Introduction
tclmake works on exactly the same principles as make. A makefile contains rules, which specify which files are used to produced which other files, and commands, which are executed to update files. Here is a sample rule and command:
tclIndex: main.tcl parse.tcl update.tcl
auto_mkindex [pwd] main.tcl parse.tcl update.tcl
The files on the left-hand side of a rule are called
targets, and those on the right are called
dependencies. In this case, the target is
tclIndex, and the dependencies are the three
Tcl files.
The job of tclmake is to see if any of the targets are out of date, and if they are, to update them. For example, if tclmake is invoked with
tclmake tclIndex
then tclmake looks at the modification dates of tclIndex
and the three Tcl files. If any of the Tcl files is more recent than
tclIndex, or if tclIndex does not exist, then
tclmake executes the command, which updates tclIndex.
The targets given on the command line when tclmake is invoked are called the goals, since these are the targets that tclmake will try to update. If no goals are given on the command line, then tclmake will use the targets of the first rule in the makefile as its goals.
Dependencies are typically chained. For example, suppose that each Tcl file also depends on some other file, such as a source-code control file. In that case, we might have a rule like this:
%.tcl :: SCCS/s.%.tcl
exec sccs get $<
This rule says that any file with the .tcl suffix depends on a
file in the SCCS directory. (The double-colon is explained in Double-colon rules.) Suppose we try to make
tclIndex. tclmake sees that this file depends on
main.tcl. However, instead of just checking the date of
main.tcl, it also sees that main.tcl depends on
SCCS/s.main.tcl, so tclmake then checks whether
SCCS/s.main.tcl is newer than main.tcl. If it is, it
executes the sccs command, and then executes the command that
updates tclIndex. (If not, then it goes back and compares the
file dates of tclIndex and main.tcl, as before.)
A makefile (or, as I call them in the rest of this document to distinguish between makefiles for regular make and makefiles for tclmake, a "tclmakefile") thus captures arbitrarily complex dependencies between files; tclmake provides the resolution mechanism that ensures that files are updated or regenerated in the correct order.
