Question

I found such an example of scanf in C book (this time not K&R):

scanf(" %[-' A-Za-z]s",&variable);

Can anybody provide me with information what does it accept?
I have not found any info about using ‘a’ or ‘z’ as conversion characters

Answer 1

From the standard (C11, §7.19.6.2/12):

] Matches a nonempty sequence of characters from a set of expected characters

That means that your format expects a run of of the characters -, space, A, …, Z, a, …, z.

The [ conversion specifier has provisions for two special characters: %[^... inverts the matching set, and a hyphen (-) between two characters indicates a range, as is used in your A-Z and a-z.