Provided by: bmake_20160220-2build1_amd64 bug

NAME

     bmake — maintain program dependencies

SYNOPSIS

     bmake [-BeikNnqrstWwX] [-C directory] [-D variable] [-d flags] [-f makefile] [-I directory]
           [-J private] [-j max_jobs] [-m directory] [-T file] [-V variable] [variable=value]
           [target ...]

DESCRIPTION

     bmake is a program designed to simplify the maintenance of other programs.  Its input is a
     list of specifications as to the files upon which programs and other files depend.  If no -f
     makefile makefile option is given, 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 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 context.

     -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 unbuffered; in addition, if
             debugging is enabled but debugging output is not directed to standard output, then
             the standard output is line buffered.  Flags is one or more of the following:

             A       Print all possible debugging information; equivalent to specifying all of
                     the debugging flags.

             a       Print debugging information about archive searching and caching.

             C       Print debugging information about current working directory.

             c       Print debugging information about conditional evaluation.

             d       Print debugging information about directory searching and caching.

             e       Print debugging information about failed commands and targets.

             F[+]filename
                     Specify where debugging output is written.  This must be the last flag,
                     because it consumes the remainder of the argument.  If the character
                     immediately after the ‘F’ flag is ‘+’, then the file will be opened in
                     append mode; otherwise the file will be overwritten.  If the file name is
                     ‘stdout’ or ‘stderr’ then debugging output will be written to the standard
                     output or standard error output file descriptors respectively (and the ‘+’
                     option has no effect).  Otherwise, the output will be written to the named
                     file.  If the file name ends ‘.%d’ then the ‘%d’ is replaced by the pid.

             f       Print debugging information about loop evaluation.

             g1      Print the input graph before making anything.

             g2      Print the input graph after making everything, or before exiting on error.

             g3      Print the input graph before exiting on error.

             j       Print debugging information about running multiple shells.

             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.

             v       Print debugging information about variable assignment.

             x       Run shell commands with -x so the actual commands are printed as they are
                     executed.

     -e      Specify that environment variables override macro assignments within makefiles.

     -f makefile
             Specify a makefile to read instead of the default ‘makefile’.  If makefile is ‘-’,
             standard input is read.  Multiple makefiles may be specified, and are read in the
             order specified.

     -I directory
             Specify a directory in which to search for makefiles and included makefiles.  The
             system makefile directory (or directories, see the -m option) is automatically
             included as part of this list.

     -i      Ignore non-zero exit of shell commands in the makefile.  Equivalent to specifying
             ‘-’ before each command line in the makefile.

     -J private
             This option should not be specified by the user.

             When the j option is in use in a recursive build, this option is passed by a make to
             child makes to allow all the make processes in the build to cooperate to avoid
             overloading the system.

     -j max_jobs
             Specify the maximum number of jobs that bmake may have running at any one time.  The
             value is saved in .MAKE.JOBS.  Turns compatibility mode off, unless the B flag is
             also specified.  When compatibility mode is off, all commands associated with a
             target are executed in a single shell invocation as opposed to the traditional one
             shell invocation per line.  This can break traditional scripts which change
             directories on each command invocation and then expect to start with a fresh
             environment on the next line.  It is more efficient to correct the scripts rather
             than turn backwards compatibility on.

     -k      Continue processing after errors are encountered, but only on those targets that do
             not depend on the target whose creation caused the error.

     -m directory
             Specify a directory in which to search for sys.mk and makefiles included via the
             ⟨file⟩-style include statement.  The -m option can be used multiple times to form a
             search path.  This path will override the default system include path:
             /usr/share/mk.  Furthermore the system include path will be appended to the search
             path used for "file"-style include statements (see the -I option).

             If a file or directory name in the -m argument (or the MAKESYSPATH environment
             variable) starts with the string ".../" then 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 filesystem.  If the search is successful, then the resulting directory
             replaces the ".../" specification 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 special source (see below).

     -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      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 bmake's idea of the value of variable, in the global context.  Do not build
             any targets.  Multiple instances of this option may be specified; the variables will
             be printed one per line, with a blank line for each null or undefined variable.  If
             variable contains a ‘$’ then the value will be expanded before printing.

     -W      Treat any warnings during makefile parsing as errors.

     -w      Print entering and leaving directory messages, pre and post processing.

     -X      Don't export variables passed on the command line to the environment individually.
             Variables passed on the command line are still exported via the MAKEFLAGS
             environment variable.  This option may be useful on systems which have a small limit
             on the size of command arguments.

     variable=value
             Set the value of the variable variable to value.  Normally, all values passed on the
             command line are also exported to sub-makes in the environment.  The -X flag
             disables this behavior.  Variable assignments should follow options for POSIX
             compatibility but no ordering is enforced.

     There are seven different types of lines in a makefile: file dependency specifications,
     shell commands, variable assignments, include statements, conditional directives, for loops,
     and comments.

     In general, lines may be continued from one line to the next by ending them with a backslash
     (‘\’).  The trailing newline character and initial whitespace on the following line are
     compressed into a single space.

FILE DEPENDENCY SPECIFICATIONS

     Dependency lines consist of one or more targets, an operator, and zero or more sources.
     This creates a relationship where the targets “depend” on the sources and are usually
     created from them.  The exact relationship between the target and the source is determined
     by the operator that separates them.  The three operators are as follows:

     :     A target is considered out-of-date if its modification time is less than those of any
           of its sources.  Sources for a target accumulate over dependency lines when this
           operator is used.  The target is removed if bmake is interrupted.

     !     Targets are always re-created, but not until all sources have been examined and re-
           created as necessary.  Sources for a target accumulate over dependency lines when this
           operator is used.  The target is removed if bmake is interrupted.

     ::    If no sources are specified, the target is always re-created.  Otherwise, a target is
           considered out-of-date if any of its sources has been modified more recently than the
           target.  Sources for a target do not accumulate over dependency lines when this
           operator is used.  The target will not be removed if bmake is interrupted.

     Targets and sources may contain the shell wildcard values ‘?’, ‘*’, ‘[]’, and ‘{}’.  The
     values ‘?’, ‘*’, and ‘[]’ may only be used as part of the final component of the target or
     source, and must be used to describe existing files.  The value ‘{}’ need not necessarily be
     used to describe existing files.  Expansion is in directory order, not alphabetically as
     done in the shell.

SHELL COMMANDS

     Each target may have associated with it one or more lines of shell commands, normally used
     to create the target.  Each of the lines in this script must be preceded by a tab.  (For
     historical reasons, spaces are not accepted.)  While targets can appear in many dependency
     lines if desired, by default only one of these rules may be followed by a creation script.
     If the ‘::’ operator is used, however, all rules may include scripts and the scripts are
     executed in the order found.

     Each line is treated as a separate shell command, unless the end of line is escaped with a
     backslash (‘\’) in which case that line and the next are combined.  If the first characters
     of the command are any combination of ‘@’, ‘+’, or ‘-’, the command is treated specially.  A
     ‘@’ causes the command not to be echoed before it is executed.  A ‘+’ causes the command to
     be executed even when -n is given.  This is similar to the effect of the .MAKE special
     source, except that the effect can be limited to a single line of a script.  A ‘-’ in
     compatibility mode causes any non-zero exit status of the command line to be ignored.

     When 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 command contains any shell meta characters
     (‘#=|^(){};&<>*?[]:$`\\n’) it will be passed to the shell; otherwise bmake will attempt
     direct execution.  If a line starts with ‘-’ and the shell has ErrCtl enabled then failure
     of the command line will be ignored as in compatibility mode.  Otherwise ‘-’ affects the
     entire job; the script will stop at the first command line that fails, but the target will
     not be deemed to have failed.

     Makefiles should be written so that the mode of 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 commands should be put in parentheses so it executes
     in a subshell.  To force the use of one shell, escape the line breaks so as to make the
     whole script one command.  For example:

           avoid-chdir-side-effects:
                   @echo Building $@ in `pwd`
                   @(cd ${.CURDIR} && ${MAKE} $@)
                   @echo Back in `pwd`

           ensure-one-shell-regardless-of-mode:
                   @echo Building $@ in `pwd`; \
                   (cd ${.CURDIR} && ${MAKE} $@); \
                   echo Back in `pwd`

     Since 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 are much like variables in the shell, and, by tradition, consist of all
     upper-case letters.

   Variable assignment modifiers
     The five operators that can be used to assign values to variables are as follows:

     =       Assign the value to the variable.  Any previous value is overridden.

     +=      Append the value to the current value of the variable.

     ?=      Assign the value to the variable if it is not already defined.

     :=      Assign with expansion, i.e. expand the value before assigning it to the variable.
             Normally, expansion is not done until the variable is referenced.  NOTE: References
             to undefined variables are not expanded.  This can cause problems when variable
             modifiers are used.

     !=      Expand the value and pass it to the shell for execution and assign the result to the
             variable.  Any newlines in the result are replaced with spaces.

     Any white-space before the assigned value is removed; if the value is being appended, a
     single space is inserted between the previous contents of the variable and the appended
     value.

     Variables are expanded by surrounding the variable name with either curly braces (‘{}’) or
     parentheses (‘()’) and preceding it with a dollar sign (‘$’).  If the variable name contains
     only a single letter, the surrounding braces or parentheses are not required.  This shorter
     form is not recommended.

     If the variable name contains a dollar, then the name itself is expanded first.  This allows
     almost arbitrary variable names, however names containing dollar, braces, parenthesis, or
     whitespace are really best avoided!

     If the result of expanding a variable contains a dollar sign (‘$’) the string is expanded
     again.

     Variable substitution occurs at three distinct times, depending on where the variable is
     being used.

     1.   Variables in dependency lines are expanded as the line is read.

     2.   Variables in shell commands are expanded when the shell command is executed.

     3.   “.for” loop index variables are expanded on each loop iteration.  Note that other
          variables are not expanded inside loops so the following example code:

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

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

          will print:

                1 2 3
                3 3 3

          Because while ${a} contains “1 2 3” after the loop is executed, ${b} contains “${j}
          ${j} ${j}” which expands to “3 3 3” since after the loop completes ${j} contains “3”.

   Variable classes
     The four different classes of variables (in order of increasing precedence) are:

     Environment variables
             Variables defined as part of 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 are all built in and their values vary magically from target to target.  It
     is not currently possible to define new local variables.  The seven local variables are as
     follows:

           .ALLSRC   The list of all sources for this target; also known as ‘>’.

           .ARCHIVE  The name of the archive file; also known as ‘!’.

           .IMPSRC   In suffix-transformation rules, the name/path of the source from which the
                     target is to be transformed (the “implied” source); also known as ‘<’.  It
                     is not defined in explicit rules.

           .MEMBER   The name of the archive member; also known as ‘%’.

           .OODATE   The list of sources for this target that were deemed out-of-date; also known
                     as ‘?’.

           .PREFIX   The file prefix of the target, containing only the file portion, no suffix
                     or preceding directory components; also known as ‘*’.  The suffix must be
                     one of the known suffixes declared with .SUFFIXES or it will not be
                     recognized.

           .TARGET   The name of the target; also known as ‘@’.

     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:

     $               A single dollar sign ‘$’, i.e.  ‘$$’ expands to a single dollar sign.

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

     .CURDIR         A path to the directory where 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 generated dependencies are
                     read.

     .MAKE.EXPAND_VARIABLES
                     A boolean that controls the default behavior of the -V option.

     .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 then output for each target is prefixed with a token
                     ‘--- target ---’ the first part of which can be controlled via
                     .MAKE.JOB.PREFIX.  If .MAKE.JOB.PREFIX is empty, no token is printed.
                     For example: .MAKE.JOB.PREFIX=${.newline}---${.MAKE:T}[${.MAKE.PID}] would
                     produce tokens like ‘---make[1234] target ---’ making it easier to track the
                     degree of parallelism being achieved.

     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
                     environment 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 allows tests like: .if ${.MAKE.LEVEL} == 0 to protect
                     things which should only be evaluated in the initial instance 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 keywords:

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

                     meta        Puts bmake 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 bmake.  The captured 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.

                     env         For debugging, it can be useful to inlcude the environment in
                                 the .meta file.

                     verbose     If in "meta" mode, print a clue about the target being built.
                                 This is useful if the build is otherwise running silently.  The
                                 message printed the value of: .MAKE.META.PREFIX.

                     ignore-cmd  Some makefiles have commands which are simply not stable.  This
                                 keyword causes them to be ignored for determining whether a
                                 target is out of date in "meta" mode.  See also .NOMETA_CMP.

                     silent= bf  If bf is True, when a .meta file is created, mark the target
                                 .SILENT.

     .MAKE.META.BAILIWICK
                     In "meta" mode, provides a list of prefixes which match the directories
                     controlled by 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.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.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
                     behaviour 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 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 boolen that controls wether ‘$$’ are preserved when doing
                     ‘:=’ assignments.  The default is false, for backwards compatability.  Set
                     to true for compatability with other makes.  If set to false, ‘$$’ becomes
                     ‘$’ per normal evaluation rules.

     MAKE_PRINT_VAR_ON_ERROR
                     When bmake stops due to an error, it prints its name and the value of
                     ‘.CURDIR’ as well as the value of any variables named in
                     ‘MAKE_PRINT_VAR_ON_ERROR’.

     .newline        This variable is simply assigned a newline character as its value.  This
                     allows expansions using the :@ modifier to put a newline between iterations
                     of the loop rather than a space.  For example, the printing of
                     ‘MAKE_PRINT_VAR_ON_ERROR’ could be done as
                     ${MAKE_PRINT_VAR_ON_ERROR:@v@$v='${$v}'${.newline}@}.

     .OBJDIR         A path to the directory where the targets are built.  Its value is
                     determined by trying to chdir(2) to the following directories in order and
                     using the first match:

                     1.   ${MAKEOBJDIRPREFIX}${.CURDIR}

                          (Only if ‘MAKEOBJDIRPREFIX’ is set in the environment or on the command
                          line.)

                     2.   ${MAKEOBJDIR}

                          (Only if ‘MAKEOBJDIR’ is set in the environment or on the command
                          line.)

                     3.   ${.CURDIR}/obj.${MACHINE}

                     4.   ${.CURDIR}/obj

                     5.   /usr/obj/${.CURDIR}

                     6.   ${.CURDIR}

                     Variable expansion is performed on the value before it's used, so
                     expressions such as
                           ${.CURDIR:S,^/usr/src,/var/obj,}
                     may be used.  This is especially useful with ‘MAKEOBJDIR’.

                     ‘.OBJDIR’ may be modified in the makefile via the special target ‘.OBJDIR’.
                     In all cases, bmake will chdir(2) to the specified directory if it exists,
                     and set ‘.OBJDIR’ and ‘PWD’ to that directory before executing any targets.

     .PARSEDIR       A path to the directory of the current ‘Makefile’ being parsed.

     .PARSEFILE      The basename of the current ‘Makefile’ being parsed.  This variable and
                     ‘.PARSEDIR’ are both set only while the ‘Makefiles’ are being parsed.  If
                     you want to retain their current values, assign them to a variable using
                     assignment with expansion: (‘:=’).

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

     PWD             Alternate path to the current directory.  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 behaviour 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.

     .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 characters).  The general format of a variable
     expansion is as follows:

           ${variable[:modifier[:...]]}

     Each modifier begins with a colon, which may be escaped with a backslash (‘\’).

     A set of modifiers can be specified via a variable, as follows:

           modifier_variable=modifier[:...]
           ${variable:${modifier_variable}[:...]}

     In this case the first modifier in the modifier_variable does not start with a colon, since
     that must appear in the referencing variable.  If any of the modifiers in the
     modifier_variable contain a dollar sign (‘$’), these must be doubled to avoid early
     expansion.

     The supported modifiers are:

     :E   Replaces each word in the variable with its suffix.

     :H   Replaces each word in the variable with everything but the last component.

     :Mpattern
          Select 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 normalise 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   Order every word in variable alphabetically.  To sort words in reverse order use the
          ‘:O:[-1..1]’ combination of modifiers.

     :Ox  Randomize 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
          behaviour.  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
          through recursive invocations of bmake.

     :R   Replaces each word in the variable with everything but its suffix.

     :gmtime
          The value is a format string for strftime(3), using the current gmtime(3).

     :hash
          Compute a 32bit hash of the value and encode it as hex digits.

     :localtime
          The value is a format string for strftime(3), using the current localtime(3).

     :tA  Attempt to convert variable to an absolute path using realpath(3), if that fails, the
          value is unchanged.

     :tl  Converts variable to lower-case letters.

     :tsc
          Words in the variable are normally separated by a space on expansion.  This modifier
          sets the separator to the character c.  If c is omitted, then no separator is used.
          The common escapes (including octal numeric codes), work as expected.

     :tu  Converts variable to upper-case letters.

     :tW  Causes the value to be treated as a single word (possibly containing embedded white
          space).  See also ‘:[*]’.

     :tw  Causes the value to be treated as a sequence of words delimited by white space.  See
          also ‘:[@]’.

     :S/old_string/new_string/[1gW]
          Modify the first occurrence of old_string in the variable's value, replacing it with
          new_string.  If a ‘g’ is appended to the last slash of the pattern, all occurrences in
          each word are replaced.  If a ‘1’ is appended to the last slash of the pattern, only
          the first word is affected.  If a ‘W’ is appended to the last slash of the pattern,
          then the value is treated as a single word (possibly containing embedded white space).
          If old_string begins with a caret (‘^’), old_string is anchored at the beginning of
          each word.  If old_string ends with a dollar sign (‘$’), it is anchored at the end of
          each word.  Inside new_string, an ampersand (‘&’) is replaced by old_string (without
          any ‘^’ or ‘$’).  Any character may be used as a delimiter for the parts of the
          modifier string.  The anchoring, ampersand and delimiter characters may be escaped with
          a backslash (‘\’).

          Variable expansion occurs in the normal fashion inside both old_string and new_string
          with the single exception that a backslash is used to prevent the expansion of a dollar
          sign (‘$’), not a preceding dollar sign as is usual.

     :C/pattern/replacement/[1gW]
          The :C modifier is just like the :S modifier except that the old and new strings,
          instead of being simple strings, are an extended regular expression (see regex(3))
          string pattern and an ed(1)-style string replacement.  Normally, the first occurrence
          of the pattern pattern in each word of the value is substituted with replacement.  The
          ‘1’ modifier causes the substitution to apply to at most one word; the ‘g’ modifier
          causes the substitution to apply to as many instances of the search pattern pattern as
          occur in the word or words it is found in; the ‘W’ modifier causes the value to be
          treated as a single word (possibly containing embedded white space).  Note that ‘1’ and
          ‘g’ are orthogonal; the former specifies whether multiple words are potentially
          affected, the latter whether multiple substitutions can potentially occur within each
          affected word.

          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 component.

     :u   Remove adjacent duplicate words (like uniq(1)).

     :?true_string:false_string
          If the variable name (not its value), when parsed as a .if conditional expression,
          evaluates to true, return as its value the true_string, otherwise return the
          false_string.  Since the variable name is used as the expression, :? must be the first
          modifier after the variable name itself - which will, of course, usually contain
          variable expansions.  A common error is trying to use expressions like
                ${NUMBERS:M42:?match:no}
          which actually tests defined(NUMBERS), to determine is any words match "42" you need to
          use something like:
                ${"${NUMBERS:M42}" != "":?match:no}.

     :old_string=new_string
          This is the AT&T System V UNIX style variable substitution.  It must be the last
          modifier specified.  If old_string or new_string do not contain the pattern matching
          character % then it is assumed that they are anchored at the end of each word, so only
          suffixes or entire words may be replaced.  Otherwise % is the substring of old_string
          to be replaced in new_string.

          Variable expansion occurs in the normal fashion inside both old_string and new_string
          with the single exception that a backslash is used to prevent the expansion of a dollar
          sign (‘$’), not a preceding dollar sign as is usual.

     :@temp@string@
          This is the loop expansion mechanism from the OSF Development Environment (ODE) make.
          Unlike .for loops expansion occurs at the time of reference.  Assign temp to each word
          in the variable and evaluate 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}@}

     :Unewval
          If the variable is undefined newval is the value.  If the variable is defined, the
          existing value is returned.  This is another ODE make feature.  It is handy for setting
          per-target CFLAGS for instance:
                ${_${.TARGET:T}_CFLAGS:U${DEF_CFLAGS}}
          If a value is only required if the variable is undefined, use:
                ${VAR:D:Unewval}

     :Dnewval
          If the variable is defined newval is the value.

     :L   The name of the variable is the value.

     :P   The path of the node which has the same name as the variable is the value.  If no such
          node exists or its path is null, then the name of the variable is used.  In order for
          this modifier to work, the name (node) must at least have appeared on the rhs of a
          dependency.

     :!cmd!
          The output of running cmd is the value.

     :sh  If the variable is non-empty it is run as a command and the output becomes the new
          value.

     ::=str
          The variable is assigned the value str after substitution.  This modifier and its
          variations are useful in obscure situations such as wanting to set a variable when
          shell commands are being parsed.  These assignment modifiers always expand to nothing,
          so if appearing in a rule line by themselves should be preceded with something to keep
          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 operations related to the
          way in which the value is divided into words.

          Ordinarily, a value is treated as a sequence of words delimited by white space.  Some
          modifiers suppress this behaviour, causing a value to be treated as a single word
          (possibly containing embedded white space).  An empty value, or a value that consists
          entirely of white-space, is treated as a single word.  For the purposes of the ‘:[]’
          modifier, the words are indexed both forwards using positive integers (where index 1
          represents the first word), and backwards using negative integers (where index -1
          represents the last word).

          The range is subjected to variable expansion, and the expanded result is then
          interpreted as follows:

          index  Selects a single word from the value.

          start..end
                 Selects all words from start to end, inclusive.  For example, ‘:[2..-1]’ selects
                 all words from the second word to the last word.  If start is greater than end,
                 then the words are output in reverse order.  For example, ‘:[-1..1]’ selects all
                 the words from last to first.

          *      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 .includefile⟩ or .include
     "file".  Variables between the angle brackets or double quotes are expanded to form the file
     name.  If angle brackets are used, the included makefile is expected to be in the system
     makefile directory.  If double quotes are used, the including makefile's directory and any
     directories specified using the -I option are searched before the system makefile directory.
     For compatibility with other versions of bmake ‘include file ...’ is also accepted.

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

     If the include statement is written as .dinclude not only are errors locating and/or opening
     include files ignored, but stale dependencies within the included file will be ignored just
     like .MAKE.DEPENDFILE.

     Conditional expressions are also preceded by a single dot as the first character of a line.
     The possible conditionals are as follows:

     .error message
             The message is printed along with the name of the makefile and line number, then
             bmake will exit.

     .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 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 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 variable.  Only global variables may be un-defined.

     .unexport variable ...
             The opposite of ‘.export’.  The specified global variable will be removed from
             .MAKE.EXPORTED.  If no variable list is provided, all globals are unexported, and
             .MAKE.EXPORTED deleted.

     .unexport-env
             Unexport all globals previously exported and clear the environment inherited from
             the parent.  This operation will cause a memory leak of the original environment, so
             should be used sparingly.  Testing for .MAKE.LEVEL being 0, would make sense.  Also
             note that any variables which originated in the parent environment should be
             explicitly preserved if desired.  For example:

                   .if ${.MAKE.LEVEL} == 0
                   PATH := ${PATH}
                   .unexport-env
                   .export PATH
                   .endif

             Would result in an environment containing only ‘PATH’, which is the minimal useful
             environment.  Actually ‘.MAKE.LEVEL’ will also be pushed into the new environment.

     .warning message
             The message prefixed by ‘warning:’ is printed along with the name of the makefile
             and line number.

     .if [!]expression [operator expression ...]
             Test the value of an expression.

     .ifdef [!]variable [operator variable ...]
             Test the value of a variable.

     .ifndef [!]variable [operator variable ...]
             Test the value of a variable.

     .ifmake [!]target [operator target ...]
             Test the target being built.

     .ifnmake [!] target [operator target ...]
             Test the target being built.

     .else   Reverse the sense of the last conditional.

     .elif [!] expression [operator expression ...]
             A combination of ‘.else’ followed by ‘.if’.

     .elifdef [!]variable [operator variable ...]
             A combination of ‘.else’ followed by ‘.ifdef’.

     .elifndef [!]variable [operator variable ...]
             A combination of ‘.else’ followed by ‘.ifndef’.

     .elifmake [!]target [operator target ...]
             A combination of ‘.else’ followed by ‘.ifmake’.

     .elifnmake [!]target [operator target ...]
             A combination of ‘.else’ followed by ‘.ifnmake’.

     .endif  End the body of the conditional.

     The operator may be any one of the following:

     ||     Logical OR.

     &&     Logical AND; of higher precedence than “||”.

     As in C, 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 declared the default target
              (either implicitly or explicitly, see .MAIN) before the line containing the
              conditional.

     empty    Takes a variable, with possible modifiers, and evaluates to true if the expansion
              of the variable would result in an empty string.

     exists   Takes a file name as an argument and evaluates to true if the file exists.  The
              file is searched for on the system search path (see .PATH).

     target   Takes a target name as an argument and evaluates to true if the target has been
              defined.

     commands
              Takes a target name as an argument and evaluates to true if the target has been
              defined and has commands associated with it.

     Expression may also be an arithmetic or string comparison.  Variable expansion is performed
     on both sides of the comparison, after which the integral values are compared.  A value is
     interpreted as hexadecimal if it is preceded by 0x, otherwise it is decimal; octal numbers
     are not supported.  The standard C relational operators are all supported.  If after
     variable expansion, either the left or right hand side of a ‘==’ or ‘!=’ operator is not an
     integral value, then string comparison is performed between the expanded variables.  If no
     relational operator is given, it is assumed that the expanded variable is being compared
     against 0 or an empty string in the case of a string comparison.

     When bmake is evaluating one of these conditional expressions, and it encounters a (white-
     space separated) word it doesn't recognize, either the “make” or “defined” expression is
     applied to it, depending on the form of the conditional.  If the form is ‘.ifdef’,
     ‘.ifndef’, or ‘.if’ the “defined” expression is applied.  Similarly, if the form is
     ‘.ifmake’ or ‘.ifnmake, the’ “make” expression is applied.

     If the conditional evaluates to true the parsing of the makefile continues as before.  If it
     evaluates to false, the following lines are skipped.  In both cases this continues until a
     ‘.else’ or ‘.endif’ is found.

     For loops are typically used to apply a set of rules to a list of files.  The syntax of a
     for loop is:

     .for variable [variable ...] in expression
     ⟨make-rules⟩
     .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-rules inside the body of the for loop.  The number of words must
     come out even; that is, if there are three iteration variables, the number of words provided
     must be a multiple of three.

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 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 desired:

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

               The :M pattern suppresses any expansion of the unwanted variable.

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

     .NOTMAIN  Normally 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 figure out how to create
               it, it will ignore this fact and assume the file isn't needed or already exists.

     .PHONY    The target does not correspond to an actual file; it is always considered to be
               out of date, and will not be created with the -t option.  Suffix-transformation
               rules are not applied to .PHONY targets.

     .PRECIOUS
               When bmake 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 bmake's version of a macro.  When the target is used as a
               source for another target, the other target acquires the commands, sources, and
               attributes (except for .USE) of the source.  If the target already has commands,
               the .USE target's commands are appended to them.

     .USEBEFORE
               Exactly like .USE, but prepend the .USEBEFORE target commands to the target.

     .WAIT     If .WAIT appears in a dependency line, the sources that precede it are made before
               the sources that succeed it in the line.  Since the dependents of files are not
               made until the file itself could be made, this also stops the dependents being
               built unless they are needed for another branch of the dependency tree.  So given:

               x: a .WAIT b
                       echo x
               a:
                       echo a
               b: b1
                       echo b
               b1:
                       echo b1

               the output is always ‘a’, ‘b1’, ‘b’, ‘x’.
               The ordering imposed by .WAIT is only relevant for parallel makes.

SPECIAL TARGETS

     Special targets may not be included with other targets, i.e. they must be the only target
     specified.

     .BEGIN   Any command lines attached to this target are executed before anything else is
              done.

     .DEFAULT
              This is sort of a .USE rule for any target (that was used only as a source) that
              bmake 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.

     .END     Any command lines attached to this target are executed after everything else is
              done.

     .ERROR   Any command lines attached to this target are executed when another target fails.
              The .ERROR_TARGET variable is set to the target that failed.  See also
              MAKE_PRINT_VAR_ON_ERROR.

     .IGNORE  Mark each of the sources with the .IGNORE attribute.  If no sources are specified,
              this is the equivalent of specifying the -i option.

     .INTERRUPT
              If 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   The named targets are made in sequence.  This ordering does not add targets to the
              list of targets to be made.  Since the dependents of a target do not get built
              until the target itself could be built, unless ‘a’ is built by another part of the
              dependency graph, the following is a dependency loop:

              .ORDER: b a
              b: a

              The ordering imposed by .ORDER is only relevant for parallel makes.

     .PATH    The sources are directories which are to be searched for files not found in the
              current directory.  If no sources are specified, any previously specified
              directories are deleted.  If the source is the special .DOTLAST target, then the
              current working directory is searched last.

     .PATH.suffix
              Like .PATH but applies only to files with a particular suffix.  The suffix must
              have been previously declared with .SUFFIXES.

     .PHONY   Apply the .PHONY attribute to any specified sources.

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

     .SHELL   Sets the shell that 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 builtin
                          shell specs; sh, ksh, and csh.

              path        Specifies the path to the shell.

              hasErrCtl   Indicates whether the shell supports exit on error.

              check       The command to turn on error checking.

              ignore      The command to disable error checking.

              echo        The command to turn on echoing of commands executed.

              quiet       The command to turn off echoing of commands executed.

              filter      The output to filter after issuing the quiet command.  It is typically
                          identical to quiet.

              errFlag     The flag to pass the shell to enable error checking.

              echoFlag    The flag to pass the shell to enable command echoing.

              newline     The string literal to pass the shell that results in a single newline
                          character when used outside of any quoting characters.
              Example:

              .SHELL: name=ksh path=/bin/ksh hasErrCtl=true \
                      check="set -e" ignore="set +e" \
                      echo="set -v" quiet="set +v" filter="set +v" \
                      echoFlag=v errFlag=e newline="'\n'"

     .SILENT  Apply the .SILENT attribute to any specified sources.  If no sources are specified,
              the .SILENT attribute is applied to every command in the file.

     .STALE   This target gets run when a dependency file contains stale entries, having .ALLSRC
              set to the name of that dependency file.

     .SUFFIXES
              Each source specifies a suffix to 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,
     MACHINE_MULTIARCH, 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 description of ‘.OBJDIR’ for more details.

FILES

     .depend        list of dependencies
     Makefile       list of dependencies
     makefile       list of dependencies
     sys.mk         system makefile
     /usr/share/mk  system makefile directory

COMPATIBILITY

     The basic make syntax is compatible between different versions of make; however the special
     variables, variable modifiers and conditionals are not.

   Older versions
     An incomplete list of changes in older versions of 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 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 bmake 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

     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 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 of the data.  For instance
     finding the end of a variable use should involve scanning each the modifiers using the
     correct terminator for each field.  In many places 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.