Why does a ‘.’ work in chown

chowncoreutilsgnuhistory

Why does GNU chown user.group work? The docs say nothing of the syntax being supported. Is there a juicy story behind it?

Best Answer

info chown is clear on that:

Some older scripts may still use `.' in place of the `:' separator.
POSIX 1003.1-2001 (*note Standards conformance::) does not require
support for that, but for backward compatibility GNU `chown' supports
`.' so long as no ambiguity results. New scripts should avoid the use
of `.' because it is not portable, and because it has undesirable
results if the entire OWNER`.'GROUP happens to identify a user whose
name contains `.'.

In case of GNU programs it's often worth checking not only man but also info pages because GNU folks abhor man pages (from man tar).

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