Lexing portion is complete.

Tested manually but not in an automated fashion.

src/main.zig

@@ -0,0 +1,63 @@
+const std = @import("std");
+
+const scanner = @import("scanner.zig");
+const err = @import("error.zig");
+
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
+    defer _ = gpa.deinit();
+    const allocator = gpa.allocator();
+
+    const args = try std.process.argsAlloc(allocator);
+    defer std.process.argsFree(allocator, args);
+
+    if (args.len > 2) {
+        std.debug.print("Usage: zloxi [script].", .{});
+        std.process.exit(64);
+    } else if (args.len == 2) {
+        try runFile(allocator, args[1]);
+        if (err.hasError) {
+            std.process.exit(65);
+        }
+    } else {
+        try runPrompt(allocator);
+    }
+}
+
+fn runFile(alloc: std.mem.Allocator, file_name: []u8) !void {
+    var bytes = try std.fs.cwd().readFileAlloc(alloc, file_name, 1_000_000);
+    defer alloc.free(bytes);
+    try run(alloc, bytes);
+}
+
+fn runPrompt(alloc: std.mem.Allocator) !void {
+    const stdout_file = std.io.getStdOut().writer();
+    const stdin_file = std.io.getStdIn().reader();
+    var bw = std.io.bufferedWriter(stdout_file);
+    const stdout = bw.writer();
+
+    while (true) {
+        try stdout.print("> ", .{});
+        try bw.flush();
+
+        const line = try stdin_file.readUntilDelimiterOrEofAlloc(alloc, '\n', 1000);
+        if (line == null) {
+            try stdout.print("\n", .{});
+            break;
+        }
+        defer alloc.free(line.?);
+        try run(alloc, line.?);
+        err.hasError = false;
+    }
+
+    try bw.flush(); // don't forget to flush!
+}
+
+fn run(allocator: std.mem.Allocator, bytes: []u8) !void {
+    var scan = scanner.Scanner.init(allocator, bytes);
+    defer scan.deinit();
+    std.debug.print("{any}\n", .{scan.scanTokens()});
+}
+
+// Error reporting
+// TODO: Move to a separate file.