Full example

const std = @import("std");

pub fn main() !void {
    // If this program is run without stdout attached, exit with an error.
    const stdout_file = try std.io.getStdOut();
    // If this program encounters pipe failure when printing to stdout, exit
    // with an error.
    try stdout_file.write("Hello, world!\n");
}

const warn = @import("std").debug.warn;

pub fn main() void {
    warn("Hello, world!\n");
}

const assert = @import("std").debug.assert;

test "comments" {
    // Comments in Zig start with "//" and end at the next LF byte (end of line).
    // The below line is a comment, and won't be executed.

    //assert(false);

    const x = true;  // another comment
    assert(x);
}

/// A structure for storing a timestamp, with nanosecond precision (this is a
/// multiline doc comment).
const Timestamp = struct {
    /// The number of seconds since the epoch (this is also a doc comment).
    seconds: i64,  // signed so we can represent pre-1970 (not a doc comment)
    /// The number of nanoseconds past the second (doc comment again).
    nanos: u32,

    /// Returns a `Timestamp` struct representing the Unix epoch; that is, the
    /// moment of 1970 Jan 1 00:00:00 UTC (this is a doc comment too).
    pub fn unixEpoch() Timestamp {
        return Timestamp{
            .seconds = 0,
            .nanos = 0,
        };
    }
};