Curriculum Basics Hello and output exercise 5 · fill-word

Hello and output

Fill the missing keyword. The writeStreamingAll call returns an error union — leaving the return value uncaught is a compile error. The keyword you need propagates the error up to the enclosing function's !void return.

TypeScript reference

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About this theme

Two reflexes Zig wants you to internalise on day one.

Imports use a builtin, not a keyword. const std = @import("std"); binds the standard library to a name. There's no import keyword and no use keyword. @import is one of dozens of compiler builtins (everything starting with @) — you don't need the full list, just the muscle memory.
main takes an init: std.process.Init. Zig's entry point used to be parameterless; modern Zig threads I/O capabilities (and soon, allocator handles) through an Init value the runtime constructs for you. You hand init.io to anything that touches files / stdout / stderr. The signature is pub fn main(init: std.process.Init) !void — the !void says "may fail with an error".

Writing to stdout therefore reads as: get the stdout File handle, ask it to stream a slice of bytes through init.io.

try std.Io.File.stdout().writeStreamingAll(init.io, "hello\n");

try propagates the error if the write fails; !void in the main signature is what allows it. We'll come back to error unions properly in the errors module.