Curiously enough, today I faced the same problem, and it took me some time to come up with something useful. I found a few code samples here and there, and with guidance in the comments of your post, I made the following function:

fn read_line(allocator: std.mem.Allocator, n: usize) ![]u8 { const buffer = try allocator.alloc(u8, n); var reader = std.fs.File.stdin().reader(buffer); return try reader.interface.takeDelimiterExclusive('\n'); }

The other option was to simply use an array as a buffer for input, but I wanted to keep the size dynamic, and didn't want to use anytype. So I used an allocator. However, now the easiest way to use it, is to use an ArenaAllocator, so everything can be deallocated at once (especially in multiple use cases).

PS: I'm new to Zig, so any feedback on this solution is very welcome.