GNU Autotools is a build system that helps you distribute your code in a predictable and reliable way.
Build systems offer many benefits, including:

Standard and automate-able build process
hooks into packaging systems (RPM, DEB, Slackbuilds, Flatpak, Snap, and so on)
version reporting
build for various OSes
you get lots of code to handle every possible corner case, for free
with a single configuration, you can build your project as the developer, build it for packagers, and enable users to build it for themselves

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