pkgsrc is a framework for building third-party software on UNIX-like systems. It currently contains over 17000 packages.
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Pro Offering tooling for backporting fixes
Backporting fixes can be done by cherry-picking updates from a newer branch (pkgsrc is released every 3 months) and creating a package. Sometimes bugs need to be fixed for production and there is neither a fix in newer pkgsrc nor the softwares upstream. So pkgsrc has tools like pkgdiff, mkpatches, etc. that help with developing patches and building binary packages from that. A bit of documentation about that process can be found here.
Pro Both binary packages and source build possible
Fast software installation is possible by using binary packages. It's also easy to build from source which allows for different compile-time options (like different UI backends) as well as gaining access to pre-release versions of software in certain cases.
Pro pkgin is an apt-like tools for installing binaries from pkgsrc
pkgin aims to be a tool similar to apt/yum for managing pkgsrc binaries by relying on pkg_summary for installing, removing and upgrading packages and dependencies, using a remote repo.
Pro Adapted for use on over a dozen different operating systems
Has been adopted to be used on several Unix-like operating systems and Windows. It's also the default package manager of DragonflyBSD and of the (now discounted) Bluewall Linux distro.
Con Relatively complicated setup and installation
Installing and setting pkgsrc up is a bit more complicated than in other package managers where it often consists in running a single script.