MAKE(1) FreeBSD General Commands Manual MAKE(1)
NAME
make - maintain program dependencies
SYNOPSIS
make [-BeikNnqrSstWwX] [-C directory] [-D variable] [-d flags]
[-f makefile] [-I directory] [-J private] [-j max_jobs]
[-m directory] [-T file] [-V variable] [-v variable]
[variable=value] [target ...]
DESCRIPTION
make 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 -f makefile makefile option is given, make
will try to open `makefile' then `Makefile' in order to find the
specifications. If the file `.depend' exists, it is read (see mkdep(1)).
This manual page is intended as a reference document only. For a more
thorough description of make and makefiles, please refer to PMake - A
Tutorial.
make will prepend the contents of the MAKEFLAGS environment variable to
the command line arguments before parsing them.
The options are as follows:
-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.
-C directory
Change to directory before reading the makefiles or doing
anything else. If multiple -C options are specified, each is
interpreted relative to the previous one: -C / -C etc is
equivalent to -C /etc.
-D variable
Define variable to be 1, in the global scope.
-d [-]flags
Turn on debugging, and specify which portions of make are to
print debugging information. Unless the flags are preceded by
`-' they are added to the 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 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. Flags is one or more of the following:
A Print all possible debugging information; equivalent to
specifying all of the debugging flags.
a Print debugging information about archive searching and
caching.
C Print debugging information about current working
directory.
c Print debugging information about conditional evaluation.
d Print debugging information about directory searching and
caching.
e Print debugging information about failed commands and
targets.
F[+]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 `F'
flag is `+', then the file will be opened in append mode;
otherwise the file will be overwritten. If the file name
is `stdout' or `stderr' then debugging output will be
written to the standard output or standard error output
file descriptors respectively (and the `+' option has no
effect). Otherwise, the output will be written to the
named file. If the file name ends `.%d' then the `%d' is
replaced by the pid.
f Print debugging information about loop evaluation.
g1 Print the input graph before making anything.
g2 Print the input graph after making everything, or before
exiting on error.
g3 Print the input graph before exiting on error.
h Print debugging information about hash table operations.
j Print debugging information about running multiple
shells.
L Turn on lint checks. This will throw errors for variable
assignments that do not parse correctly, at the time of
assignment so the file and line number are available.
l Print commands in Makefiles regardless of whether or not
they are prefixed by `@' or other "quiet" flags. Also
known as "loud" behavior.
M Print debugging information about "meta" mode decisions
about targets.
m Print debugging information about making targets,
including modification dates.
n Don't delete the temporary command scripts created when
running commands. These temporary scripts are created in
the directory referred to by the TMPDIR environment
variable, or in /tmp if TMPDIR is unset or set to the
empty string. The temporary scripts are created by
mkstemp(3), and have names of the form makeXXXXXX. NOTE:
This can create many files in TMPDIR or /tmp, so use with
care.
p Print debugging information about makefile parsing.
s Print debugging information about suffix-transformation
rules.
t Print debugging information about target list
maintenance.
V Force the -V option to print raw values of variables,
overriding the default behavior set via
.MAKE.EXPAND_VARIABLES.
v Print debugging information about variable assignment.
x Run shell commands with -x so the actual commands are
printed as they are executed.
-e Specify that environment variables override macro assignments
within makefiles.
-f makefile
Specify a makefile to read instead of the default `makefile'. If
makefile is `-', standard input is read. Multiple makefiles may
be specified, and are read in the order specified.
-I directory
Specify a directory in which to search for makefiles and included
makefiles. The system makefile directory (or directories, see
the -m option) is automatically included as part of this list.
-i Ignore non-zero exit of shell commands in the makefile.
Equivalent to specifying `-' before each command line in the
makefile.
-J private
This option should not be specified by the user.
When the 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.
-j max_jobs
Specify the maximum number of jobs that make may have running at
any one time. The value is saved in .MAKE.JOBS. Turns
compatibility mode off, unless the 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.
-k Continue processing after errors are encountered, but only on
those targets that do not depend on the target whose creation
caused the error.
-m directory
Specify a directory in which to search for sys.mk and makefiles
included via the <file>-style include statement. The -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 "file"-style include statements (see the -I
option).
If a file or directory name in the -m argument (or the
MAKESYSPATH environment variable) starts with the string ".../"
then make 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 file system. If the search is
successful, then the resulting directory replaces the ".../"
specification in the -m argument. If used, this feature allows
make to easily search in the current source tree for customized
sys.mk files (e.g., by using ".../mk/sys.mk" as an argument).
-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) or the command is prefixed with `+'.
-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.
-q Do not execute any commands, but exit 0 if the specified targets
are up-to-date and 1, otherwise.
-r Do not use the built-in rules specified in the system makefile.
-S Stop processing if an error is encountered. This is the default
behavior and the opposite of -k.
-s Do not echo any commands as they are executed. Equivalent to
specifying `@' before each command line in the makefile.
-T tracefile
When used with the -j flag, append a trace record to tracefile
for each job started and completed.
-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.
-V variable
Print the value of variable. 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. The value printed is extracted from the
global scope after all makefiles have been read. By default, the
raw variable contents (which may include additional unexpanded
variable references) are shown. If variable contains a `$' then
the value will be recursively expanded to its complete resultant
text before printing. The expanded value will also be printed if
.MAKE.EXPAND_VARIABLES is set to true and the -dV option has not
been used to override it. Note that loop-local and target-local
variables, as well as values taken temporarily by global
variables during makefile processing, are not accessible via this
option. The -dv debug mode can be used to see these at the cost
of generating substantial extraneous output.
-v variable
Like -V but the variable is always expanded to its complete
value.
-W Treat any warnings during makefile parsing as errors.
-w Print entering and leaving directory messages, pre and post
processing.
-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 MAKEFLAGS environment variable. This
option may be useful on systems which have a small limit on the
size of command arguments.
variable=value
Set the value of the variable variable to value. Normally, all
values passed on the command line are also exported to sub-makes
in the environment. The -X flag disables this behavior.
Variable assignments should follow options for POSIX
compatibility but no ordering is enforced.
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.
In general, lines may be continued from one line to the next by ending
them with a backslash (`\'). The trailing newline character and initial
whitespace on the following line are compressed into a single space.
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 "depend" on
the sources and are customarily created from them. A target is
considered out-of-date if it does not exist, or if its modification time
is less than that of any of its sources. An out-of-date target will be
re-created, but not until all sources have been examined and themselves
re-created as needed. Three operators may be used:
: Many dependency lines may name this target but only one may have
attached shell commands. All sources named in all dependency lines
are considered together, and if needed the attached shell commands
are run to create or re-create the target. If make is interrupted,
the target is removed.
! The same, but the target is always re-created whether or not it is
out of date.
:: Any dependency line may have attached shell commands, but each one
is handled independently: its sources are considered and the
attached shell commands are run if the target is out of date with
respect to (only) those sources. Thus, different groups of the
attached shell commands may be run depending on the circumstances.
Furthermore, unlike :, for dependency lines with no sources, the
attached shell commands are always run. Also unlike :, the target
will not be removed if make is interrupted.
All dependency lines mentioning a particular target must use the same
operator.
Targets and sources may contain the shell wildcard values `?', `*', `[]',
and `{}'. The values `?', `*', and `[]' 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 `{}' need not necessarily be used to describe
existing files. Expansion is in directory order, not alphabetically as
done in the shell.
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 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 `::' operator is used, however, all rules may include
scripts and the scripts are executed in the order found.
Each line is treated as a separate shell command, unless the end of line
is escaped with a backslash (`\') in which case that line and the next
are combined. If the first characters of the command are any combination
of `@', `+', or `-', the command is treated specially. A `@' causes the
command not to be echoed before it is executed. A `+' causes the command
to be executed even when -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 `-' in compatibility mode causes any non-zero
exit status of the command line to be ignored.
When make is run in jobs mode with -j 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 (`#=|^(){};&<>*?[]:$`\\n') it will be
passed to the shell; otherwise make will attempt direct execution. If a
line starts with `-' and the shell has ErrCtl enabled then failure of the
command line will be ignored as in compatibility mode. Otherwise `-'
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.
Makefiles should be written so that the mode of make operation does not
change their behavior. For example, any command which needs to use "cd"
or "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:
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`; \
(cd ${.CURDIR} && ${MAKE} $@); \
echo Back in `pwd`
Since make will chdir(2) to `.OBJDIR' before executing any targets, each
child process starts with that as its current working directory.
VARIABLE ASSIGNMENTS
Variables in make are much like variables in the shell, and, by
tradition, consist of all upper-case letters.
Variable assignment modifiers
The five operators that can be used to assign values to variables are as
follows:
= Assign the value to the variable. Any previous value is
overridden.
+= Append the value to the current value of the variable.
?= Assign the value to the variable if it is not already defined.
:= Assign with expansion, i.e. expand the value before assigning it
to the variable. Normally, expansion is not done until the
variable is referenced. NOTE: References to undefined variables
are not expanded. This can cause problems when variable
modifiers are used.
!= Expand the value and pass it to the shell for execution and
assign the result to the variable. Any newlines in the result
are replaced with spaces.
Any white-space before the assigned value is removed; if the value is
being appended, a single space is inserted between the previous contents
of the variable and the appended value.
Variables are expanded by surrounding the variable name with either curly
braces (`{}') or parentheses (`()') and preceding it with a dollar sign
(`$'). If the variable name contains only a single letter, the
surrounding braces or parentheses are not required. This shorter form is
not recommended.
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, parentheses, or whitespace are really best
avoided!
If the result of expanding a variable contains a dollar sign (`$') the
string is expanded again.
Variable substitution occurs at three distinct times, depending on where
the variable is being used.
1. Variables in dependency lines are expanded as the line is read.
2. Variables in shell commands are expanded when the shell command is
executed.
3. ".for" loop index variables are expanded on each loop iteration.
Note that other variables are not expanded inside loops so the
following example code:
.for i in 1 2 3
a+= ${i}
j= ${i}
b+= ${j}
.endfor
all:
@echo ${a}
@echo ${b}
will print:
1 2 3
3 3 3
Because while ${a} contains "1 2 3" after the loop is executed, ${b}
contains "${j} ${j} ${j}" which expands to "3 3 3" since after the
loop completes ${j} contains "3".
Variable classes
The four different classes of variables (in order of increasing
precedence) are:
Environment variables
Variables defined as part of make's environment.
Global variables
Variables defined in the makefile or in included makefiles.
Command line variables
Variables defined as part of the command line.
Local variables
Variables that are defined specific to a certain target.
Local variables can be set on a dependency line, if
.MAKE.TARGET_LOCAL_VARIABLES, is not set to `false'. The rest of the
line (which will already have had Global variables expanded), is the
variable value. For example:
COMPILER_WRAPPERS+= ccache distcc icecc
${OBJS}: .MAKE.META.CMP_FILTER=${COMPILER_WRAPPERS:S,^,N,}
Only the targets `${OBJS}' will be impacted by that filter (in "meta"
mode) and simply enabling/disabling any of the wrappers will not render
all of those targets out-of-date.
NOTE: target local variable assignments behave differently in that;
+= Only appends to a previous local assignment for the same
target and variable.
:= Is redundant with respect to Global variables, which have
already been expanded.
The seven built-in local variables are as follows:
.ALLSRC The list of all sources for this target; also known as
`>'.
.ARCHIVE The name of the archive file; also known as `!'.
.IMPSRC In suffix-transformation rules, the name/path of the
source from which the target is to be transformed (the
"implied" source); also known as `<'. It is not defined
in explicit rules.
.MEMBER The name of the archive member; also known as `%'.
.OODATE The list of sources for this target that were deemed out-
of-date; also known as `?'.
.PREFIX The file prefix of the target, containing only the file
portion, no suffix or preceding directory components;
also known as `*'. The suffix must be one of the known
suffixes declared with .SUFFIXES or it will not be
recognized.
.TARGET The name of the target; also known as `@'. For
compatibility with other makes this is an alias for
.ARCHIVE in archive member rules.
The shorter forms (`>', `!', `<', `%', `?', `*', and `@') are permitted
for backward compatibility with historical makefiles and legacy POSIX
make and are not recommended.
Variants of these variables with the punctuation followed immediately by
`D' or `F', e.g. `$(@D)', are legacy forms equivalent to using the `:H'
and `:T' modifiers. These forms are accepted for compatibility with AT&T
System V UNIX makefiles and POSIX but are not recommended.
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 `.TARGET', `.PREFIX', `.ARCHIVE', and `.MEMBER'.
Additional built-in variables
In addition, make sets or knows about the following variables:
$ A single dollar sign `$', i.e. `$$' expands to a single
dollar sign.
.ALLTARGETS The list of all targets encountered in the Makefile. If
evaluated during Makefile parsing, lists only those
targets encountered thus far.
.CURDIR A path to the directory where make was executed. Refer
to the description of `PWD' for more details.
.INCLUDEDFROMDIR
The directory of the file this Makefile was included
from.
.INCLUDEDFROMFILE
The filename of the file this Makefile was included from.
MAKE The name that make was executed with (argv[0]). For
compatibility make also sets .MAKE with the same value.
The preferred variable to use is the environment variable
MAKE because it is more compatible with other versions of
make and cannot be confused with the special target with
the same name.
.MAKE.ALWAYS_PASS_JOB_QUEUE
Tells make whether to pass the descriptors of the job
token queue even if the target is not tagged with .MAKE
The default is `yes' for backwards compatability with
FreeBSD 9.0 and earlier.
.MAKE.DEPENDFILE
Names the makefile (default `.depend') from which
generated dependencies are read.
.MAKE.EXPAND_VARIABLES
A boolean that controls the default behavior of the -V
option. If true, variable values printed with -V are
fully expanded; if false, the raw variable contents
(which may include additional unexpanded variable
references) are shown.
.MAKE.EXPORTED The list of variables exported by make.
.MAKE.JOBS The argument to the -j option.
.MAKE.JOB.PREFIX
If make is run with j then output for each target is
prefixed with a token `--- target ---' the first part of
which can be controlled via .MAKE.JOB.PREFIX. If
.MAKE.JOB.PREFIX is empty, no token is printed.
For example:
.MAKE.JOB.PREFIX=${.newline}---${.MAKE:T}[${.MAKE.PID}]
would produce tokens like `---make[1234] target ---'
making it easier to track the degree of parallelism being
achieved.
.MAKE.TARGET_LOCAL_VARIABLES
If set to `false', apparent variable assignments in
dependency lines are treated as normal sources.
MAKEFLAGS The environment variable `MAKEFLAGS' may contain anything
that may be specified on make's command line. Anything
specified on make's command line is appended to the
`MAKEFLAGS' variable which is then entered into the
environment for all programs which make executes.
.MAKE.LEVEL The recursion depth of make. The initial instance of
make will be 0, and an incremented value is put into the
environment to be seen by the next generation. This
allows tests like: .if ${.MAKE.LEVEL} == 0 to protect
things which should only be evaluated in the initial
instance of make.
.MAKE.MAKEFILE_PREFERENCE
The ordered list of makefile names (default `makefile',
`Makefile') that make will look for.
.MAKE.MAKEFILES
The list of makefiles read by make, which is useful for
tracking dependencies. Each makefile is recorded only
once, regardless of the number of times read.
.MAKE.MODE Processed after reading all makefiles. Can affect the
mode that make runs in. It can contain a number of
keywords:
compat Like -B, puts make into "compat"
mode.
meta Puts make into "meta" mode, where
meta files are created for each
target to capture the command run,
the output generated and if
filemon(4) is available, the system
calls which are of interest to make.
The captured output can be very
useful when diagnosing errors.
curdirOk= bf Normally make will not create .meta
files in `.CURDIR'. This can be
overridden by setting bf to a value
which represents True.
missing-meta= bf If bf is True, then a missing .meta
file makes the target out-of-date.
missing-filemon= bf If bf is True, then missing filemon
data makes the target out-of-date.
nofilemon Do not use filemon(4).
env For debugging, it can be useful to
include the environment in the .meta
file.
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:
.MAKE.META.PREFIX.
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
.NOMETA_CMP.
silent= bf If bf is True, when a .meta file is
created, mark the target .SILENT.
.MAKE.META.BAILIWICK
In "meta" mode, provides a list of prefixes which match
the directories controlled by make. If a file that was
generated outside of .OBJDIR but within said bailiwick is
missing, the current target is considered out-of-date.
.MAKE.META.CMP_FILTER
In "meta" mode, it can (very rarely!) be useful to filter
command lines before comparison. This variable can be
set to a set of modifiers that will be applied to each
line of the old and new command that differ, if the
filtered commands still differ, the target is considered
out-of-date.
.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 .MAKE.META.FILES.
.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.
.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: `/dev /etc /proc /tmp /var/run
/var/tmp'
.MAKE.META.IGNORE_PATTERNS
Provides a list of patterns to match against pathnames.
Ignore any that match.
.MAKE.META.IGNORE_FILTER
Provides a list of variable modifiers to apply to each
pathname. Ignore if the expansion is an empty string.
.MAKE.META.PREFIX
Defines the message printed for each meta file updated in
"meta verbose" mode. The default value is:
Building ${.TARGET:H:tA}/${.TARGET:T}
.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 `MAKEFLAGS'. This behavior can be
disabled by assigning an empty value to `.MAKEOVERRIDES'
within a makefile. Extra variables can be exported from
a makefile by appending their names to `.MAKEOVERRIDES'.
`MAKEFLAGS' is re-exported whenever `.MAKEOVERRIDES' is
modified.
.MAKE.PATH_FILEMON
If make was built with filemon(4) support, this is set to
the path of the device node. This allows makefiles to
test for this support.
.MAKE.PID The process-id of make.
.MAKE.PPID The parent process-id of make.
.MAKE.SAVE_DOLLARS
value should be a boolean that controls whether `$$' are
preserved when doing `:=' assignments. The default is
false, for backwards compatibility. Set to true for
compatability with other makes. If set to false, `$$'
becomes `$' per normal evaluation rules.
.MAKE.UID The user-id running make.
.MAKE.GID The group-id running make.
MAKE_PRINT_VAR_ON_ERROR
When make stops due to an error, it sets `.ERROR_TARGET'
to the name of the target that failed, `.ERROR_CMD' to
the commands of the failed target, and in "meta" mode, it
also sets `.ERROR_CWD' to the getcwd(3), and
`.ERROR_META_FILE' to the path of the meta file (if any)
describing the failed target. It then prints its name
and the value of `.CURDIR' as well as the value of any
variables named in `MAKE_PRINT_VAR_ON_ERROR'.
.newline This variable is simply assigned a newline character as
its value. This allows expansions using the :@ modifier
to put a newline between iterations of the loop rather
than a space. For example, the printing of
`MAKE_PRINT_VAR_ON_ERROR' could be done as
${MAKE_PRINT_VAR_ON_ERROR:@v@$v='${$v}'${.newline}@}.
.OBJDIR A path to the directory where the targets are built. Its
value is determined by trying to chdir(2) to the
following directories in order and using the first match:
1. ${MAKEOBJDIRPREFIX}${.CURDIR}
(Only if `MAKEOBJDIRPREFIX' is set in the
environment or on the command line.)
2. ${MAKEOBJDIR}
(Only if `MAKEOBJDIR' is set in the environment or
on the command line.)
3. ${.CURDIR}/obj.${MACHINE}
4. ${.CURDIR}/obj
5. /usr/obj/${.CURDIR}
6. ${.CURDIR}
Variable expansion is performed on the value before it's
used, so expressions such as
${.CURDIR:S,^/usr/src,/var/obj,}
may be used. This is especially useful with
`MAKEOBJDIR'.
`.OBJDIR' may be modified in the makefile via the special
target `.OBJDIR'. In all cases, make will chdir(2) to
the specified directory if it exists, and set `.OBJDIR'
and `PWD' to that directory before executing any targets.
Except in the case of an explicit `.OBJDIR' target, make
will check that the specified directory is writable and
ignore it if not. This check can be skipped by setting
the environment variable `MAKE_OBJDIR_CHECK_WRITABLE' to
"no".
.PARSEDIR A path to the directory of the current `Makefile' being
parsed.
.PARSEFILE The basename of the current `Makefile' being parsed.
This variable and `.PARSEDIR' are both set only while the
`Makefiles' are being parsed. If you want to retain
their current values, assign them to a variable using
assignment with expansion: (`:=').
.PATH A variable that represents the list of directories that
make will search for files. The search list should be
updated using the target `.PATH' rather than the
variable.
PWD Alternate path to the current directory. make normally
sets `.CURDIR' to the canonical path given by getcwd(3).
However, if the environment variable `PWD' is set and
gives a path to the current directory, then make sets
`.CURDIR' to the value of `PWD' instead. This behavior
is disabled if `MAKEOBJDIRPREFIX' is set or `MAKEOBJDIR'
contains a variable transform. `PWD' is set to the value
of `.OBJDIR' for all programs which make executes.
.SHELL The pathname of the shell used to run target scripts. It
is read-only.
.SUFFIXES The list of known suffixes. It is read-only.
.TARGETS The list of targets explicitly specified on the command
line, if any.
VPATH Colon-separated (":") lists of directories that make will
search for files. The variable is supported for
compatibility with old make programs only, use `.PATH'
instead.
Variable modifiers
Variable expansion may be modified to select or modify each word of the
variable (where a "word" is white-space delimited sequence of
characters). The general format of a variable expansion is as follows:
${variable[:modifier[:...]]}
Each modifier begins with a colon, which may be escaped with a backslash
(`\').
A set of modifiers can be specified via a variable, as follows:
modifier_variable=modifier[:...]
${variable:${modifier_variable}[:...]}
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 (`$'),
these must be doubled to avoid early expansion.
The supported modifiers are:
:E Replaces each word in the variable with its suffix.
:H Replaces each word in the variable with everything but the last
component.
:Mpattern
Selects only those words that match pattern. The standard shell
wildcard characters (`*', `?', and `[]') may be used. The wildcard
characters may be escaped with a backslash (`\'). As a consequence
of the way values are split into words, matched, and then joined, a
construct like
${VAR:M*}
will normalize the inter-word spacing, removing all leading and
trailing space, and converting multiple consecutive spaces to single
spaces.
:Npattern
This is identical to `:M', but selects all words which do not match
pattern.
:O Orders every word in variable alphabetically.
:On Orders every word in variable numerically. A number followed by one
of `k', `M' or `G' is multiplied by the appropriate factor (1024
(k), 1048576 (M), or 1073741824 (G)). Both upper- and lower-case
letters are accepted.
:Or Orders every word in variable in reverse alphabetical order.
:Orn
Orders every word in variable in reverse numerical order.
:Ox Shuffles the words in variable. The results will be different each
time you are referring to the modified variable; use the assignment
with expansion (`:=') to prevent such behavior. For example,
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}"
may produce output similar to:
quattro due tre uno
tre due quattro uno
due uno quattro tre
due uno quattro tre
:Q Quotes every shell meta-character in the variable, so that it can be
passed safely to the shell.
:q Quotes every shell meta-character in the variable, and also doubles
`$' characters so that it can be passed safely through recursive
invocations of make. This is equivalent to: `:S/\$/&&/g:Q'.
:R Replaces each word in the variable with everything but its suffix.
:range[=count]
The value is an integer sequence representing the words of the
original value, or the supplied count.
:gmtime[=utc]
The value is a format string for strftime(3), using gmtime(3). If a
utc value is not provided or is 0, the current time is used.
:hash
Computes a 32-bit hash of the value and encode it as hex digits.
:localtime[=utc]
The value is a format string for strftime(3), using localtime(3).
If a utc value is not provided or is 0, the current time is used.
:tA Attempts to convert variable to an absolute path using realpath(3),
if that fails, the value is unchanged.
:tl Converts variable to lower-case letters.
:tsc
Words in the variable are normally separated by a space on
expansion. This modifier sets the separator to the character c. If
c is omitted, then no separator is used. The common escapes
(including octal numeric codes) work as expected.
:tu Converts variable to upper-case letters.
:tW Causes the value to be treated as a single word (possibly containing
embedded white space). See also `:[*]'.
:tw Causes the value to be treated as a sequence of words delimited by
white space. See also `:[@]'.
:S/old_string/new_string/[1gW]
Modifies the first occurrence of old_string in each word of the
variable's value, replacing it with new_string. If a `g' is
appended to the last delimiter of the pattern, all occurrences in
each word are replaced. If a `1' is appended to the last delimiter
of the pattern, only the first occurrence is affected. If a `W' is
appended to the last delimiter of the pattern, then the value is
treated as a single word (possibly containing embedded white space).
If old_string begins with a caret (`^'), old_string is anchored at
the beginning of each word. If old_string ends with a dollar sign
(`$'), it is anchored at the end of each word. Inside new_string,
an ampersand (`&') is replaced by old_string (without any `^' or
`$'). 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 (`\').
Variable expansion occurs in the normal fashion inside both
old_string and new_string with the single exception that a backslash
is used to prevent the expansion of a dollar sign (`$'), not a
preceding dollar sign as is usual.
:C/pattern/replacement/[1gW]
The :C modifier is just like the :S modifier except that the old and
new strings, instead of being simple strings, are an extended
regular expression (see regex(3)) string pattern and an ed(1)-style
string replacement. Normally, the first occurrence of the pattern
pattern in each word of the value is substituted with replacement.
The `1' modifier causes the substitution to apply to at most one
word; the `g' modifier causes the substitution to apply to as many
instances of the search pattern pattern as occur in the word or
words it is found in; the `W' modifier causes the value to be
treated as a single word (possibly containing embedded white space).
As for the :S modifier, the pattern and replacement are subjected to
variable expansion before being parsed as regular expressions.
:T Replaces each word in the variable with its last path component.
:u Removes adjacent duplicate words (like uniq(1)).
:?true_string:false_string
If the variable name (not its value), when parsed as a .if
conditional expression, evaluates to true, return as its value the
true_string, otherwise return the 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
${NUMBERS:M42:?match:no}
which actually tests defined(NUMBERS), to determine if any words
match "42" you need to use something like:
${"${NUMBERS:M42}" != "":?match:no}.
:old_string=new_string
This is the AT&T System V UNIX style variable substitution. It must
be the last modifier specified. If old_string or new_string do not
contain the pattern matching character % then it is assumed that
they are anchored at the end of each word, so only suffixes or
entire words may be replaced. Otherwise % is the substring of
old_string to be replaced in new_string. If only old_string
contains the pattern matching character %, and old_string matches,
then the result is the new_string. If only the new_string contains
the pattern matching character %, then it is not treated specially
and it is printed as a literal % on match. If there is more than
one pattern matching character (%) in either the new_string or
old_string, only the first instance is treated specially (as the
pattern character); all subsequent instances are treated as regular
characters.
Variable expansion occurs in the normal fashion inside both
old_string and new_string with the single exception that a backslash
is used to prevent the expansion of a dollar sign (`$'), not a
preceding dollar sign as is usual.
:@temp@string@
This is the loop expansion mechanism from the OSF Development
Environment (ODE) make. Unlike .for loops, expansion occurs at the
time of reference. Assigns temp to each word in the variable and
evaluates string. The ODE convention is that temp should start and
end with a period. For example.
${LINKS:@.LINK.@${LN} ${TARGET} ${.LINK.}@}
However a single character variable is often more readable:
${MAKE_PRINT_VAR_ON_ERROR:@v@$v='${$v}'${.newline}@}
:_[=var]
Saves the current variable value in `$_' or the named var for later
reference. Example usage:
M_cmpv.units = 1 1000 1000000
M_cmpv = S,., ,g:_:range:@i@+ $${_:[-$$i]} \
\* $${M_cmpv.units:[$$i]}@:S,^,expr 0 ,1:sh
.if ${VERSION:${M_cmpv}} < ${3.1.12:L:${M_cmpv}}
Here `$_' is used to save the result of the `:S' modifier which is
later referenced using the index values from `:range'.
:Unewval
If the variable is undefined, 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:
${_${.TARGET:T}_CFLAGS:U${DEF_CFLAGS}}
If a value is only required if the variable is undefined, use:
${VAR:D:Unewval}
:Dnewval
If the variable is defined, newval is the value.
:L The name of the variable is the value.
: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.
:!cmd!
The output of running cmd is the value.
:sh If the variable is non-empty it is run as a command and the output
becomes the new value.
::=str
The variable is assigned the value 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 make happy.
The `::' helps avoid false matches with the AT&T System V UNIX style
:= modifier and since substitution always occurs the ::= form is
vaguely appropriate.
::?=str
As for ::= but only if the variable does not already have a value.
::+=str
Append str to the variable.
::!=cmd
Assign the output of cmd to the variable.
:[range]
Selects one or more words from the value, or performs other
operations related to the way in which the value is divided into
words.
Ordinarily, a value is treated as a sequence of words delimited by
white space. Some modifiers suppress this behavior, 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 `:[]'
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).
The range is subjected to variable expansion, and the expanded
result is then interpreted as follows:
index Selects a single word from the value.
start..end
Selects all words from start to end, inclusive. For example,
`:[2..-1]' selects all words from the second word to the last
word. If start is greater than end, then the words are
output in reverse order. For example, `:[-1..1]' selects all
the words from last to first. If the list is already
ordered, then this effectively reverses the list, but it is
more efficient to use `:Or' instead of `:O:[-1..1]'.
* 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 Means the same as `:[*]'.
@ Causes subsequent modifiers to treat the value as a sequence
of words delimited by white space. Analogous to the effect
of "$@" in Bourne shell.
# Returns the number of words in the value.
INCLUDE STATEMENTS, CONDITIONALS AND FOR LOOPS
Makefile inclusion, conditional structures and for loops reminiscent of
the C programming language are provided in make. All such structures are
identified by a line beginning with a single dot (`.') character. Files
are included with either .include <file> or .include "file". 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 -I
option are searched before the system makefile directory. For
compatibility with other versions of make `include file ...' is also
accepted.
If the include statement is written as .-include or as .sinclude then
errors locating and/or opening include files are ignored.
If the include statement is written as .dinclude not only are errors
locating and/or opening include files ignored, but stale dependencies
within the included file will be ignored just like .MAKE.DEPENDFILE.
Conditional expressions are also preceded by a single dot as the first
character of a line. The possible conditionals are as follows:
.error message
The message is printed along with the name of the makefile and
line number, then make will exit immediately.
.export variable ...
Export the specified global variable. If no variable list is
provided, all globals are exported except for internal variables
(those that start with `.'). This is not affected by the -X
flag, so should be used with caution. For compatibility with
other make programs `export variable=value' is also accepted.
Appending a variable name to .MAKE.EXPORTED is equivalent to
exporting a variable.
.export-env variable ...
The same as `.export', except that the variable is not appended
to .MAKE.EXPORTED. This allows exporting a value to the
environment which is different from that used by make internally.
.export-literal variable ...
The same as `.export-env', except that variables in the value are
not expanded.
.info message
The message is printed along with the name of the makefile and
line number.
.undef variable ...
Un-define the specified global variables. Only global variables
can be un-defined.
.unexport variable ...
The opposite of `.export'. The specified global variable will be
removed from .MAKE.EXPORTED. If no variable list is provided,
all globals are unexported, and .MAKE.EXPORTED deleted.
.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 .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:
.if ${.MAKE.LEVEL} == 0
PATH := ${PATH}
.unexport-env
.export PATH
.endif
Would result in an environment containing only `PATH', which is
the minimal useful environment. Actually `.MAKE.LEVEL' will also
be pushed into the new environment.
.warning message
The message prefixed by `warning:' is printed along with the name
of the makefile and line number.
.if [!]expression [operator expression ...]
Test the value of an expression.
.ifdef [!]variable [operator variable ...]
Test the value of a variable.
.ifndef [!]variable [operator variable ...]
Test the value of a variable.
.ifmake [!]target [operator target ...]
Test the target being built.
.ifnmake [!] target [operator target ...]
Test the target being built.
.else Reverse the sense of the last conditional.
.elif [!] expression [operator expression ...]
A combination of `.else' followed by `.if'.
.elifdef [!]variable [operator variable ...]
A combination of `.else' followed by `.ifdef'.
.elifndef [!]variable [operator variable ...]
A combination of `.else' followed by `.ifndef'.
.elifmake [!]target [operator target ...]
A combination of `.else' followed by `.ifmake'.
.elifnmake [!]target [operator target ...]
A combination of `.else' followed by `.ifnmake'.
.endif End the body of the conditional.
The operator may be any one of the following:
|| Logical OR.
&& Logical AND; of higher precedence than "||".
As in C, make 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 `!' may be used to logically negate an
entire conditional. It is of higher precedence than `&&'.
The value of expression may be any of the following:
defined Takes a variable name as an argument and evaluates to true if
the variable has been defined.
make Takes a target name as an argument and evaluates to true if the
target was specified as part of make's command line or was
declared the default target (either implicitly or explicitly,
see .MAIN) before the line containing the conditional.
empty Takes a variable, with possible modifiers, and evaluates to true
if the expansion of the variable would result in an empty
string.
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 .PATH).
target Takes a target name as an argument and evaluates to true if the
target has been defined.
commands
Takes a target name as an argument and evaluates to true if the
target has been defined and has commands associated with it.
Expression may also be an arithmetic or string comparison. Variable
expansion is performed on both sides of the comparison, after which the
numerical 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 `==' or
`!=' operator is not a numerical 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.
When make is evaluating one of these conditional expressions, and it
encounters a (white-space separated) word it doesn't recognize, either
the "make" or "defined" expression is applied to it, depending on the
form of the conditional. If the form is `.ifdef', `.ifndef', or `.if'
the "defined" expression is applied. Similarly, if the form is `.ifmake'
or `.ifnmake', the "make" expression is applied.
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 `.else' or `.endif' is
found.
For loops are typically used to apply a set of rules to a list of files.
The syntax of a for loop is:
.for variable [variable ...] in expression
<make-lines>
.endfor
After the for expression is evaluated, it is split into words. On each
iteration of the loop, one word is taken and assigned to each variable,
in order, and these variables are substituted into the make-lines 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.
COMMENTS
Comments begin with a hash (`#') character, anywhere but in a shell
command line, and continue to the end of an unescaped new line.
SPECIAL SOURCES (ATTRIBUTES)
.EXEC Target is never out of date, but always execute commands
anyway.
.IGNORE Ignore any errors from the commands associated with this
target, exactly as if they all were preceded by a dash (`-').
.MADE Mark all sources of this target as being up-to-date.
.MAKE Execute the commands associated with this target even if the -n
or -t options were specified. Normally used to mark recursive
makes.
.META Create a meta file for the target, even if it is flagged as
.PHONY, .MAKE, or .SPECIAL. Usage in conjunction with .MAKE is
the most likely case. In "meta" mode, the target is out-of-
date if the meta file is missing.
.NOMETA Do not create a meta file for the target. Meta files are also
not created for .PHONY, .MAKE, or .SPECIAL targets.
.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 .OODATE, which can be
used for that purpose even when not otherwise needed or
desired:
skip-compare-for-some:
@echo this will be compared
@echo this will not ${.OODATE:M.NOMETA_CMP}
@echo this will also be compared
The :M pattern suppresses any expansion of the unwanted
variable.
.NOPATH Do not search for the target in the directories specified by
.PATH.
.NOTMAIN Normally make 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.
.OPTIONAL
If a target is marked with this attribute and make can't figure
out how to create it, it will ignore this fact and assume the
file isn't needed or already exists.
.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
-t option. Suffix-transformation rules are not applied to
.PHONY targets.
.PRECIOUS
When make is interrupted, it normally removes any partially
made targets. This source prevents the target from being
removed.
.RECURSIVE
Synonym for .MAKE.
.SILENT Do not echo any of the commands associated with this target,
exactly as if they all were preceded by an at sign (`@').
.USE Turn the target into make'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
.USE) of the source. If the target already has commands, the
.USE target's commands are appended to them.
.USEBEFORE
Exactly like .USE, but prepend the .USEBEFORE target commands
to the target.
.WAIT If .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:
x: a .WAIT b
echo x
a:
echo a
b: b1
echo b
b1:
echo b1
the output is always `a', `b1', `b', `x'.
The ordering imposed by .WAIT is only relevant for parallel
makes.
SPECIAL TARGETS
Special targets may not be included with other targets, i.e. they must be
the only target specified.
.BEGIN Any command lines attached to this target are executed before
anything else is done.
.DEFAULT
This is sort of a .USE rule for any target (that was used only
as a source) that make can't figure out any other way to create.
Only the shell script is used. The .IMPSRC variable of a target
that inherits .DEFAULT's commands is set to the target's own
name.
.DELETE_ON_ERROR
If this target is present in the makefile, it globally causes
make to delete targets whose commands fail. (By default, only
targets whose commands are interrupted during execution are
deleted. This is the historical behavior.) This setting can be
used to help prevent half-finished or malformed targets from
being left around and corrupting future rebuilds.
.END Any command lines attached to this target are executed after
everything else is done.
.ERROR Any command lines attached to this target are executed when
another target fails. The .ERROR_TARGET variable is set to the
target that failed. See also MAKE_PRINT_VAR_ON_ERROR.
.IGNORE Mark each of the sources with the .IGNORE attribute. If no
sources are specified, this is the equivalent of specifying the
-i option.
.INTERRUPT
If make is interrupted, the commands for this target will be
executed.
.MAIN If no target is specified when make is invoked, this target will
be built.
.MAKEFLAGS
This target provides a way to specify flags for make when the
makefile is used. The flags are as if typed to the shell,
though the -f option will have no effect.
.NOPATH Apply the .NOPATH attribute to any specified sources.
.NOTPARALLEL
Disable parallel mode.
.NO_PARALLEL
Synonym for .NOTPARALLEL, for compatibility with other pmake
variants.
.OBJDIR The source is a new value for `.OBJDIR'. If it exists, make
will chdir(2) to it and update the value of `.OBJDIR'.
.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 `a' is built by another part of the
dependency graph, the following is a dependency loop:
.ORDER: b a
b: a
The ordering imposed by .ORDER is only relevant for parallel
makes.
.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 .DOTLAST target, then the current
working directory is searched last.
.PATH.suffix
Like .PATH but applies only to files with a particular suffix.
The suffix must have been previously declared with .SUFFIXES.
.PHONY Apply the .PHONY attribute to any specified sources.
.PRECIOUS
Apply the .PRECIOUS attribute to any specified sources. If no
sources are specified, the .PRECIOUS attribute is applied to
every target in the file.
.SHELL Sets the shell that make will use to execute commands. The
sources are a set of field=value pairs.
name This is the minimal specification, used to select
one of the built-in shell specs; sh, ksh, and csh.
path Specifies the path to the shell.
hasErrCtl Indicates whether the shell supports exit on error.
check The command to turn on error checking.
ignore The command to disable error checking.
echo The command to turn on echoing of commands executed.
quiet The command to turn off echoing of commands
executed.
filter The output to filter after issuing the quiet
command. It is typically identical to quiet.
errFlag The flag to pass the shell to enable error checking.
echoFlag The flag to pass the shell to enable command
echoing.
newline The string literal to pass the shell that results in
a single newline character when used outside of any
quoting characters.
Example:
.SHELL: name=ksh path=/bin/ksh hasErrCtl=true \
check="set -e" ignore="set +e" \
echo="set -v" quiet="set +v" filter="set +v" \
echoFlag=v errFlag=e newline="'\n'"
.SILENT Apply the .SILENT attribute to any specified sources. If no
sources are specified, the .SILENT attribute is applied to every
command in the file.
.STALE This target gets run when a dependency file contains stale
entries, having .ALLSRC set to the name of that dependency file.
.SUFFIXES
Each source specifies a suffix to make. If no sources are
specified, any previously specified suffixes are deleted. It
allows the creation of suffix-transformation rules.
Example:
.SUFFIXES: .o
.c.o:
cc -o ${.TARGET} -c ${.IMPSRC}
ENVIRONMENT
make uses the following environment variables, if they exist: MACHINE,
MACHINE_ARCH, MAKE, MAKEFLAGS, MAKEOBJDIR, MAKEOBJDIRPREFIX, MAKESYSPATH,
PWD, and TMPDIR.
MAKEOBJDIRPREFIX and MAKEOBJDIR may only be set in the environment or on
the command line to make and not as makefile variables; see the
description of `.OBJDIR' for more details.
FILES
.depend list of dependencies
Makefile list of dependencies
makefile list of dependencies
sys.mk system makefile
/usr/share/mk system makefile directory
COMPATIBILITY
The basic make syntax is compatible between different versions of make;
however the special variables, variable modifiers and conditionals are
not.
Older versions
An incomplete list of changes in older versions of make:
The way that .for loop variables are substituted changed after NetBSD 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.
The way that parallel makes are scheduled changed in NetBSD 4.0 so that
.ORDER and .WAIT apply recursively to the dependent nodes. The
algorithms used may change again in the future.
Other make dialects
Other make dialects (GNU make, SVR4 make, POSIX make, etc.) do not
support most of the features of make as described in this manual. Most
notably:
• The .WAIT and .ORDER declarations and most functionality
pertaining to parallelization. (GNU make supports
parallelization but lacks these features needed to control it
effectively.)
• 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.)
• All built-in variables that begin with a dot.
• Most of the special sources and targets that begin with a dot,
with the notable exception of .PHONY, .PRECIOUS, and .SUFFIXES.
• Variable modifiers, except for the
:old=new
string substitution, which does not portably support globbing
with `%' and historically only works on declared suffixes.
• The $> variable even in its short form; most makes support this
functionality but its name varies.
Some features are somewhat more portable, such as assignment with +=, ?=,
and !=. The .PATH functionality is based on an older feature 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.
The $@ and $< variables are more or less universally portable, as is the
$(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.
SEE ALSO
mkdep(1), style.Makefile(5)
HISTORY
A make command appeared in Version 7 AT&T UNIX. This make 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 "customs".
Historically the target/dependency "FRC" has been used to FoRCe
rebuilding (since the target/dependency does not exist... unless someone
creates an "FRC" file).
BUGS
The make syntax is difficult to parse without actually acting on the
data. For instance, finding the end of a variable's use should involve
scanning each of the modifiers, using the correct terminator for each
field. In many places make just counts {} and () in order to find the
end of a variable expansion.
There is no way of escaping a space character in a filename.
FreeBSD 13.1-RELEASE-p6 January 28, 2022 FreeBSD 13.1-RELEASE-p6
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