- #How to write a makefile for multiple files update
- #How to write a makefile for multiple files manual
- #How to write a makefile for multiple files archive
- #How to write a makefile for multiple files code
You can approximate URL dependencies by checking the Last-Modified header via curl -I. Otherwise Make will crash with a cryptic error.) If it worked, you should see a downloaded counties.zip in the directory. (Note: use tabs rather than spaces to indent the commands in your makefile.
#How to write a makefile for multiple files code
Put this code in a file called Makefile, and then run make from the same directory.
#How to write a makefile for multiple files archive
Here’s the rule to download the zip archive from the Census Bureau: In Make parlance, source files are referred to as prerequisites, while target files are simply targets. These terms generalize: a source file can itself be a generated file, in turn dependent on other source files there can be multiple source files, or zero source files and a command can be a sequence of commands or a complex script that you invoke. Here targetfile is the file you want to generate, sourcefile is the file it depends on (is derived from), and command is something you run on the terminal to generate the target file. Fortunately, you can ignore most of this, and start with explicit rules of the following form:
#How to write a makefile for multiple files manual
The ugly side of Make is its syntax and complexity the full manual is a whopping 183 pages. A well-designed makefile allows you to iterate quickly while keeping generated files consistent and up-to-date. Capturing dependencies also begets efficiency: you can remake generated files with only minimal effort when anything changes. Unlike a linear script, a dependency graph is flexible and modular for example, you can augment the makefile to derive multiple shapefiles from the same zip archive without repeated downloads. This way of thinking can be uncomfortable at first, but it has advantages. So to express your workflow in language that Make understands, consider instead the dependency graph: For example, the shapefile depends on the zip archive because you must download the archive before you can extract the shapefile (obviously). In a mildly mind-bending maneuver, Make encourages you to express your workflow backwards as dependencies between files, rather than forwards as a sequential recipe.
Say you’re building a choropleth map of unemployment and you need a TopoJSON file of U.S. When generated files are missing, or when files they depend on have changed, needed files are re-made using a sequence of commands you specify. The core concept is that generated files depend on other files.
It doesn’t fundamentally change how you do something, but it encourages to you record each step in the process, enabling you (and your coworkers) to reproduce the entire process later. The beauty of Make is that it’s simply a rigorous way of recording what you’re already doing. I could have simply typed make in the terminal and be done! But I was left thinking how much easier it could have been had I simply recorded the process the first time as a makefile. Shamefully, I hadn’t documented the data-transformation process, and it’s painfully easy to forget details over six months: I had a mess of CSV and GeoJSON data files, but not the exact source URL from the NCDC I was temporarily confused as to the right Palmer drought metric (Drought Severity Index or Z Index?) and the corresponding categorical thresholds finally, I had to resurrect the code to calculate drought coverage area.ĭespite these challenges, we republished the updated graphic without too much delay. The article was already on the homepage, so the clock was ticking to republish with new data as soon as possible.
#How to write a makefile for multiple files update
To illustrate with a recent example: yesterday Kevin and I needed to update a six-month old graphic on drought to accompany a new article on thin snowpack in the West. To clarify, this post isn’t just about GNU Make it’s about the benefits of capturing workflows via a file-based dependency-tracking build system, including modern alternatives such as Rake and Waf. Makefiles are machine-readable documentation that make your workflow reproducible. You may think of Make as merely a tool for building large binaries or libraries (and it is, almost to a fault), but it’s much more than that. Why Use Make FebruMike Bostock Why Use Make