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

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/V3_chap02.html 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/ https://pubs.opengroup.org/onlinepubs/9699919799/utilities/ Any POSIX-compliant system is required to implement the functionality described there.