diff --git a/src/lib/args.zig b/src/lib/args.zig
new file mode 100644
index 0000000..a206d61
--- /dev/null
+++ b/src/lib/args.zig
@@ -0,0 +1,16 @@
+const std = @import("std");
+const process = std.process;
+const print = std.debug.print;
+
+pub fn getFirstArg() [:0]const u8 {
+    var args = process.args();
+    defer args.deinit();
+
+    // Skip the first argument since it's the name of the program.
+    _ = args.skip();
+
+    return args.next() orelse {
+        print("Provide at least one input\n", .{});
+        process.exit(1);
+    };
+}
diff --git a/src/lib/files.zig b/src/lib/files.zig
new file mode 100644
index 0000000..5d124c0
--- /dev/null
+++ b/src/lib/files.zig
@@ -0,0 +1,13 @@
+const std = @import("std");
+const fs = std.fs;
+const File = std.fs.File;
+
+pub fn openForReading(rel_path: []const u8) !File {
+    var abs_path_buff: [fs.max_path_bytes]u8 = undefined;
+    const abs_path = try fs.realpath(rel_path, &abs_path_buff);
+    return try fs.openFileAbsolute(abs_path, File.OpenFlags{ .mode = .read_only });
+}
+
+pub fn readLine(file: File, buf: []u8) ![]u8 {
+    return try file.reader().readUntilDelimiter(buf, '\n');
+}