[chasil]

You might find it interesting to know exactly what is (and is not) in the POSIX shell. The description of the colon : operator is there.

https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V...

Most of the familiar userland utilities are at that website, accessible as a (somewhat crude) Apache index:

https://pubs.opengroup.org/onlinepubs/9699919799/utilities/

Any POSIX-compliant system is required to implement the functionality described there.