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MAKE(1) 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 option is given, make tries 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 (from 1993).
make prepends 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 making 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 are
passed on to 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, the standard output is
line buffered. The available flags are:
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 the 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 `+', the file is opened in append mode; otherwise the
file is overwritten. If the file name is `stdout' or
`stderr', debugging output is written to the standard
output or standard error output file descriptors
respectively (and the `+' option has no effect).
Otherwise, the output is written to the named file. If
the file name ends with `.%d', 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 throws 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 and
expansion.
x Run shell commands with -x so the actual commands are
printed as they are executed.
-e Let environment variables override global variables within
makefiles.
-f makefile
Specify a makefile to read instead of the default makefile or
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 option 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
overrides the default system include path /usr/share/mk.
Furthermore, the system include path is appended to the search
path used for "file"-style include statements (see the -I
option).
If a directory name in the -m argument (or the MAKESYSPATH
environment variable) starts with the string `.../', make
searches for the specified file or directory named in the
remaining part of the argument string. The search starts with
the current directory and then works upward towards the root of
the file system. If the search is successful, the resulting
directory replaces the `.../' specification in the -m argument.
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 that 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, instead 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 are
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 `$', the
value is recursively expanded to its complete resultant text
before printing. The expanded value is also 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 all printed variables are always expanded to their
complete value. The last occurrence of -V or -v decides whether
all variables are expanded or not.
-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 several different types of lines in a makefile: dependency
specifications, shell commands, variable assignments, include statements,
conditional directives, for loops, other directives, and comments.
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 is 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
is not 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 only match 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 occur 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 is
passed to the shell; otherwise make attempts direct execution. If a line
starts with `-' and the shell has ErrCtl enabled, failure of the command
line is ignored as in compatibility mode. Otherwise `-' affects the
entire job; the script stops at the first command line that fails, but
the target is not 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 uses "cd" or
"chdir" without the intention of changing the directory for subsequent
commands should be put in parentheses so it executes in a subshell. To
force the use of a single 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 changes the current working directory to `.OBJDIR' before
executing any targets, each child process starts with that as its current
working directory.
VARIABLE ASSIGNMENTS
Variables in make behave much like macros in the C preprocessor.
Variable assignments have the form `NAME op value', where:
NAME is a single-word variable name, consisting, by tradition, of all
upper-case letters,
op is one of the five variable assignment operators described below,
and
value is interpreted according to the variable assignment operator.
Whitespace around NAME, op and value is discarded.
Variable assignment operators
The five operators that assign values to variables are:
= Assign the value to the variable. Any previous value is
overwritten.
+= Append the value to the current value of the variable, separating
them by a single space.
?= 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, then
assign the output from the child's standard output to the
variable. Any newlines in the result are replaced with spaces.
Expansion of variables
In most contexts where variables are expanded, `$$' expands to a single
dollar sign. In other contexts (most variable modifiers, string literals
in conditions), `\$' expands to a single dollar sign.
References to variables have the form ${name[:modifiers]} or
$(name[:modifiers]). If the variable name consists of only a single
character, the surrounding curly braces or parentheses are not required.
This shorter form is not recommended.
If the variable name contains a dollar, 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 nested variable expression contains a dollar
sign (`$'), the string is subject to further expansion.
Variable substitution occurs at four 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 conditionals are expanded individually, but only as far
as necessary to determine the result of the conditional.
3. Variables in shell commands are expanded when the shell command is
executed.
4. .for loop index variables are expanded on each loop iteration. Note
that other variables are not expanded when composing the body of a
loop, so the following example code:
.for i in 1 2 3
a+= ${i}
j= ${i}
b+= ${j}
.endfor
all:
@echo ${a}
@echo ${b}
prints:
1 2 3
3 3 3
Because while a contains `${:U1} ${:U2} ${:U3}' after the loop is
executed, b contains `${j} ${j} ${j}' which expands to `3 3 3' since
after the loop completes j contains `${:U3}'.
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, unless
.MAKE.TARGET_LOCAL_VARIABLES is set to `false'. The rest of the line
(which already has 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}' are impacted by that filter (in "meta" mode)
and simply enabling/disabling any of the compiler wrappers does 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:
.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 is not 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:
.ALLTARGETS The list of all targets encountered in the makefiles. 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 make
variants and cannot be confused with the special target
with the same name.
.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, the 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, setting .MAKE.JOB.PREFIX to
`${.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 added to the
environment for all programs that make executes.
.MAKE.LEVEL The recursion depth of make. The top-level instance of
make has level 0, and each child make has its parent
level plus 1. This allows tests like: .if ${.MAKE.LEVEL}
== 0 to protect things which should only be evaluated in
the top-level instance of make.
.MAKE.MAKEFILE_PREFERENCE
The ordered list of makefile names (default `makefile',
`Makefile') that make looks 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. Affects 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 useful
when diagnosing errors.
curdirOk=bf By default, make does 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, a missing .meta file
makes the target out-of-date.
missing-filemon=bf If bf is true, 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 is the expanded 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.
randomize-targets In both compat and parallel mode, do
not make the targets in the usual
order, but instead randomize their
order. This mode can be used to
detect undeclared dependencies
between files.
.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 are 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
If true, `$$' are preserved when doing `:=' assignments.
The default is true, for compatibility with other makes.
If set to false, `$$' becomes `$' per normal evaluation
rules.
.MAKE.UID The numeric ID of the user running make.
.MAKE.GID The numeric group ID of the user 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, in case of an error, make
prints the variable names and their values using:
${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 is
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 changes to the
specified directory if it exists, and sets `.OBJDIR' and
`PWD' to that directory before executing any targets.
Except in the case of an explicit `.OBJDIR' target, make
checks that the specified directory is writable and
ignores it if not. This check can be skipped by setting
the environment variable `MAKE_OBJDIR_CHECK_WRITABLE' to
"no".
.PARSEDIR The directory name 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. To retain their current
values, assign them to a variable using assignment with
expansion `:='.
.PATH The space-separated list of directories that make
searches for files. To update this search list, use the
special target `.PATH' rather than modifying the variable
directly.
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, 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 The colon-separated (":") list of directories that make
searches for files. This variable is supported for
compatibility with old make programs only, use `.PATH'
instead.
Variable modifiers
The general format of a variable expansion is:
${variable[:modifier[:...]]}
Each modifier begins with a colon. To escape a colon, precede it with a
backslash `\'.
A list of indirect 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 colon already occurs in the referencing
variable. If any of the modifiers in the modifier_variable contains a
dollar sign (`$'), these must be doubled to avoid early expansion.
Some modifiers interpret the expression value as a single string, others
treat the expression value as a whitespace-separated list of words. When
splitting a string into words, whitespace can be escaped using double
quotes, single quotes and backslashes, like in the shell. The quotes and
backslashes are retained in the words.
The supported modifiers are:
:E Replaces each word in the variable with its suffix.
:H Replaces each word in the variable with its dirname.
: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,
the construct
${VAR:M*}
removes all leading and trailing whitespace and normalizes the
inter-word spacing to a single space.
:Npattern
This is the opposite of `:M', selecting all words which do not match
pattern.
:O Orders the words alphabetically.
:On Orders the words numerically. A number followed by one of `k', `M'
or `G' is multiplied by the appropriate factor, which is 1024 for
`k', 1048576 for `M', or 1073741824 for `G'. Both upper- and lower-
case letters are accepted.
:Or Orders the words in reverse alphabetical order.
:Orn
Orders the words in reverse numerical order.
:Ox Shuffles the words. The results are 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 value, so that it can be
passed safely to the shell.
:q Quotes every shell meta-character in the value, 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[=timestamp]
The value is interpreted as a format string for strftime(3), using
gmtime(3), producing the formatted timestamp. If a timestamp value
is not provided or is 0, the current time is used.
:hash
Computes a 32-bit hash of the value and encodes it as 8 hex digits.
:localtime[=timestamp]
The value is interpreted as a format string for strftime(3), using
localtime(3), producing the formatted timestamp. If a timestamp
value is not provided or is 0, the current time is used.
:tA Attempts to convert the value to an absolute path using realpath(3).
If that fails, the value is unchanged.
:tl Converts the value to lower-case letters.
:tsc
When joining the words after a modifier that treats the value as
words, the words are normally separated by a space. This modifier
changes the separator to the character c. If c is omitted, no
separator is used. The common escapes (including octal numeric
codes) work as expected.
:tu Converts the value to upper-case letters.
:tW Causes subsequent modifiers to treat the value as a single word
(possibly containing embedded whitespace). See also `:[*]'.
:tw Causes the value to be treated as a list of words. See also `:[@]'.
:S/old_string/new_string/[1gW]
Modifies the first occurrence of old_string in each word of the
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, the value is treated
as a single word. 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 the anchoring `^' or `$'). Any character may be
used as the delimiter for the parts of the modifier string. The
anchoring, ampersand and delimiter characters can 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 works like the :S modifier except that the old and
new strings, instead of being simple strings, are an extended
regular expression pattern (see regex(3)) and an ed(1)-style
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 whitespace).
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
(basename).
: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, of course, usually contains
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 `%', 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, the result
is the new_string. If only the new_string contains the pattern
matching character `%', 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.
:@varname@string@
This is the loop expansion mechanism from the OSF Development
Environment (ODE) make. Unlike .for loops, expansion occurs at the
time of reference. For each word in the value, assign the word to
the variable named varname and evaluate string. The ODE convention
is that varname should start and end with a period, for example:
${LINKS:@.LINK.@${LN} ${TARGET} ${.LINK.}@}
However, a single-letter 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, the name of the
variable is used. In order for this modifier to work, the name
(node) must at least have appeared on the right-hand side of a
dependency.
:!cmd!
The output of running cmd is the value.
:sh The value 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 at a point where a target's shell commands
are being parsed. These assignment modifiers always expand to
nothing.
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 split into
words.
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, 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, 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 whitespace). 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 whitespace. Analogous to the effect of
$@ in Bourne shell.
# Returns the number of words in the value.
DIRECTIVES
Makefile inclusion, conditional structures and for loops are provided in
make. All such structures are identified by a line beginning with a
single dot (`.') character, followed by the keyword of the directive,
such as include or if.
File inclusion
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 make variants, `include file ...' (without
leading dot) is also accepted.
If the include statement is written as .-include or as .sinclude, 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 are ignored just like in .MAKE.DEPENDFILE.
Exporting variables
The directives for exporting and unexporting variables are:
.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 (without leading dot)
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.
.unexport variable ...
The opposite of `.export'. The specified global variable is
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 causes 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' is also
pushed into the new environment.
Messages
The directives for printing messages to the output are:
.info message
The message is printed along with the name of the makefile and
line number.
.warning message
The message prefixed by `warning:' is printed along with the name
of the makefile and line number.
.error message
The message is printed along with the name of the makefile and
line number, make exits immediately.
Conditionals
The directives for conditionals are:
.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 requested.
.ifnmake [!]target [operator target ...]
Test the target being requested.
.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 `||'.
make only evaluates a conditional as far as is necessary to determine its
value. Parentheses can be used to override the operator precedence. 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 name, with possible modifiers, and evaluates to
true if the expansion of the variable results 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. If both sides
are numeric and neither is enclosed in quotes, the comparison is done
numerically, otherwise lexicographically. A string is interpreted as
hexadecimal integer if it is preceded by 0x, otherwise it is a decimal
floating-point number; octal numbers are not supported.
All comparisons may use the operators `==' and `!='. Numeric comparisons
may also use the operators `<', `<=', `>' and `>='.
If the comparison has neither a comparison operator nor a right side, the
expression evaluates to true if it is nonempty and its numeric value (if
any) is not zero.
When make is evaluating one of these conditional expressions, and it
encounters a (whitespace separated) word it doesn't recognize, either the
"make" or "defined" function is applied to it, depending on the form of
the conditional. If the form is `.ifdef', `.ifndef' or `.if', the
"defined" function is applied. Similarly, if the form is `.ifmake' or
`.ifnmake', the "make" function is applied.
If the conditional evaluates to true, parsing of the makefile continues
as before. If it evaluates to false, the following lines are skipped.
In both cases, this continues until the corresponding `.else' or `.endif'
is found.
For loops
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
The expression is expanded and then 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.
If `.break' is encountered within a .for loop, it causes early
termination of the loop, otherwise a parse error.
Other directives
.undef variable ...
Un-define the specified global variables. Only global variables
can be un-defined.
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 is still considered 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 is compared
@echo this is not ${.OODATE:M.NOMETA_CMP}
@echo this is also 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 ignores this fact and assumes 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 is not 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
Like .USE, but instead of appending, 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 successfully.
.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 are
executed.
.MAIN If no target is specified when make is invoked, this target is
built.
.MAKEFLAGS
This target provides a way to specify flags for make at the time
when the makefiles are read. The flags are as if typed to the
shell, though the -f option has 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
changes the current working directory to it and updates the
value of `.OBJDIR'.
.ORDER In parallel mode, 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
.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 removed from
the search path. If the source is the special .DOTLAST target,
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.
.POSIX If this is the first non-comment line in the main makefile, the
variable %POSIX is set to the value `1003.2' and the makefile
`<posix.mk>' is included if it exists, to provide POSIX-
compatible default rules. If make is run with the -r flag, only
`posix.mk' contributes to the default rules.
.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 uses 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 absolute 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 make variants;
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)
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.
NetBSD 9.99 September 12, 2022 NetBSD 9.99