The rule for a target need not always produce a file, but if it does, the file for which the target is named is referred to as the target file. make treats dependencies as prerequisite targets, and updates them (if necessary) before processing its current target. The makefile entry for a target contains its name, a list of targets on which it depends, and a list of commands for building it. Each file to build, or step to perform, is called a target.
make reads the recipe, decides which steps need to be performed, and executes only those steps that are required to produce the finished module. This lets you specify a hierarchy of steps in a top-to-bottom fashion. A module can be treated as out of date if the commands used to build it have changed.īecause make does a complete dependency scan, changes to a source file are consistently propagated through any number of intermediate files or processing steps. If the module is missing, or if it is older than the dependency file, make considers it to be out of date, and issues the commands necessary to rebuild it. To determine whether a derived file is out of date with respect to its sources, make compares the modification time of the (existing) module with that of its dependency file. make only rebuilds a module if one or more of these prerequisite files, called dependency files, has changed since the module was last built.
It uses the mechanism of dependency checking to compare each module with the source or intermediate files it derives from.
#MAKEFILE VS RUNJS HOW TO#
Make allows you to write a simple, structured listing of what to build and how to build it. Although it is possible to write a script of sufficient complexity to recompile only those modules that require it, make does this job better. On the other hand, having to edit the script for each iteration can defeat the goal of consistency. On the one hand, you don't want to wait for a simple minded script to compile every single program or object module when only one of them has changed.
While it is possible to use a shell script to assure consistency in trivial cases, scripts to build software projects are often inadequate.
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