<HTML> <TITLE> Jam/MR - Make(1) Redux </TITLE> <BODY> <CENTER> <H1> Jam/MR - Make(1) Redux </H1> <P> The <a href=http://www.perforce.com/jam/jam.html>Jam/MR</a> Executable </CENTER> <DL> <DT> <P> <H2> USAGE </H2> <DD> <PRE> jam [ -a ] [ -n ] [ -v ] [ -d <I>debug</I> ] [ -f <I>jambase</I> ] [ -j <I>jobs</I> ] [ -o <I>actionsfile</I> ] [ -s <I>var</I>=<I>value</I> ] [ -t <I>target</I> ] [ <I>target</I> ... ] </PRE> <DT> <P> <H2> DESCRIPTION </H2> <DD> <P> <B>Jam</B> is a program construction tool, like <B>make</B>(1). <P> <B>Jam</B> recursively builds target files from source files, using dependency information and updating actions expressed in the Jambase file, which is written in <B>jam</B>'s own interpreted language. The default Jambase is compiled into <B>jam</B> and provides a boilerplate for common use, relying on a user-provide file "Jamfile" to enumerate actual targets and sources. <P> The Jambase is described in the <a href="Jambase.html">Jambase Reference</a> and the document <a href="Jamfile.html">Using Jamfiles and Jambase</A>. <DT> <P> <H2> OPTIONS </H2> <DD> <P> If <I>target</I> is provided on the command line, <B>jam</B> builds <I>target;</I> otherwise <B>jam</B> builds the target 'all'. <P> <B>Jam</b> may be invoked with the following options: <P> <TABLE WIDTH=75% ALIGN=CENTER> <TR><TD VALIGN=TOP><CODE> -a </CODE> <TD> Build all targets anyway, even if they are up-to-date. <TR><TD VALIGN=TOP><CODE> -d <I>n</I> </CODE> <TD> Enable cummulative debugging levels from 1 to <I>n</I>. Interesting values are: <DL COMPACT> <DT> 1 <DD> Show actions (the default) <DT> 2 <DD> Show "quiet" actions and display all action text <DT> 3 <DD> Show dependency analysis, and target/source timestamps/paths <DT> 4 <DD> Show shell arguments <DT> 5 <DD> Show rule invocations and variable expansions <DT> 6 <DD> Show directory/header file/archive scans <DT> 7 <DD> Show variable settings <DT> 8 <DD> Show variable fetches <DT> 9 <DD> Show variable manipulation, scanner tokens </DL> <TR><TD VALIGN=TOP><CODE> -d +<I>n</I> </CODE> <TD> Enable debugging level <I>n</I>. <TR><TD VALIGN=TOP><CODE> -d 0 </CODE> <TD> Turn off all debugging levels. Only errors are not suppressed. <TR><TD VALIGN=TOP><CODE> -f <I>jambase</I></CODE> <TD>Read <I>jambase</I> instead of using the built-in Jambase. Only one -f flag is permitted, but the <i>jambase</i> may explicitly include other files. <TR><TD VALIGN=TOP><CODE> -j <I>n</I></CODE> <TD> Run up to <I>n</I> shell commands concurrently (UNIX and NT only). The default is 1. <TR><TD VALIGN=TOP><CODE> -n</CODE> <TD> Don't actually execute the updating actions, but do everything else. This changes the debug level default to -d2. <TR><TD VALIGN=TOP><CODE> -o <I>file</I></CODE> <TD> Write the updating actions to the specified file instead of running them (or outputting them, as on the Mac). <TR><TD VALIGN=TOP><CODE> -s <I>var</I>=<I>value</I></CODE> <TD> Set the variable <I>var</I> to <I>value</I>, overriding both internal variables and variables imported from the environment. <TR><TD VALIGN=TOP><CODE> -t <I>target</I></CODE> <TD> Rebuild <I>target</I> and everything that depends on it, even if it is up-to-date. <TR><TD VALIGN=TOP><CODE> -v</CODE> <TD> Print the version of <B>jam</B> and exit. </TABLE> <DT> <P> <H2> OPERATION </H2> <DD> <P> <b>Jam</b> has four phases of operation: start-up, parsing, binding, and updating. <DT> <P> <H3> Start-up </H3> <DD> <P> Upon start-up, <b>jam</b> imports environment variable settings into <b>jam</b> variables. Environment variables are split at blanks with each word becoming an element in the variable's list of values. Environment variables whose names end in PATH are split at $(SPLITPATH) characters (e.g., ":" for Unix). <P> To set a variable's value on the command line, overriding the variable's environment value, use the -s option. To see variable assignments made during <b>jam</b>'s execution, use the -d+7 option. <DT> <P> <H3> Parsing </H3> <DD> <P> In the parsing phase, <b>jam</b> reads and parses the Jambase file, by default the built-in one. It is written in the <b>jam</b> language. See <a href="#language"> Language</a> below. The last action of the Jambase is to read (via the "include" rule) a user-provided file called "Jamfile". <P> Collectively, the purpose of the Jambase and the Jamfile is to name built target and source files, construct the dependency graph among them, and associate build actions with targets. The Jambase defines boilerplate rules and variable assignments, and the Jamfile uses these to specify the actual relationship among the target and source files. See the <a href="Jambase.html">Jambase Reference</a> and the document <a href="Jamfile.html">Using Jamfiles and Jambase</A> for information. <A NAME="binding"> <DT> <P> <H3> Binding </H3> <DD> </A> <P> <P> <H5> Binding </H5> After parsing, <B>jam</B> recursively descends the dependency graph and binds every file target with a location in the filesystem. If <B>jam</B> detects a circular dependency in the graph, it issues a warning. <P> File target names are given as absolute or relative path names in the filesystem. If the path name is absolute, it is bound as is. If the path name is relative, it is normally bound as is, and thus relative to the current directory. This can be modified by the settings of the $(SEARCH) and $(LOCATE) variables, which enable <b>jam</b> to find and build targets spread across a directory tree. See <A HREF="#search">SEARCH and LOCATE Variables</a> below. <P> <H5> Update Determination </H5> After binding each target, <B>jam</B> determines whether the target needs updating, and if so marks the target for the updating phase. A target is normally so marked if it is missing, it is older than any of its sources, or any of its sources are marked for updating. This behavior can be modified by the application of special built-in rules, ALWAYS, LEAVES, NOCARE, NOTFILE, NOUPDATE, and TEMPORARY. See <A HREF="#bindingmods">Modifying Binding</A> below. <P> <H5> Header File Scanning </H5> <P> During the binding phase, <b>jam</b> also performs header file scanning, where it looks inside source files for the implicit dependencies on other files caused by C's #include syntax. This is controlled by the special variables $(HDRSCAN) and $(HDRRULE). The result of the scan is formed into a rule invocation, with the scanned file as the target and the found included file names as the sources. Note that this is the only case where rules are invoked outside the parsing phase. See <A HREF="#hdrscan">HDRSCAN and HDRRULE Variables</A> below. <DT> <P> <H3> Updating </H3> <DD> <P> After binding, <B>jam</B> again recursively descends the dependency graph, this time executing the update actions for each target marked for update during the binding phase. If a target's updating actions fail, then all other targets which depend on that target are skipped. <P> The -j flag instructs <B>jam</B> to build more than one target at a time. If there are multiple actions on a single target, they are run sequentially. <A NAME="language"> <DT> <P> <H2> LANGUAGE </H2> <DD> </A> <DT> <P> <H3> Overview </H3> <DD> <B>Jam</b> has an interpreted, procedural language. Statements in <b>jam</b> are rule (procedure) definitions, rule invocations, flow-of-control structures, variable assignments, and sundry language support. <DT> <P> <H3> Lexical Features </H3> <DD> <P> <B>Jam</b> treats its input files as whitespace-separated tokens, with two exceptions: double quotes (") can enclose whitespace to embed it into a token, and everything between the matching curly braces ({}) in the definition of a rule action is treated as a single string. A backslash (\) can escape a double quote, or any single whitespace character. <P> <B>Jam</b> requires whitespace (blanks, tabs, or newlines) to surround all tokens, <i>including the colon (:) and semicolon (;) tokens</i>. <P> <B>Jam</b> keywords (an mentioned in this document) are reserved and generally must be quoted with double quotes (") to be used as arbitrary tokens, such as variable or target names. <DT> <P> <H3> Targets </H3> <DD> <P> The essential <b>jam</b> data entity is a target. Built targets are files to be updated. Source targets are the files used in updating built targets. Built targets and source targets are collectively referred to as file targets, and frequently built targets are source targets for other built targets. Pseudotargets are symbols which represent dependencies on other targets, but which are not themselves associated with any real file. <P> A file target's identifier is generally the file's name, which can be absolutely rooted, relative to the directory of <b>jam</b>'s invocation, or simply local (no directory). Most often it is the last case, and the actual file path is bound using the $(SEARCH) and $(LOCATE) special variables. See <A HREF="#search"> SEARCH and LOCATE Variables</A> below. A local filename is optionally qualified with grist, a string value used to assure uniqueness. A file target with an identifier of the form <I>file(member)</I> is a library member (usually an ar(1) archive on UNIX). <DT> <P> <H3> Rules </H3> <DD> <P> The basic <B>jam</b> language entity is called a rule. A rule is defined in two parts: the procedure and the actions. The procedure is a body of <b>jam</b> statements to be run when the rule is invoked; the actions are the OS shell commands to execute when updating the built targets of the rule. <P> Rules can return values, which can be expanded into a list with "[ <i>rule</i> <i>args</i> ... ]". A rule's value is the value of its last statement, though only the following statements have values: 'if' (value of the leg chosen), 'switch' (value of the case chosen), set (value of the resulting variable), and 'return' (value of its arguments). Note that 'return' doesn't actually cause a return, i.e., is a no-op unless it is the last statement of the last block executed within rule body. <P> The <b>jam</b> statements for defining and invoking rules are as follows: <P><TABLE WIDTH=75% ALIGN=CENTER><TR><TD><DL> <P> <DT> <CODE> rule <I>rulename</I> { <I>statements</I> } </CODE> <DD> Define a rule's procedure, replacing any previous definition. <P> <DT> <CODE> actions [ <I>modifiers</I> ] <I>rulename</I> { <I>commands</I> } </CODE> <DD> Define a rule's updating actions, replacing any previous definition. <P> <DT> <CODE> <I>rulename field1</I> : <I>field2</I> : <I>...</I> : <I>fieldN</I> ; </CODE> <DD> Invoke a rule. <P> <DT> <CODE> on <I>target</I> <I>rulename field1</I> : <I>field2</I> : <I>...</I> : <I>fieldN</I> ; </CODE> <DD> Invoke a rule under the influence of <I>target</I>'s specific variables.. <P> <DT> <CODE> [ <I>rulename field1</I> : <I>field2</I> : <I>...</I> : <I>fieldN</I> ] <br> [ on <I>target</I> <I>rulename field1</I> : <I>field2</I> : <I>...</I> : <I>fieldN</I> ] <br> </CODE> <DD> Used as an argument, expands to the return value of the rule invoked. </DL></TABLE> <P> A rule is invoked with values in <I>field1</I> through <I>fieldN</I>. They may be referenced in the procedure's <I>statements</I> as $(1) through $(<I>N</I>) (9 max), and the first two only may be referenced in the action's <I>commands</I> as $(1) and $(2). $(<) and $(>) are synonymous with $(1) and $(2). <P> Rules fall into two categories: updating rules (with actions), and pure procedure rules (without actions). Updating rules treat arguments $(1) and $(2) as built targets and sources, respectively, while pure procedure rules can take arbitrary arguments. <P> When an updating rule is invoked, its updating actions are added to those associated with its built targets ($(1)) before the rule's procedure is run. Later, to build the targets in the updating phase, <I>commands</I> are passed to the OS command shell, with $(1) and $(2) replaced by bound versions of the target names. See <A HREF="#binding"> Binding</A> above. <P> <A NAME="actionmods"> <P> <H4> Action Modifiers </H4> </A> <P> The following action <i>modifiers</i> are understood: <P><TABLE WIDTH=75% ALIGN=CENTER><TR><TD><DL> <P><DT><CODE> actions bind <I>vars</I> </CODE> <DD> $(vars) will be replaced with bound values. <P><DT><CODE> actions existing </CODE> <DD> $(>) includes only source targets currently existing. <P><DT><CODE> actions ignore </CODE> <DD> The return status of the <I>commands</I> is ignored. <P><DT><CODE> actions piecemeal </CODE> <DD> <I>commands</I> are repeatedly invoked with a subset of $(>) small enough to fit in the command buffer on this OS. <P><DT><CODE> actions quietly </CODE> <DD> The action is not echoed to the standard output. <P><DT><CODE> actions together </CODE> <DD> The $(>) from multiple invocations of the same action on the same built target are glommed together. <P><DT><CODE> actions updated </CODE> <DD> $(>) includes only source targets themselves marked for updating. </DL></TABLE> <DT> <P> <H3> Built-in Rules </H3> <DD> <P> <B>Jam</b> has eleven built-in rules, all of which are pure procedure rules without updating actions. They are in three groups: the first builds the dependency graph; the second modifies it; and the third are just utility rules. <P> <P> <H5> Dependency Building </H5> <P><TABLE WIDTH=75% ALIGN=CENTER><TR><TD><DL> <P><DT><CODE> DEPENDS <I>targets1</I> : <I>targets2</I> ; </CODE> <DD> Builds a direct dependency: makes each of <I>targets1</I> depend on each of <I>targets2</I>. Generally, <I>targets1</I> will be rebuilt if <I>targets2</I> are themselves rebuilt are or are newer than <I>targets1</I>. <P><DT><CODE> INCLUDES <I>targets1</I> : <I>targets2</I> ; </CODE> <DD> Builds a sibling dependency: makes any target that depends on any of <I>targets1</I> also depend on each of <I>targets2</I>. This reflects the dependencies that arise when one source file includes another: the object built from the source file depends both on the original and included source file, but the two sources files don't depend on each other. For example: <CODE> <P>DEPENDS foo.o : foo.c ; <BR>INCLUDES foo.c : foo.h ; </CODE> <P> "foo.o" depends on "foo.c" and "foo.h" in this example. </DL></TABLE> <A NAME="bindingmods"> <P> <H5> Modifying Binding </H5> </A> <P> The six rules ALWAYS, LEAVES, NOCARE, NOTFILE, NOUPDATE, and TEMPORARY modify the dependency graph so that <b>jam</b> treats the targets differently during its target binding phase. See <A HREF="#binding">Binding</A> above. Normally, <b>jam</b> updates a target if it is missing, if its filesystem modification time is older than any of its dependencies (recursively), or if any of its dependencies are being updated. This basic behavior can be changed by invoking the following rules: <P><TABLE WIDTH=75% ALIGN=CENTER><TR><TD><DL> <P><DT><CODE> ALWAYS <I>targets</I> ; </CODE> <DD> Causes <I>targets</I> to be rebuilt regardless of whether they are up-to-date (they must still be in the dependency graph). This is used for the clean and uninstall targets, as they have no dependencies and would otherwise appear never to need building. It is best applied to targets that are also NOTFILE targets, but it can also be used to force a real file to be updated as well. <P><DT><CODE> LEAVES <I>targets</I> ; </CODE> <DD> Makes each of <I>targets</I> depend only on its leaf sources, and not on any intermediate targets. This makes it immune to its dependencies being updated, as the "leaf" dependencies are those without their own dependencies and without updating actions. This allows a target to be updated only if original source files change. <P><DT><CODE> NOCARE <I>targets</I> ; </CODE> <DD> Causes <b>jam</b> to ignore <I>targets</I> that neither can be found nor have updating actions to build them. Normally for such targets <B>jam</B> issues a warning and then skips other targets that depend on these missing targets. The HdrRule in Jambase uses NOCARE on the header file names found during header file scanning, to let <b>jam</b> know that the included files may not exist. For example, if a #include is within an #ifdef, the included file may not actually be around. <P><DT><CODE> NOTFILE <I>targets</I> ; </CODE> <DD> Marks <I>targets</I> as pseudotargets and not real files. No timestamp is checked, and so the actions on such a target are only executed if the target's dependencies are updated, or if the target is also marked with ALWAYS. The default <b>jam</b> target "all" is a pseudotarget. In Jambase, NOTFILE is used to define several addition convenient pseudotargets. <P><DT><CODE> NOUPDATE <I>targets</I> ; </CODE> <DD> Causes the timestamps on <I>targets</I> to be ignored. This has two effects: first, once the target has been created it will never be updated; second, manually updating target will not cause other targets to be updated. In Jambase, for example, this rule is applied to directories by the MkDir rule, because MkDir only cares that the target directory exists, not when it has last been updated. <P><DT><CODE> TEMPORARY <I>targets</I> ; </CODE> <DD> Marks <I>targets</I> as temporary, allowing them to be removed after other targets that depend upon them have been updated. If a TEMPORARY target is missing, <b>jam</b> uses the timestamp of the target's parent. Jambase uses TEMPORARY to mark object files that are archived in a library after they are built, so that they can be deleted after they are archived. </DL></TABLE> <P> <H5> Utility Rules </H5> <P> The two rules ECHO and EXIT are utility rules, used only in <b>jam</b>'s parsing phase. <P><TABLE WIDTH=75% ALIGN=CENTER><TR><TD><DL> <P><DT><CODE> ECHO <i>args</I> ; </CODE> <DD> Blurts out the message <i>args</I> to stdout. <P><DT><CODE> EXIT <i>args</I> ; </CODE> <DD> Blurts out the message <i>args</I> to stdout and then exits with a failure status. <P> "Echo", "echo", "Exit", and "exit" are accepted as aliases for ECHO and EXIT, since it is hard to tell that these are built-in rules and not part of the language, like "include". </DL></TABLE> <P> The GLOB rule does filename globbing. <P><TABLE WIDTH=75% ALIGN=CENTER><TR><TD><DL> <P><DT><CODE> GLOB <i>directories</I> : <I>patterns</I> </CODE> <DD> Using the same wildcards as for the patterns in the <A HREF="#switch">switch</A> statement). It is invoked by being used as an argument to a rule invocation inside of `[ ]`. For example: "FILES = [ GLOB dir1 dir2 : *.c *.h ]" will set the value of A to the list of C source and header files in dir1 or dir2. </DL></TABLE> <DT> <P> <H3> Flow-of-Control </H3> <DD> <P> Jam has several simple flow-of-control statements: <P><TABLE WIDTH=75% ALIGN=CENTER><TR><TD><DL> <P><DT><CODE> for <I>var</I> in <I>list</I> { <I>statements</I> } </CODE> <P><DD> Executes <i>statements</i> for each element in <i>list</i>, setting the variable <i>var</i> to the element value. <A name=if> <P><DT><CODE> </A> if <I>cond</I> { <I>statements</I> } <BR> [ else <I>statements</I> ] </CODE> <P><DD> Does the obvious; the else clause is optional. <i>cond</i> is built of: <TABLE> <TR><TD> <CODE><I>a</I></CODE></TD> <TD> true if any <I>a</I> element is a non-zero-length string</TD> <TR><TD> <CODE><I>a</I> = <I>b</I></CODE> </TD> <TD> list <I>a</I> matches list <I>b</I> string-for-string</TD> <TR><TD> <CODE><I>a</I> != <I>b</I> </CODE></TD> <TD> list <I>a</I> does not match list <I>b</I></TD> <TR><TD> <CODE><I>a</I> < <I>b</I> </CODE></TD> <TD> <I>a[i]</I> string is less than <I>b[i]</I> string, where <i>i</i> is first mismatched element in lists <I>a</I> and <I>b</I></TD> <TR><TD> <CODE><I>a</I> <= <I>b</I> </CODE></TD> <TD> every <I>a</I> string is less than or equal to its <I>b</I> counterpart</TD> <TR><TD> <CODE><I>a</I> > <I>b</I> </CODE></TD> <TD> <I>a[i]</I> string is greater than <I>b[i]</I> string, where <i>i</i> is first mismatched element</TD> <TR><TD> <CODE><I>a</I> >= <I>b</I> </CODE></TD> <TD> every <I>a</I> string is greater than or equal to its <I>b</I> counterpart</TD> <TR><TD> <CODE><I>a</I> in <I>b</I> </CODE></TD> <TD> true if all elements of <I>a</I> can be found in <I>b</I>, or if <I>a</I> has no elements</TD> <TR><TD> <CODE>! <I>cond</I> </CODE></TD> <TD> condition not true</TD> <TR><TD> <CODE><I>cond</I> && <I>cond</I> </CODE></TD> <TD> conjunction</TD> <TR><TD> <CODE><I>cond</I> || <I>cond</I> </CODE></TD> <TD> disjunction</TD> <TR><TD> <CODE>( <I>cond</I> ) </CODE></TD> <TD> precedence grouping</TD> </TABLE> <P><DT> <CODE> include <I>file</I> ; </CODE> <P><DD> Causes <b>jam</b> to read the named <i>file</i>. The file is bound like a regular target (see <A HREF="#binding"> Binding</A> above) but unlike a regular target the include file cannot be built. <P> The include file is inserted into the input stream during the parsing phase. The primary input file and all the included file(s) are treated as a single file; that is, <b>jam</b> infers no scope boundaries from included files. <P><DT> <CODE> local <i>vars</I> [ = <i>values</i> ] ; </CODE> <P><DD> Creates new <i>vars</i> inside to the enclosing {} block, obscuring any previous values they might have. The previous values for <i>vars</i> are restored when the current block ends. Any rule called or file included will see the local and not the previous value (this is sometimes called Dynamic Scoping). The local statement may appear anywhere, even outside of a block (in which case the previous value is restored when the input ends). The <i>vars</i> are initialized to <i>values</i> if present, or left uninitialized otherwise. <P><DT> <CODE> return <I>values</I> ; </CODE> <P><DD> Within a rule body, the return statement sets the return value for an invocation of the rule. It does <i>not</i> cause the rule to return; a rule's value is actually the value of the last statement executed, so a return should be the last statement executed before the rule "naturally" returns. <P><DT> <CODE> <A NAME="switch"> switch <I>value</I> </A> <BR> { <BR> case <I>pattern1</I> : <I>statements</I> ; <BR> case <I>pattern2</I> : <I>statements</I> ; <BR> ... <BR> } </CODE> <P><DD> The switch statement executes zero or one of the enclosed <i>statements</i>, depending on which, if any, is the first case whose <i>pattern</I> matches <i>value</i>. The <i>pattern</I> values are not variable-expanded. The <i>pattern</I> values may include the following wildcards: <TABLE> <TR><TD><CODE> ? </CODE></TD> <TD> match any single character </TD> <TR><TD><CODE> * </CODE></TD> <TD> match zero or more characters </TD> <TR><TD><CODE> [<i>chars</i>] </CODE></TD> <TD> match any single character in <i>chars</i> </TD> <TR><TD><CODE> [^<i>chars</i>] </CODE></TD> <TD> match any single character not in <i>chars</i> </TD> <TR><TD><CODE> \<i>x</i> </CODE></TD> <TD> match <i>x</i> (escapes the other wildcards)</i> </TD> </TABLE> <P><DT> <CODE> while <I>cond</I> { <I>statements</I> } </CODE> <P><DD> Repeatedly execute <I>statements</I> while <I>cond</I> remains true upon entry. (See the description of <I>cond</I> expression syntax under <a href="#if">if</a>, above). </DL></TABLE> <DT> <P> <H3> Variables </H3> <DD> <P> <B>Jam</b> variables are lists of zero or more elements, with each element being a string value. An undefined variable is indistinguishable from a variable with an empty list, however, a defined variable may have one more elements which are null strings. All variables are referenced as $(<I>variable</I>). <P> Variables are either global or target-specific. In the latter case, the variable takes on the given value only during the updating of the specific target. <P> A variable is defined with: <P> <TABLE WIDTH=75% ALIGN=CENTER> <TR><TD> <DL> <DT><CODE> <I>variable</I> = <I>elements</I> ; </CODE> <DT><CODE> <I>variable</I> += <I>elements</I> ; </CODE> <DT><CODE> <I>variable</I> on <I>targets</I> = <I>elements</I> ; </CODE> <DT><CODE> <I>variable</I> on <I>targets</I> += <I>elements</I> ; </CODE> <DT><CODE> <I>variable</I> default = <I>elements</I> ; </CODE> <DT><CODE> <I>variable</I> ?= <I>elements</I> ; </CODE> </DL></TABLE> <P> The first two forms set <I>variable</I> globally. The third and forth forms set a target-specific variable. The = operator replaces any previous elements of <I>variable</I> with <I>elements</I>; the += operation adds <I>elements</I> to <I>variable</I>'s list of elements. The final two forms are synonymous: they set <I>variable</I> globally, but only if it was previously unset. <P> Variables referenced in updating commands will be replaced with their values; target-specific values take precedence over global values. Variables passed as arguments ($(1) and $(2)) to actions are replaced with their bound values; the "bind" modifier can be used on actions to cause other variables to be replaced with bound values. See <A HREF="#actionmods">Action Modifiers</A> above. <P> <B>Jam</b> variables are not re-exported to the environment of the shell that executes the updating actions, but the updating actions can reference <b>jam</b> variables with $(<I>variable</I>). <P> <H4> Variable Expansion </H4> <P> During parsing, <b>jam</b> performs variable expansion on each token that is not a keyword or rule name. Such tokens with embedded variable references are replaced with zero or more tokens. Variable references are of the form $(<I>v</I>) or $(<I>vm</I>), where <i>v</i> is the variable name, and <I>m</I> are optional modifiers. <P> Variable expansion in a rule's actions is similar to variable expansion in statements, except that the action string is tokenized at whitespace regardless of quoting. <P> The result of a token after variable expansion is the <i>product</i> of the components of the token, where each component is a literal substring or a list substituting a variable reference. For example: <P> <TABLE WIDTH=75% ALIGN=CENTER><TR><TD><CODE> <BR>$(X) -> a b c <BR>t$(X) -> ta tb tc <BR>$(X)z -> az bz cz <BR>$(X)-$(X) -> a-a a-b a-c b-a b-b b-c c-a c-b c-c </CODE></TABLE> <P> The variable name and modifiers can themselves contain a variable reference, and this partakes of the product as well: <P> <TABLE WIDTH=75% ALIGN=CENTER><TR><TD><CODE> <BR>$(X) -> a b c <BR>$(Y) -> 1 2 <BR>$(Z) -> X Y <BR>$($(Z)) -> a b c 1 2 </CODE></TABLE> <P> Because of this product expansion, if any variable reference in a token is undefined, the result of the expansion is an empty list. If any variable element is a null string, the result propagates the non-null elements: <P> <TABLE WIDTH=75% ALIGN=CENTER><TR><TD><CODE> <BR>$(X) -> a "" <BR>$(Y) -> "" 1 <BR>$(Z) -> <BR>*$(X)$(Y)* -> *a* *a1* ** *1* <BR>*$(X)$(Z)* -> </CODE></TABLE> <P> A variable element's string value can be parsed into grist and filename-related components. Modifiers to a variable are used to select elements, select components, and replace components. The modifiers are: <P> <TABLE WIDTH=75% ALIGN=CENTER> <TR><TD><CODE> [<I>n</I>] </CODE> <TD>Select element number <I>n</I> (starting at 1). If the variable contains fewer than <I>n</I> elements, the result is a zero-element list. <TR><TD><CODE> [<I>n</I>-<I>m</I>] </CODE> <TD>Select elements number <I>n</I> through <I>m</I>. <TR><TD><CODE> [<I>n</I>-] </CODE> <TD>Select elements number <I>n</I> through the last. <TR><TD><CODE> :B </CODE> <TD>Select filename base. <TR><TD><CODE> :S </CODE> <TD>Select (last) filename suffix. <TR><TD><CODE> :M </CODE> <TD>Select archive member name. <TR><TD><CODE> :D </CODE> <TD>Select directory path. <TR><TD><CODE> :P </CODE> <TD>Select parent directory. <TR><TD><CODE> :G </CODE> <TD>Select grist. <TR><TD><CODE> :U </CODE> <TD>Replace lowercase characters with uppercase. <TR><TD><CODE> :L </CODE> <TD>Replace uppercase characters with lowercase. <TR><TD><CODE> :<i>chars</I> </CODE> <TD>Select the components listed in <i>chars</i>. <TR><TD><CODE> :G=<I>grist</I> </CODE> <TD>Replace grist with <I>grist</I>. <TR><TD><CODE> :D=<I>path</I> </CODE> <TD>Replace directory with <I>path</I>. <TR><TD><CODE> :B=<I>base</I> </CODE> <TD>Replace the base part of file name with <I>base</I>. <TR><TD><CODE> :S=<I>suf</I> </CODE> <TD>Replace the suffix of file name with <I>suf</I>. <TR><TD><CODE> :M=<I>mem</I> </CODE> <TD>Replace the archive member name with <I>mem</I>. <TR><TD><CODE> :R=<I>root</I> </CODE> <TD>Prepend <I>root</I> to the whole file name, if not already rooted. <TR><TD><CODE> :E=<I>value</I> </CODE> <TD>Assign <I>value</I> to the variable if it is unset. <TR><TD><CODE> :J=<I>joinval</I> </CODE> <TD>Concatentate list elements into single element, separated by <I>joinval</I>. </TABLE> <P> On VMS, $(var:P) is the parent directory of $(var:D); on Unix and NT, $(var:P) and $(var:D) are the same. <DT> <P> <H3> Built-in Variables </H3> <DD> <P> This section discusses variables that have special meaning to <b>jam</b>. <A NAME="search"> <P> <H4> SEARCH and LOCATE Variables </H4> </A> <P> These two variables control the binding of file target names to locations in the file system. Generally, $(SEARCH) is used to find existing sources while $(LOCATE) is used to fix the location for built targets. <P> Rooted (absolute path) file targets are bound as is. Unrooted file target names are also normally bound as is, and thus relative to the current directory, but the settings of $(LOCATE) and $(SEARCH) alter this: <P> <UL> <LI> If $(LOCATE) is set then the target is bound relative to the first directory in $(LOCATE). Only the first element is used for binding. <LI> If $(SEARCH) is set then the target is bound to the first directory in $(SEARCH) where the target file already exists. <LI> If the $(SEARCH) search fails, the target is bound relative to the current directory anyhow. </UL> <P> Both $(SEARCH) and $(LOCATE) should be set target-specific and not globally. If they were set globally, <b>jam</b> would use the same paths for all file binding, which is not likely to produce sane results. When writing your own rules, especially ones not built upon those in Jambase, you may need to set $(SEARCH) or $(LOCATE) directly. Almost all of the rules defined in Jambase set $(SEARCH) and $(LOCATE) to sensible values for sources they are looking for and targets they create, respectively. <A NAME="hdrscan"> <P> <H4> HDRSCAN and HDRRULE Variables </H4> </A> <P> These two variable control header file scanning. $(HDRSCAN) is an <b>egrep</b>(1) pattern, with ()'s surrounding the file name, used to find file inclusion statements in source files. Jambase uses $(HDRPATTERN) as the pattern for $(HDRSCAN). $(HDRRULE) is the name of a rule to invoke with the results of the scan: the scanned file is the target, the found files are the sources. This is the only place where <b>jam</b> invokes a rule through a variable setting. <P> Both $(HDRSCAN) and $(HDRRULE) must be set for header file scanning to take place, and they should be set target-specific and not globally. If they were set globally, all files, including executables and libraries, would be scanned for header file include statements. <P> The scanning for header file inclusions is not exact, but it is at least dynamic, so there is no need to run something like <b>makedepend</b>(GNU) to create a static dependency file. The scanning mechanism errs on the side of inclusion (i.e., it is more likely to return filenames that are not actually used by the compiler than to miss include files) because it can't tell if #include lines are inside #ifdefs or other conditional logic. In Jambase, HdrRule applies the NOCARE rule to each header file found during scanning so that if the file isn't present yet doesn't cause the compilation to fail, <b>jam</b> won't care. <P> Also, scanning for regular expressions only works where the included file name is literally in the source file. It can't handle languages that allow including files using variable names (as the Jam language itself does). <P> <H4> Platform Identifier Variables </H4> <P> A number of Jam built-in variables can be used to identify runtime platform: <P> <TABLE WIDTH=75% ALIGN=CENTER> <TR><TD>OS<TD>OS identifier string <TR><TD>OSPLAT<TD>Underlying architecture, when applicable <TR><TD>MAC<TD>true on MAC platform <TR><TD>NT<TD>true on NT platform <TR><TD>OS2<TD>true on OS2 platform <TR><TD>UNIX<TD>true on Unix platforms <TR><TD>VMS<TD>true on VMS platform </TABLE> <P> <H4> Jam Version Variables </H4> <P> <TABLE WIDTH=75% ALIGN=CENTER> <TR><TD>JAMDATE<TD>Time and date at <b>jam</b> start-up. <TR><TD>JAMUNAME<TD>Ouput of <b>uname</b>(1) command (Unix only) <TR><TD>JAMVERSION<TD><b>jam</b> version, currently "2.3" </TABLE> <P> <H4> JAMSHELL Variable </H4> <P> When <b>jam</b> executes a rule's action block, it forks and execs a shell, passing the action block as an argument to the shell. The invocation of the shell can be controlled by $(JAMSHELL). The default on Unix is, for example: <P> <CODE>JAMSHELL = /bin/sh -c % ;</CODE> <P> The % is replaced with the text of the action block. <P> <B>Jam</b> does not directly support building in parallel across multiple hosts, since that is heavily dependent on the local environment. To build in parallel across multiple hosts, you need to write your own shell that provides access to the multiple hosts. You then reset $(JAMSHELL) to reference it. <P> Just as <b>jam</b> expands a % to be the text of the rule's action block, it expands a ! to be the multi-process slot number. The slot number varies between 1 and the number of concurrent jobs permitted by the -j flag given on the command line. Armed with this, it is possible to write a multiple host shell. For example: <P> <TABLE WIDTH=75% ALIGN=CENTER><TR><TD><CODE> <BR>#!/bin/sh <BR> <BR># This sample JAMSHELL uses the SunOS on(1) command to execute a <BR># command string with an identical environment on another host. <BR> <BR># Set JAMSHELL = jamshell ! % <BR># <BR># where jamshell is the name of this shell file. <BR># <BR># This version handles up to -j6; after that they get executed <BR># locally. <BR> <BR>case $1 in <BR>1|4) on winken sh -c "$2";; <BR>2|5) on blinken sh -c "$2";; <BR>3|6) on nod sh -c "$2";; <BR>*) eval "$2";; <BR>esac </CODE></TABLE> <DT> <P> <H2> DIAGNOSTICS </H2> <DD> <P> In addition to generic error messages, <B>jam</B> may emit one of the following: <P><TABLE WIDTH=75% ALIGN=CENTER><TR><TD><DL> <P><DT><CODE> warning: unknown rule X </CODE> <DD> A rule was invoked that has not been defined with an "actions" or "rule" statement. <P><DT><CODE> using N temp target(s) </CODE> <DD> Targets marked as being temporary (but nonetheless present) have been found. <P><DT><CODE> updating N target(s) </CODE> <DD> Targets are out-of-date and will be updated. <P><DT><CODE> can't find N target(s) </CODE> <DD> Source files can't be found and there are no actions to create them. <P><DT><CODE> can't make N target(s) </CODE> <DD> Due to sources not being found, other targets cannot be made. <P><DT><CODE> warning: X depends on itself </CODE> <DD> A target depends on itself either directly or through its sources. <P><DT><CODE> don't know how to make X </CODE> <DD> A target is not present and no actions have been defined to create it. <P><DT><CODE> X skipped for lack of Y </CODE> <DD> A source failed to build, and thus a target cannot be built. <P><DT><CODE> warning: using independent target X </CODE> <DD> A target that is not a dependency of any other target is being referenced with $(<) or $(>). <P><DT><CODE> X removed </CODE> <DD> <b>Jam</b> removed a partially built target after being interrupted. </DL></TABLE> <DT> <P> <H2> BUGS, LIMITATIONS </H2> <DD> <P> The -j flag can cause <B>jam</B> to get confused when single actions update more than one target at a time. <B>jam</B> may proceed as if the targets were built even though they are still under construction. <P> For parallel building to be successful, the dependencies among files must be properly spelled out, as targets tend to get built in a quickest-first ordering. Also, beware of un-parallelizable commands that drop fixed-named files into the current directory, like <b>yacc</b>(1) does. <P> With the -j flag, errors from failed commands can get staggeringly mixed up. <P> A poorly set $(JAMSHELL) is likely to result in silent failure. <DT> <P> <H2> SEE ALSO </H2> <DD> <P> <UL> <LI> <a href="Jambase.html">Jambase Reference</a> <LI> <a href="Jamfile.html">Using Jamfiles and Jambase</a> </UL> <P> Jam documentation and source are available from the <A HREF="http://public.perforce.com/public/index.html">Perforce Public Depot</a>. <DT> <P> <H2> AUTHOR </H2> <DD> <P> Jam's author is Christopher Seiwald (<a href="mailto:seiwald@perforce.com">seiwald@perforce.com</A>). Documentation is provided by <A HREF="http://www.perforce.com">Perforce Software, Inc.</A> </DL> <P> <HR> <P> Copyright 1993-2002 Christopher Seiwald and Perforce Software, Inc. <BR> Comments to <A HREF="mailto:info@perforce.com">info@perforce.com</A> <BR> Last updated: December 31, 2000 <BR> $Id: //guest/richard_geiger/intjam/src/Jam.html#14 $ </BODY> </HTML>
# | Change | User | Description | Committed | |
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#14 | 1317 | Richard Geiger |
Update the copyright notices in all files touched in the upcoming drop into //public/jam/ |
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#13 | 1315 | Richard Geiger | Changes preparing for an integrate back into //pubic/jam/... | ||
#12 | 1311 | Richard Geiger |
Fix doc on INCLUDES meaning and example. === computer.perforce.com:1666: Change 23681 by seiwald@golly-seiwald on 2001/06/12 17:20:00 |
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#11 | 1306 | Richard Geiger |
Experimental support for '[ on target rule ]' in jam, so that you can access target-specific variables. It is crunchy right now, in that the list of things you can do inside []'s is limited to (a) user-defined rules and (b) the "return" statement. === computer.perforce.com:1666: Change 21437 by seiwald@golly-seiwald on 2001/03/23 10:43:34 Tweaked my earlier version of documenting [ rule ] to explicitly show both forms ( [ rule ... ] and [ on targ rule ... ] ) - rmg |
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#10 | 1295 | Richard Geiger |
Support for 'while' statement in jam. Useful? Who knows. === computer.perforce.com:1666: Change 20250 by seiwald@golly-seiwald on 2001/01/24 15:54:02 Documented in Jam.html - rmg |
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#9 | 1257 | Richard Geiger | Tweak the description of "return". | ||
#8 | 1256 | Richard Geiger |
Support for $(X:J=joinval), which concatenates the lists elements into a single element, separated by (optional) joinval. === computer.perforce.com:1666: Change 19999 by seiwald@golly-seiwald on 2001/01/11 08:35:05 Document :J modifier in Jam.html - rmg |
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#7 | 1255 | Richard Geiger |
Mention that $(N) only works for N = 1 .. 9 when referring to rule arguments. === computer.perforce.com:1666: Change 19998 by seiwald@golly-seiwald on 2001/01/11 08:22:52 |
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#6 | 1249 | Richard Geiger |
Support for $(X:E=emptyvalue), a default value to be used if variable X is unset. === computer.perforce.com:1666: Change 19997 by seiwald@golly-seiwald on 2001/01/11 08:22:15 Add about E:=value to Jam.html. The changes to expand.c look more extensive than I'd have expected for It _could_ just be a code reorg, but it might be worth taking a closer look to make sure nothing else changed (and should be added to the docs) - rmg |
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#5 | 1247 | Richard Geiger |
Fix jam's scanner to allow \ to escape a whitespace char. === computer.perforce.com:1666: Change 19984 by seiwald@golly-seiwald on 2001/01/10 14:07:35 Add note about \-whitespace escape to Jam.html. |
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#4 | 1244 | Richard Geiger |
New 'Glob' builtin that returns a list of files in a list of directories, given a list of patterns. === computer.perforce.com:1666: Change 19941 by seiwald@spice on 2001/01/08 23:32:00 Also, document the existence of rule values, the [ rule args ... ] syntax for accessing them, and the 'return' statement. |
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#3 | 1242 | Richard Geiger |
Jam aliases 'echo' and 'exit' for 'Echo' and 'Exit', since they seem more part of the language than the other built-in rules. === computer.perforce.com:1666: Change 19940 by seiwald@spice2 on 2001/01/08 23:29:35 Added a note about this to Jam.html - rmg |
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#2 | 1237 | Richard Geiger |
Experimental support for running a rule under the influence of a target's specific variables. === computer.perforce.com:1666: Change 19932 by seiwald@spice on 2001/01/08 15:48:36 This feature is now considered part of the language, i.e., no longer experimental. Hence, I have also updated Jam.html and the RELNOTES. - rmg |
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#1 | 1207 | Richard Geiger | Establish this branch to use for import of Perforce Jam. | ||
//guest/perforce_software/jam/src/Jam.html | |||||
#5 | 486 | Perforce staff |
Jam 2.3. See RELNOTES for a list of changes from 2.2.x. Just about every source file was touched when jam got ANSI-fied. |
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#4 | 212 | Perforce staff |
An interpretative integration of Peter Glasscock's -o file support. This is handled in the make1() routine, rather than in all the exec*.c files. -o x writes the actions to file x rather than actually running them. Implies -n (but not -d2). |
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#3 | 76 | Laura Wingerd |
Integrate command-block-too-long fix, plus minor doc updates. Jam/MR release level is now 2.2.5. (change 72, change 73, change 74, change 75) |
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#2 | 51 | Laura Wingerd | Update copyright year. | ||
#1 | 2 | laura | Add Jam/MR 2.2 source |