diff --git a/examples/ex-06.copy.zig b/examples/ex-06.copy.zig
index 983fcfb..e859054 100644
--- a/examples/ex-06.copy.zig
+++ b/examples/ex-06.copy.zig
@@ -6,6 +6,7 @@ const TokenIter = zargs.TokenIter;
 const ztype = @import("ztype");
 const String = ztype.String;
 const Open = ztype.Open;
+const Read = ztype.Read;
 
 pub fn main() !void {
     const cmd = Command.new("copy").alias("cp")
@@ -14,7 +15,7 @@ pub fn main() !void {
         .homepage("https://github.com/kioz-wang/zargs")
         .arg(Arg.opt("verbose", bool).short('v').long("verbose").help("Show detail"))
         .arg(Arg.optArg("max", usize).long("max").help("Max byte to copy").default(32 << 10))
-        .arg(Arg.posArg("source", Open(.file, .{})))
+        .arg(Arg.posArg("source", Read()))
         .arg(Arg.posArg("target", Open(.fileCreate, .{})))
         .config(.{ .style = .classic });
 
@@ -28,11 +29,11 @@ pub fn main() !void {
     if (args.verbose) {
         std.debug.print("Try copy {s} to {s} with max 0x{x} bytes\n", .{ args.source.s, args.target.s, args.max });
     }
-    const content = try args.source.v.reader().any().readAllAlloc(allocator, args.max);
-    defer allocator.free(content);
-    try args.target.v.writer().any().writeAll(content);
+    // const content = try args.source.v.reader().any().readAllAlloc(allocator, args.max);
+    // defer allocator.free(content);
+    try args.target.v.writer().any().writeAll(args.source.v);
     if (args.verbose) {
-        std.debug.print("Done with 0x{x} bytes\n", .{content.len});
+        std.debug.print("Done with 0x{x} bytes\n", .{args.source.v.len});
     }
 }
 
diff --git a/src/type/base.zig b/src/type/base.zig
new file mode 100644
index 0000000..9920e47
--- /dev/null
+++ b/src/type/base.zig
@@ -0,0 +1,2 @@
+pub const String = []const u8;
+pub const LiteralString = [:0]const u8;
diff --git a/src/type/checker.zig b/src/type/checker.zig
index a3e21c4..695c4d3 100644
--- a/src/type/checker.zig
+++ b/src/type/checker.zig
@@ -1,8 +1,8 @@
 const std = @import("std");
 const testing = std.testing;
 
-const String = []const u8;
-const LiteralString = [:0]const u8;
+const String = @import("base.zig").String;
+const LiteralString = @import("base.zig").LiteralString;
 
 pub fn isBase(T: type) bool {
     if (T == String) return true;
diff --git a/src/type/open.zig b/src/type/open.zig
index cbe8d6a..76d5919 100644
--- a/src/type/open.zig
+++ b/src/type/open.zig
@@ -1,7 +1,7 @@
 const std = @import("std");
 
-const String = []const u8;
-const LiteralString = [:0]const u8;
+const String = @import("base.zig").String;
+const LiteralString = @import("base.zig").LiteralString;
 
 const OpenType = enum { file, fileCreate, dir, dirCreate };
 fn OpenFlags(openType: OpenType) type {
@@ -50,11 +50,11 @@ fn OpenFn(openType: OpenType, lazy: bool, flags: OpenFlags(openType)) type {
                 },
                 else => {},
             }
-            if (!lazy) _ = self.unlazy() catch return null;
+            if (!lazy) _ = self.unlazy(a_maybe) catch return null;
 
             return self;
         }
-        pub fn unlazy(self: *Self) !OpenValue(openType) {
+        pub fn unlazy(self: *Self, _: ?std.mem.Allocator) !OpenValue(openType) {
             if (!self.@".is_inited") {
                 self.v = switch (openType) {
                     .file => try std.fs.cwd().openFile(self.s, flags),
diff --git a/src/type/read.zig b/src/type/read.zig
new file mode 100644
index 0000000..92d80b4
--- /dev/null
+++ b/src/type/read.zig
@@ -0,0 +1,53 @@
+const std = @import("std");
+
+const String = @import("base.zig").String;
+const LiteralString = @import("base.zig").LiteralString;
+
+fn ReadFn(lazy: bool) type {
+    return struct {
+        const Self = @This();
+        v: String = undefined,
+        s: String = undefined,
+        @".is_inited": bool = false,
+        pub fn parse(s: String, a_maybe: ?std.mem.Allocator) ?Self {
+            var self: Self = .{};
+
+            self.s = blk: {
+                const s_alloc = a_maybe.?.alloc(u8, s.len) catch return null;
+                @memcpy(s_alloc, s);
+                break :blk s_alloc;
+            };
+
+            if (!lazy) _ = self.unlazy(a_maybe) catch return null;
+
+            return self;
+        }
+        pub fn unlazy(self: *Self, a_maybe: ?std.mem.Allocator) !String {
+            if (!self.@".is_inited") {
+                var fp = if (std.mem.eql(u8, self.s, "-")) std.io.getStdIn() else try std.fs.cwd().openFile(self.s, .{});
+                defer fp.close();
+                self.v = try fp.readToEndAlloc(a_maybe.?, 4 << 10);
+                self.@".is_inited" = true;
+            }
+            return self.v;
+        }
+        pub fn destroy(self: *Self, a_maybe: ?std.mem.Allocator) void {
+            if (self.@".is_inited") a_maybe.?.free(self.v);
+            a_maybe.?.free(self.s);
+        }
+        pub fn format(self: Self, comptime _: []const u8, _: std.fmt.FormatOptions, writer: anytype) @TypeOf(writer).Error!void {
+            try writer.print("Read({s})", .{self.s});
+        }
+    };
+}
+
+pub const Read = struct {
+    pub fn f() type {
+        return ReadFn(false);
+    }
+}.f;
+pub const ReadLazy = struct {
+    pub fn f() type {
+        return ReadFn(true);
+    }
+}.f;
diff --git a/src/type/root.zig b/src/type/root.zig
index 81b2f04..cef47df 100644
--- a/src/type/root.zig
+++ b/src/type/root.zig
@@ -8,8 +8,9 @@
 //! const ... = ztype.zzz;
 //! ```
 
-pub const String = []const u8;
-pub const LiteralString = [:0]const u8;
+const base = @import("base.zig");
+pub const String = base.String;
+pub const LiteralString = base.LiteralString;
 
 pub const checker = @import("checker.zig");
 
@@ -17,6 +18,10 @@ const open = @import("open.zig");
 pub const Open = open.Open;
 pub const OpenLazy = open.OpenLazy;
 
+const read = @import("read.zig");
+pub const Read = read.Read;
+pub const ReadLazy = read.ReadLazy;
+
 test {
     @import("std").testing.refAllDecls(@This());
 }