A minimal build system using Bourne sh http://akkartik.name/post/four-repos
Kartik K. Agaram 749ae780a8 don't make readers think of Prolog the language | 7 years ago | |
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Readme.md | 7 years ago | |
build | 7 years ago | |
x.c | 7 years ago |
Build systems have a tendency to create languages, and their languages have a way of growing increasingly complex over time.
They work well once you get them working in your environment, but if they don't work out of the box for some reason, they can be daunting for your users to debug.
A common source of build errors is incompatibilities between build languages
on different platforms. GNU make
isn't the same as BSD make
. autotools
can autogenerate Makefile
s for endless obsolete flavors of Unix, but it
only serves to hinder you on the platform you're on right now.
cmake
can autogenerate build files for m build tools in n platforms,
which means it needs to understand mXn mappings between DSLs.
An alternative approach is to sidestep existing tools (i.e. make
) rather
than build atop them. This repo illustrates a way to manage a project using
just plain Bourne sh
, available on all Unix systems for 30 years. No place
for incompatibilities to rear their heads!
Say you have a command to run:
cc input1.c input2.c -o output
To only do this work when necessary, wrap this command in an older_than
block:
older_than output input1.c input2.c && {
cc input1 input2 -o output
}
If the output is newer than all inputs, nothing happens.
If any of the inputs is newer than the output, the command runs and updates the output.
A sequence of such blocks can mimic any makefile
, and the extra verbosity
can help someone debug your project if it doesn't work for them. Every command
is explicit, as is the order to try them in.
To see older_than
at work and a more complete example of its use, try
running the build
script in this repo.
$ ./build
updating a.out
$ ./a.out
hello, world!
$ ./build
# no change to a.out
The build
script is easy to repurpose to your needs. The older_than
function in it is 16 lines of code.