xref: /freebsd/contrib/bmake/bmake.cat1 (revision 5956d97f4b3204318ceb6aa9c77bd0bc6ea87a41)

BMAKE(1)                FreeBSD General Commands Manual               BMAKE(1)

NAME
     bmake — maintain program dependencies

SYNOPSIS
     bmake [-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
     bmake is a program designed to simplify the maintenance of other pro‐
     grams.  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, bmake 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 bmake and makefiles, please refer to PMake - A
     Tutorial.

     bmake 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 any‐
             thing else.  If multiple -C options are specified, each is inter‐
             preted 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 bmake 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 un‐
             buffered; in addition, if debugging is enabled but debugging out‐
             put 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 direc‐
                     tory.

             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, includ‐
                     ing 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 vari‐
                     able, 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 mainte‐
                     nance.

             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.  Equiva‐
             lent 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 bmake may have running at
             any one time.  The value is saved in .MAKE.JOBS.  Turns compati‐
             bility 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 tra‐
             ditional one shell invocation per line.  This can break tradi‐
             tional scripts which change directories on each command invoca‐
             tion 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.  Fur‐
             thermore the system include path will be appended to the search
             path used for "file"-style include statements (see the -I op‐
             tion).

             If a file or directory name in the -m argument (or the
             MAKESYSPATH environment variable) starts with the string ".../"
             then bmake 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 success‐
             ful, then the resulting directory replaces the ".../" specifica‐
             tion in the -m argument.  If used, this feature allows bmake 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 spe‐
             cial 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 unde‐
             fined 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 vari‐
             able 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 vari‐
             ables during makefile processing, are not accessible via this op‐
             tion.  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 pro‐
             cessing.

     -X      Don't export variables passed on the command line to the environ‐
             ment individually.  Variables passed on the command line are
             still exported via the MAKEFLAGS environment variable.  This op‐
             tion 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.  Vari‐
             able 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 consid‐
     ered 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 bmake is inter‐
           rupted, 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 at‐
           tached shell commands are run if the target is out of date with re‐
           spect to (only) those sources.  Thus, different groups of the at‐
           tached 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 bmake is interrupted.
     All dependency lines mentioning a particular target must use the same op‐
     erator.

     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 ex‐
     isting 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 com‐
     mands, 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 de‐
     sired, 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 sin‐
     gle line of a script.  A ‘-’ in compatibility mode causes any non-zero
     exit status of the command line to be ignored.

     When bmake 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 com‐
     mand contains any shell meta characters (‘#=|^(){};&<>*?[]:$`\\n’) it
     will be passed to the shell; otherwise bmake will attempt direct execu‐
     tion.  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 bmake operation does not
     change their behavior.  For example, any command which needs to use “cd”
     or “chdir” without potentially changing the directory for subsequent com‐
     mands 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 bmake 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 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 can be used to assign values to variables are:

     =       Assign the value to the variable.  Any previous value is over‐
             written.

     +=      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 vari‐
             able 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 as‐
             sign the result to the variable.  Any newlines in the result are
             replaced with spaces.

   Expansion of variables
     In contexts where variables are expanded, ‘$$’ expands to a single dollar
     sign.  References to variables have the form ‘${name[:modifiers]}’ or
     ‘$(name[:modifiers]’).  If the variable name contains only a single char‐
     acter, the surrounding curly 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 con‐
     taining 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 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}

          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 prece‐
     dence) are:

     Environment variables
             Variables defined as part of bmake'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 compiler 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 recog‐
                     nized.

           .TARGET   The name of the target; also known as ‘@’.  For compati‐
                     bility 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, bmake sets or knows about the following variables:

     .ALLTARGETS     The list of all targets encountered in the Makefile.  If
                     evaluated during Makefile parsing, lists only those tar‐
                     gets encountered thus far.

     .CURDIR         A path to the directory where bmake 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 bmake was executed with (argv[0]).  For
                     compatibility bmake 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
                     bmake and cannot be confused with the special target with
                     the same name.

     .MAKE.DEPENDFILE
                     Names the makefile (default ‘.depend’) from which gener‐
                     ated 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 refer‐
                     ences) are shown.

     .MAKE.EXPORTED  The list of variables exported by bmake.

     .MAKE.JOBS      The argument to the -j option.

     .MAKE.JOB.PREFIX
                     If bmake 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 ex‐
                     ample, setting .MAKE.JOB.PREFIX to
                     ${.newline}---${.MAKE:T}[${.MAKE.PID}] would produce to‐
                     kens 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 de‐
                     pendency lines are treated as normal sources.

     MAKEFLAGS       The environment variable ‘MAKEFLAGS’ may contain anything
                     that may be specified on bmake's command line.  Anything
                     specified on bmake's command line is appended to the
                     ‘MAKEFLAGS’ variable which is then entered into the envi‐
                     ronment for all programs which bmake executes.

     .MAKE.LEVEL     The recursion depth of bmake.  The initial instance of
                     bmake will be 0, and an incremented value is put into the
                     environment to be seen by the next generation.  This al‐
                     lows tests like: .if ${.MAKE.LEVEL} == 0 to protect
                     things which should only be evaluated in the initial in‐
                     stance of bmake.

     .MAKE.MAKEFILE_PREFERENCE
                     The ordered list of makefile names (default ‘makefile’,
                     ‘Makefile’) that bmake will look for.

     .MAKE.MAKEFILES
                     The list of makefiles read by bmake, 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 bmake runs in.  It can contain a number of key‐
                     words:

                     compat               Like -B, puts bmake into "compat"
                                          mode.

                     meta                 Puts bmake into "meta" mode, where
                                          meta files are created for each tar‐
                                          get to capture the command run, the
                                          output generated and if filemon(4)
                                          is available, the system calls which
                                          are of interest to bmake.  The cap‐
                                          tured output can be very useful when
                                          diagnosing errors.

                     curdirOk= bf         Normally bmake 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 deter‐
                                          mining 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 de‐
                                          tect undeclared dependencies between
                                          files.

     .MAKE.META.BAILIWICK
                     In "meta" mode, provides a list of prefixes which match
                     the directories controlled by bmake.  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 fil‐
                     tered 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 informa‐
                     tion.

     .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 ex‐
                     ported as part of ‘MAKEFLAGS’.  This behavior can be dis‐
                     abled 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 bmake 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 bmake.

     .MAKE.PPID      The parent process-id of bmake.

     .MAKE.SAVE_DOLLARS
                     value should be a boolean that controls whether ‘$$’ are
                     preserved when doing ‘:=’ assignments.  The default is
                     false, for backwards compatibility.  Set to true for com‐
                     patability with other makes.  If set to false, ‘$$’ be‐
                     comes ‘$’ per normal evaluation rules.

     .MAKE.UID       The user-id running bmake.

     .MAKE.GID       The group-id running bmake.

     MAKE_PRINT_VAR_ON_ERROR
                     When bmake 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 follow‐
                     ing directories in order and using the first match:

                     1.   ${MAKEOBJDIRPREFIX}${.CURDIR}

                          (Only if ‘MAKEOBJDIRPREFIX’ is set in the environ‐
                          ment 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, bmake 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, bmake
                     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 as‐
                     signment with expansion ‘:=’.

     .PATH           A variable that represents the list of directories that
                     bmake will search for files.  The search list should be
                     updated using the target ‘.PATH’ rather than the vari‐
                     able.

     PWD             Alternate path to the current directory.  bmake 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 bmake 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 bmake 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 bmake
                     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 charac‐
     ters).  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 com‐
          ponent.

     :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 in‐
          vocations of bmake.  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 orig‐
          inal 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 expan‐
          sion.  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 ap‐
          pended 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 ap‐
          pended 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 pre‐
          ceding 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 regu‐
          lar 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 condi‐
          tional 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 en‐
          tire words may be replaced.  Otherwise % is the substring of
          old_string to be replaced in new_string.  If only old_string con‐
          tains 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 pre‐
          ceding dollar sign as is usual.

     :@temp@string@
          This is the loop expansion mechanism from the OSF Development Envi‐
          ronment (ODE) make.  Unlike .for loops, expansion occurs at the time
          of reference.  Assigns temp to each word in the variable and evalu‐
          ates 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 in‐
          stance:
                ${_${.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 bmake 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 opera‐
          tions 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 inte‐
          gers (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 re‐
          sult 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 out‐
                 put in reverse order.  For example, ‘:[-1..1]’ selects all
                 the words from last to first.  If the list is already or‐
                 dered, 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 bmake.  All such structures
     are identified by a line beginning with a single dot (‘.’) character.
     Files are included with either .include <file> or .include "file".  Vari‐
     ables between the angle brackets or double quotes are expanded to form
     the file name.  If angle brackets are used, the included makefile is ex‐
     pected 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 bmake ‘include file ...’ is also
     accepted.

     If the include statement is written as .-include or as .sinclude then er‐
     rors locating and/or opening include files are ignored.

     If the include statement is written as .dinclude not only are errors lo‐
     cating 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 bmake 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 bmake programs ‘export variable=value’ is also accepted.

             Appending a variable name to .MAKE.EXPORTED is equivalent to ex‐
             porting 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 environ‐
             ment which is different from that used by bmake 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 environ‐
             ment inherited from the parent.  This operation will cause a mem‐
             ory leak of the original environment, so should be used spar‐
             ingly.  Testing for .MAKE.LEVEL being 0, would make sense.  Also
             note that any variables which originated in the parent environ‐
             ment 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, bmake 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 bmake's command line or was de‐
              clared 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 ex‐
     pansion is performed on both sides of the comparison, after which the nu‐
     merical values are compared.  A value is interpreted as hexadecimal if it
     is preceded by 0x, otherwise it is decimal; octal numbers are not sup‐
     ported.  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 bmake is evaluating one of these conditional expressions, and it en‐
     counters 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 contin‐
     ues 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 com‐
     mand 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 any‐
               way.

     .IGNORE   Ignore any errors from the commands associated with this tar‐
               get, 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
               bmakes.

     .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 de‐
               sired:


                     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 vari‐
               able.

     .NOPATH   Do not search for the target in the directories specified by
               .PATH.

     .NOTMAIN  Normally bmake 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 bmake can't fig‐
               ure 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 bmake is interrupted, it normally removes any partially
               made targets.  This source prevents the target from being re‐
               moved.

     .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 bmake's version of a macro.  When the tar‐
               get 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 it‐
               self 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 bmake can't figure out any other way to cre‐
              ate.  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 be‐
              ing left around and corrupting future rebuilds.

     .END     Any command lines attached to this target are executed after ev‐
              erything else is done.

     .ERROR   Any command lines attached to this target are executed when an‐
              other 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 bmake is interrupted, the commands for this target will be
              executed.

     .MAIN    If no target is specified when bmake is invoked, this target
              will be built.

     .MAKEFLAGS
              This target provides a way to specify flags for bmake 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, bmake
              will chdir(2) to it and update 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 tar‐
              get 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 speci‐
              fied, 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.

     .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-compati‐
              ble default rules.  If bmake is run with the -r flag, then only
              ‘posix.mk’ will contribute to the default rules.

     .PRECIOUS
              Apply the .PRECIOUS attribute to any specified sources.  If no
              sources are specified, the .PRECIOUS attribute is applied to ev‐
              ery target in the file.

     .SHELL   Sets the shell that bmake 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 exe‐
                          cuted.

              filter      The output to filter after issuing the quiet com‐
                          mand.  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 echo‐
                          ing.

              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 en‐
              tries, having .ALLSRC set to the name of that dependency file.

     .SUFFIXES
              Each source specifies a suffix to bmake.  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
     bmake 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 bmake and not as makefile variables; see the descrip‐
     tion 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 bmake:

     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 us‐
     ing 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 algo‐
     rithms used may change again in the future.

   Other make dialects
     Other make dialects (GNU make, SVR4 make, POSIX make, etc.) do not sup‐
     port most of the features of bmake as described in this manual.  Most no‐
     tably:

           •   The .WAIT and .ORDER declarations and most functionality per‐
               taining 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 be‐
     havior 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 cur‐
     rent directory, not trying to chain transformations together, etc.) is
     also reasonably portable.

SEE ALSO
     mkdep(1)

HISTORY
     bmake is derived from NetBSD make(1).  It uses autoconf to facilitate
     portability to other platforms.

     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 rebuild‐
     ing (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 13.0                     July 12, 2022                    FreeBSD 13.0