commands associated with this target even if the
.Fl n
or
.Fl t
options were specified.
Normally used to mark recursive
.Nm Ns s .
.It Ic .META
Create a meta file for the target, even if it is flagged as
.Ic .PHONY ,
.Ic .MAKE ,
or
.Ic .SPECIAL .
Usage in conjunction with
.Ic .MAKE
is the most likely case.
In "meta" mode, the target is out-of-date if the meta file is missing.
.It Ic .NOMETA
Do not create a meta file for the target.
Meta files are also not created for
.Ic .PHONY ,
.Ic .MAKE ,
or
.Ic .SPECIAL
targets.
.It Ic .NOMETA_CMP
Ignore differences in commands when deciding if target is out of date.
This is useful if the command contains a value which always changes.
If the number of commands change, though, the target will still be out of date.
The same effect applies to any command line that uses the variable
.Va .OODATE ,
which can be used for that purpose even when not otherwise needed or desired:
.Bd -literal -offset indent

skip-compare-for-some:
        @echo this will be compared
        @echo this will not ${.OODATE:M.NOMETA_CMP}
        @echo this will also be compared

.Ed
The
.Cm \&:M
pattern suppresses any expansion of the unwanted variable.
.It Ic .NOPATH
Do not search for the target in the directories specified by
.Ic .PATH .
.It Ic .NOTMAIN
Normally
.Nm
selects the first target it encounters as the default target to be built
if no target was specified.
This source prevents this target from being selected.
.It Ic .OPTIONAL
If a target is marked with this attribute and
.Nm
can't figure out how to create it, it will ignore this fact and assume
the file isn't needed or already exists.
.It Ic .PHONY
The target does not
correspond to an actual file; it is always considered to be out of date,
and will not be created with the
.Fl t
option.
Suffix-transformation rules are not applied to
.Ic .PHONY
targets.
.It Ic .PRECIOUS
When
.Nm
is interrupted, it normally removes any partially made targets.
This source prevents the target from being removed.
.It Ic .RECURSIVE
Synonym for
.Ic .MAKE .
.It Ic .SILENT
Do not echo any of the commands associated with this target, exactly
as if they all were preceded by an at sign
.Pq Ql @ .
.It Ic .USE
Turn the target into
.Nm Ns 's
version of a macro.
When the target is used as a source for another target, the other target
acquires the commands, sources, and attributes (except for
.Ic .USE )
of the
source.
If the target already has commands, the
.Ic .USE
target's commands are appended
to them.
.It Ic .USEBEFORE
Exactly like
.Ic .USE ,
but prepend the
.Ic .USEBEFORE
target commands to the target.
.It Ic .WAIT
If
.Ic .WAIT
appears in a dependency line, the sources that precede it are
made before the sources that succeed it in the line.
Since the dependents of files are not made until the file itself
could be made, this also stops the dependents being built unless they
are needed for another branch of the dependency tree.
So given:
.Bd -literal
x: a .WAIT b
        echo x
a:
        echo a
b: b1
        echo b
b1:
        echo b1

.Ed
the output is always
.Ql a ,
.Ql b1 ,
.Ql b ,
.Ql x .
.br
The ordering imposed by
.Ic .WAIT
is only relevant for parallel makes.
.El
.Sh SPECIAL TARGETS
Special targets may not be included with other targets, i.e. they must be
the only target specified.
.Bl -tag -width .BEGINx
.It Ic .BEGIN
Any command lines attached to this target are executed before anything
else is done.
.It Ic .DEFAULT
This is sort of a
.Ic .USE
rule for any target (that was used only as a
source) that
.Nm
can't figure out any other way to create.
Only the shell script is used.
The
.Ic .IMPSRC
variable of a target that inherits
.Ic .DEFAULT Ns 's
commands is set
to the target's own name.
.It Ic .END
Any command lines attached to this target are executed after everything
else is done.
.It Ic .ERROR
Any command lines attached to this target are executed when another target fails.
The
.Ic .ERROR_TARGET
variable is set to the target that failed.
See also
.Ic MAKE_PRINT_VAR_ON_ERROR .
.It Ic .IGNORE
Mark each of the sources with the
.Ic .IGNORE
attribute.
If no sources are specified, this is the equivalent of specifying the
.Fl i
option.
.It Ic .INTERRUPT
If
.Nm
is interrupted, the commands for this target will be executed.
.It Ic .MAIN
If no target is specified when
.Nm
is invoked, this target will be built.
.It Ic .MAKEFLAGS
This target provides a way to specify flags for
.Nm
when the makefile is used.
The flags are as if typed to the shell, though the
.Fl f
option will have
no effect.
.\" XXX: NOT YET!!!!
.\" .It Ic .NOTPARALLEL
.\" The named targets are executed in non parallel mode.
.\" If no targets are
.\" specified, then all targets are executed in non parallel mode.
.It Ic .NOPATH
Apply the
.Ic .NOPATH
attribute to any specified sources.
.It Ic .NOTPARALLEL
Disable parallel mode.
.It Ic .NO_PARALLEL
Synonym for
.Ic .NOTPARALLEL ,
for compatibility with other pmake variants.
.It Ic .OBJDIR
The source is a new value for
.Ql Va .OBJDIR .
If it exists,
.Nm
will
.Xr chdir 2
to it and update the value of
.Ql Va .OBJDIR .
.It Ic .ORDER
The named targets are made in sequence.
This ordering does not add targets to the list of targets to be made.
Since the dependents of a target do not get built until the target itself
could be built, unless
.Ql a
is built by another part of the dependency graph,
the following is a dependency loop:
.Bd -literal
\&.ORDER: b a
b: a
.Ed
.Pp
The ordering imposed by
.Ic .ORDER
is only relevant for parallel makes.
.\" XXX: NOT YET!!!!
.\" .It Ic .PARALLEL
.\" The named targets are executed in parallel mode.
.\" If no targets are
.\" specified, then all targets are executed in parallel mode.
.It Ic .PATH
The sources are directories which are to be searched for files not
found in the current directory.
If no sources are specified, any previously specified directories are
deleted.
If the source is the special
.Ic .DOTLAST
target, then the current working
directory is searched last.
.It Ic .PATH. Ns Va suffix
Like
.Ic .PATH
but applies only to files with a particular suffix.
The suffix must have been previously declared with
.Ic .SUFFIXES .
.It Ic .PHONY
Apply the
.Ic .PHONY
attribute to any specified sources.
.It Ic .PRECIOUS
Apply the
.Ic .PRECIOUS
attribute to any specified sources.
If no sources are specified, the
.Ic .PRECIOUS
attribute is applied to every
target in the file.
.It Ic .SHELL
Sets the shell that
.Nm
will use to execute commands.
The sources are a set of
.Ar field=value
pairs.
.Bl -tag -width hasErrCtls
.It Ar name
This is the minimal specification, used to select one of the builtin
shell specs;
.Ar sh ,
.Ar ksh ,
and
.Ar csh .
.It Ar path
Specifies the path to the shell.
.It Ar hasErrCtl
Indicates whether the shell supports exit on error.
.It Ar check
The command to turn on error checking.
.It Ar ignore
The command to disable error checking.
.It Ar echo
The command to turn on echoing of commands executed.
.It Ar quiet
The command to turn off echoing of commands executed.
.It Ar filter
The output to filter after issuing the
.Ar quiet
command.
It is typically identical to
.Ar quiet .
.It Ar errFlag
The flag to pass the shell to enable error checking.
.It Ar echoFlag
The flag to pass the shell to enable command echoing.
.It Ar newline
The string literal to pass the shell that results in a single newline
character when used outside of any quoting characters.
.El
Example:
.Bd -literal
\&.SHELL: name=ksh path=/bin/ksh hasErrCtl=true \e
        check="set \-e" ignore="set +e" \e
        echo="set \-v" quiet="set +v" filter="set +v" \e
        echoFlag=v errFlag=e newline="'\en'"
.Ed
.It Ic .SILENT
Apply the
.Ic .SILENT
attribute to any specified sources.
If no sources are specified, the
.Ic .SILENT
attribute is applied to every
command in the file.
.It Ic .STALE
This target gets run when a dependency file contains stale entries, having
.Va .ALLSRC
set to the name of that dependency file.
.It Ic .SUFFIXES
Each source specifies a suffix to
.Nm .
If no sources are specified, any previously specified suffixes are deleted.
It allows the creation of suffix-transformation rules.
.Pp
Example:
.Bd -literal
\&.SUFFIXES: .o
\&.c.o:
        cc \-o ${.TARGET} \-c ${.IMPSRC}
.Ed
.El
.Sh ENVIRONMENT
.Nm
uses the following environment variables, if they exist:
.Ev MACHINE ,
.Ev MACHINE_ARCH ,
.Ev MAKE ,
.Ev MAKEFLAGS ,
.Ev MAKEOBJDIR ,
.Ev MAKEOBJDIRPREFIX ,
.Ev MAKESYSPATH ,
.Ev PWD ,
and
.Ev TMPDIR .
.Pp
.Ev MAKEOBJDIRPREFIX
and
.Ev MAKEOBJDIR
may only be set in the environment or on the command line to
.Nm
and not as makefile variables;
see the description of
.Ql Va .OBJDIR
for more details.
.Sh FILES
.Bl -tag -width /usr/share/mk -compact
.It .depend
list of dependencies
.It Makefile
list of dependencies
.It makefile
list of dependencies
.It sys.mk
system makefile
.It /usr/share/mk
system makefile directory
.El
.Sh COMPATIBILITY
The basic make syntax is compatible between different versions of make;
however the special variables, variable modifiers and conditionals are not.
.Ss Older versions
An incomplete list of changes in older versions of
.Nm :
.Pp
The way that .for loop variables are substituted changed after
.Nx 5.0
so that they still appear to be variable expansions.
In particular this stops them being treated as syntax, and removes some
obscure problems using them in .if statements.
.Pp
The way that parallel makes are scheduled changed in
.Nx 4.0
so that .ORDER and .WAIT apply recursively to the dependent nodes.
The algorithms used may change again in the future.
.Ss Other make dialects
Other make dialects (GNU make, SVR4 make, POSIX make, etc.) do not
support most of the features of
.Nm
as described in this manual.
Most notably:
.Bl -bullet -offset indent
.It
The
.Ic .WAIT
and
.Ic .ORDER
declarations and most functionality pertaining to parallelization.
(GNU make supports parallelization but lacks these features needed to
control it effectively.)
.It
Directives, including for loops and conditionals and most of the
forms of include files.
(GNU make has its own incompatible and less powerful syntax for
conditionals.)
.It
All built-in variables that begin with a dot.
.It
Most of the special sources and targets that begin with a dot,
with the notable exception of
.Ic .PHONY ,
.Ic .PRECIOUS ,
and
.Ic .SUFFIXES .
.It
Variable modifiers, except for the
.Dl :old=new
string substitution, which does not portably support globbing with
.Ql %
and historically only works on declared suffixes.
.It
The
.Ic $>
variable even in its short form; most makes support this functionality
but its name varies.
.El
.Pp
Some features are somewhat more portable, such as assignment with
.Ic += ,
.Ic ?= ,
and
.Ic != .
The
.Ic .PATH
functionality is based on an older feature
.Ic VPATH
found in GNU make and many versions of SVR4 make; however,
historically its behavior is too ill-defined (and too buggy) to rely
upon.
.Pp
The
.Ic $@
and
.Ic $<
variables are more or less universally portable, as is the
.Ic $(MAKE)
variable.
Basic use of suffix rules (for files only in the current directory,
not trying to chain transformations together, etc.) is also reasonably
portable.
.Sh SEE ALSO
.Xr mkdep 1
.Sh HISTORY
A
.Nm
command appeared in
.At v7 .
This
.Nm
implementation is based on Adam De Boor's pmake program which was written
for Sprite at Berkeley.
It was designed to be a parallel distributed make running jobs on different
machines using a daemon called
.Dq customs .
.Pp
Historically the target/dependency
.Dq FRC
has been used to FoRCe rebuilding (since the target/dependency
does not exist... unless someone creates an
.Dq FRC
file).
.Sh BUGS
The
.Nm
syntax is difficult to parse without actually acting of the data.
For instance finding the end of a variable use should involve scanning each
the modifiers using the correct terminator for each field.
In many places
.Nm
just counts {} and () in order to find the end of a variable expansion.
.Pp
There is no way of escaping a space character in a filename.