> 1) GNU extensions aren't always well thought out or standardized. Assuming everywhere is a current GNU userland will break frequently on multiple non-Linux OS's - look up trying to use `awk` on MacOS, which has BSD derived version.
Even Linux isn't as consistent as some would have you believe. I regularly find that builds or application breaks because Red Hat is different from Ubuntu. And then, busybox is different from RHEL and Ubuntu. Also, busybox is different from older version of busybox.
I run into this often enough because customer runs stuff on RHEL while my company uses Ubuntu for development. And I happen to be working on an application that runs on different boards with different versions of busybox, as well as on mainstream x86-64 distros..
Even Linux isn't as consistent as some would have you believe. I regularly find that builds or application breaks because Red Hat is different from Ubuntu. And then, busybox is different from RHEL and Ubuntu. Also, busybox is different from older version of busybox.
I run into this often enough because customer runs stuff on RHEL while my company uses Ubuntu for development. And I happen to be working on an application that runs on different boards with different versions of busybox, as well as on mainstream x86-64 distros..