diff --git a/lib/DB.zig b/lib/DB.zig
index 9793108..d27c97c 100644
--- a/lib/DB.zig
+++ b/lib/DB.zig
@@ -9,7 +9,6 @@ const Allocator = std.mem.Allocator;
 const ArrayList = std.ArrayList;
 const AutoHashMap = std.AutoHashMap;
 const BoundedArray = std.BoundedArray;
-const ArenaAllocator = std.heap.ArenaAllocator;
 
 const Corpus = @import("Corpus.zig");
 const pad = @import("padding.zig");
@@ -149,6 +148,14 @@ pub fn fromCorpus(
     };
 }
 
+pub fn getgrBufsize(self: *const DB) usize {
+    return self.header.getgr_bufsize;
+}
+
+pub fn getpwBufsize(self: *const DB) usize {
+    return self.header.getpw_bufsize;
+}
+
 pub fn deinit(self: *DB, allocator: Allocator) void {
     allocator.destroy(self.header);
     allocator.free(self.bdz_gid);
@@ -336,7 +343,7 @@ fn getUser(self: *const DB, user: PackedUser, buf: *[]u8) error{OutOfMemory}!CUs
 }
 
 // get a CUser entry by name.
-fn getpwnam(self: *const DB, name: []const u8, buf: *[]u8) error{OutOfMemory}!?CUser {
+pub fn getpwnam(self: *const DB, name: []const u8, buf: *[]u8) error{OutOfMemory}!?CUser {
     const idx = bdz.search(self.bdz_username, name);
     // bdz may return a hash that's bigger than the number of users
     if (idx >= self.header.num_users) return null;
@@ -348,7 +355,7 @@ fn getpwnam(self: *const DB, name: []const u8, buf: *[]u8) error{OutOfMemory}!?C
 }
 
 // get a CUser entry by uid.
-fn getpwuid(self: *const DB, uid: u32, buf: *[]u8) error{OutOfMemory}!?CUser {
+pub fn getpwuid(self: *const DB, uid: u32, buf: *[]u8) error{OutOfMemory}!?CUser {
     const idx = bdz.search_u32(self.bdz_uid, uid);
     if (idx >= self.header.num_users) return null;
     const offset = self.idx_uid2user[idx];
@@ -644,7 +651,7 @@ test "getgrnam/getgrgid" {
     defer corpus.deinit();
     var db = try DB.fromCorpus(testing.allocator, &corpus);
     defer db.deinit(testing.allocator);
-    var buf = try testing.allocator.alloc(u8, db.header.getgr_bufsize);
+    var buf = try testing.allocator.alloc(u8, db.getgrBufsize());
     defer testing.allocator.free(buf);
 
     {
@@ -677,7 +684,7 @@ test "getpwnam/getpwuid" {
     defer corpus.deinit();
     var db = try DB.fromCorpus(testing.allocator, &corpus);
     defer db.deinit(testing.allocator);
-    var buf = try testing.allocator.alloc(u8, db.header.getpw_bufsize);
+    var buf = try testing.allocator.alloc(u8, db.getpwBufsize());
     defer testing.allocator.free(buf);
 
     {
diff --git a/lib/File.zig b/lib/File.zig
index 35d2765..a3ac21d 100644
--- a/lib/File.zig
+++ b/lib/File.zig
@@ -1,6 +1,9 @@
 const std = @import("std");
 const os = std.os;
+const fs = std.fs;
+const Allocator = std.mem.Allocator;
 
+const Corpus = @import("Corpus.zig");
 const DB = @import("DB.zig");
 const InvalidHeader = @import("header.zig").Invalid;
 
@@ -13,12 +16,10 @@ pub const Error = os.OpenError || os.FStatError || os.MMapError || InvalidHeader
 pub fn open(fname: []const u8) Error!File {
     const fd = try os.open(fname, os.O.RDONLY, 0);
     var fd_open = true;
-    errdefer {
-        if (fd_open) os.close(fd);
-    }
+    errdefer if (fd_open) os.close(fd);
 
     const st = try os.fstat(fd);
-    const size = @intCast(u64, st.size);
+    const size = @intCast(usize, st.size);
     const ptr = try os.mmap(null, size, os.PROT.READ, os.MAP.SHARED, fd, 0);
     errdefer os.munmap(ptr);
 
@@ -33,3 +34,38 @@ pub fn close(self: *File) void {
     os.munmap(self.ptr);
     self.* = undefined;
 }
+
+const testing = std.testing;
+
+pub const TestFile = struct {
+    dir: testing.TmpDir,
+    path: [:0]const u8,
+
+    pub fn init(allocator: Allocator) !TestFile {
+        var corpus = try Corpus.testCorpus(allocator);
+        defer corpus.deinit();
+
+        var db = try DB.fromCorpus(allocator, &corpus);
+        defer db.deinit(allocator);
+
+        var tmp = testing.tmpDir(.{});
+        errdefer tmp.cleanup();
+
+        const mode = os.O.RDWR | os.O.CREAT | os.O.EXCL;
+        const fd = try os.openat(tmp.dir.fd, "db.turbo", mode, 0o666);
+        defer os.close(fd);
+
+        _ = try os.writev(fd, db.iov().constSlice());
+        const dir_path = try tmp.getFullPath(allocator);
+        defer allocator.free(dir_path);
+
+        const full = &[_][]const u8{ dir_path, "db.turbo\x00" };
+        var result = try fs.path.join(allocator, full);
+        return TestFile{ .dir = tmp, .path = result[0 .. result.len - 1 :0] };
+    }
+
+    pub fn deinit(self: *TestFile, allocator: Allocator) void {
+        self.dir.cleanup();
+        allocator.free(self.path);
+    }
+};
diff --git a/lib/libnss.zig b/lib/libnss.zig
index 53d25b9..4cb01d1 100644
--- a/lib/libnss.zig
+++ b/lib/libnss.zig
@@ -2,6 +2,7 @@ const std = @import("std");
 const os = std.os;
 const fmt = std.fmt;
 const mem = std.mem;
+const process = std.process;
 
 const DB = @import("DB.zig");
 const File = @import("File.zig");
@@ -11,10 +12,16 @@ const CUser = @import("User.zig").CUser;
 const PackedUser = @import("PackedUser.zig");
 
 const c = @cImport({
-    @cInclude("stdlib.h");
     @cInclude("nss.h");
 });
 
+const TURBONSS_DB = "DB";
+const TURBONSS_VERBOSE = "TURBONSS_VERBOSE";
+const TURBONSS_OMIT_MEMBERS = "TURBONSS_OMIT_MEMBERS";
+
+extern fn putenv(name: [*:0]const u8, value: [*:0]const u8, overwrite: c_int) c_int;
+extern fn getenv(name: [*:0]const u8) ?[*:0]const u8;
+
 export const turbonss_default_path: [:0]const u8 = "/etc/turbonss/db.turbo";
 
 // State is a type of the global variable holding the process state:
@@ -24,7 +31,29 @@ const State = struct {
     getpwent_iterator: ?PackedUser.Iterator,
     getgrent_iterator: ?PackedGroup.Iterator,
     omit_members: bool,
-    err_msg: [1024]u8,
+    verbose: bool = false,
+
+    fn debug(self: *const State, comptime format: []const u8, args: anytype) void {
+        self.log(.debug, format, args);
+    }
+    fn info(self: *const State, comptime format: []const u8, args: anytype) void {
+        self.log(.info, format, args);
+    }
+    fn err(self: *const State, comptime format: []const u8, args: anytype) void {
+        self.log(.err, format, args);
+    }
+    fn log(
+        self: *const State,
+        comptime level: std.log.Level,
+        comptime format: []const u8,
+        args: anytype,
+    ) void {
+        if (!self.verbose) return;
+        const stderr = std.io.getStdErr().writer();
+        std.debug.getStderrMutex().lock();
+        defer std.debug.getStderrMutex().unlock();
+        stderr.print("[" ++ level.asText() ++ "] " ++ format ++ "\n", args) catch return;
+    }
 };
 
 // state is initialized on library startup.
@@ -32,14 +61,29 @@ var state: State = undefined;
 
 // constructor
 export fn _turbo_init() void {
-    const fname = os.getenvZ("TURBONSS_DB") orelse turbonss_default_path[0..];
+    //if (os.getenvZ(TURBONSS_VERBOSE)) |env|
+    //    state.verbose = mem.eql(u8, env, "1");
+
+    if (getenv(TURBONSS_VERBOSE)) |env| {
+        const envZ = mem.sliceTo(env, 0);
+        state.verbose = mem.eql(u8, envZ, "1");
+    }
+
+    //std.debug.print("TURBONSS_VERBOSE: {s}\n", .{os.getenv(TURBONSS_VERBOSE)});
+    std.debug.print("TURBONSS_VERBOSE: {s}\n", .{getenv(TURBONSS_VERBOSE)});
+    std.debug.print("verbose: {any}\n", .{state.verbose});
+
+    const fname = os.getenvZ(TURBONSS_DB) orelse turbonss_default_path[0..];
+    state.debug("opening {s}", .{fname});
     state.file = File.open(fname) catch |err| {
-        _ = fmt.bufPrint(&state.err_msg, "open {s}: {s}", .{ fname, @errorName(err) }) catch return;
+        state.err("open {s}: {s}", .{ fname, @errorName(err) });
         return;
     };
+    state.debug("turbonss database opened", .{});
 
-    const omit_members_env = os.getenvZ("TURBONSS_OMIT_MEMBERS") orelse "auto";
+    const omit_members_env = os.getenvZ(TURBONSS_OMIT_MEMBERS) orelse "auto";
     state.omit_members = shouldOmitMembers(omit_members_env, os.argv);
+    state.debug("omitting members from getgr* calls: {any}\n", .{state.omit_members});
 
     return;
 }
@@ -65,10 +109,43 @@ export fn _nss_turbo_getpwuid_r(
     len: usize,
     errnop: *c_int,
 ) c.enum_nss_status {
-    _ = uid;
-    _ = res;
-    _ = buf;
-    _ = len;
-    _ = errnop;
-    return 0;
+    if (state.file == null) {
+        errnop.* = @enumToInt(os.E.AGAIN);
+        return c.NSS_STATUS_UNAVAIL;
+    }
+    const cuser = state.file.?.db.getpwuid(uid, &buf[0..len]) catch |err| switch (err) {
+        error.OutOfMemory => {
+            errnop.* = @enumToInt(os.E.RANGE);
+            return c.NSS_STATUS_TRYAGAIN;
+        },
+    };
+
+    if (cuser == null) {
+        errnop.* = @enumToInt(os.E.NOENT);
+        return c.NSS_STATUS_NOTFOUND;
+    }
+    res.* = cuser.?;
+
+    return c.NSS_STATUS_SUCCESS;
+}
+
+const testing = std.testing;
+
+test "nss_turbo_getpwuid_r" {
+    var tf = try File.TestFile.init(testing.allocator);
+    defer tf.deinit(testing.allocator);
+
+    var env = try process.getEnvMap(testing.allocator);
+    defer env.deinit();
+
+    try testing.expectEqual(putenv(TURBONSS_VERBOSE, "1", 1), 0);
+    try testing.expectEqual(putenv(TURBONSS_DB, tf.path, 1), 0);
+    _turbo_init();
+    try testing.expect(state.file != null);
+
+    var buf = try testing.allocator.alloc(u8, state.file.?.db.getpwBufsize());
+    var user: CUser = undefined;
+    var errno: c_int = undefined;
+    const ret = _nss_turbo_getpwuid_r(128, &user, buf.ptr, buf.len, &errno);
+    try testing.expectEqual(ret, c.NSS_STATUS_SUCCESS);
 }