diff --git a/libc/src/unistd/linux/getuid.cpp b/libc/src/unistd/linux/getuid.cpp
@@ -0,0 +1,22 @@
+//===-- Linux implementation of getuid ------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/unistd/getuid.h"
+
+#include "src/__support/OSUtil/syscall.h" // For internal syscall function.
+#include "src/__support/common.h"
+
+#include <sys/syscall.h> // For syscall numbers.
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(uid_t, getuid, ()) {
+  return __llvm_libc::syscall(SYS_getuid);
+}
+
+} // namespace __llvm_libc
diff --git a/libc/test/src/unistd/CMakeLists.txt b/libc/test/src/unistd/CMakeLists.txt
@@ -321,3 +321,43 @@ add_libc_unittest(
     libc.src.unistd.close
     libc.src.unistd.unlinkat
 )
+
+add_libc_unittest(
+  getpid_test
+  SUITE
+    libc_unistd_unittests
+  SRCS
+    getpid_test.cpp
+  DEPENDS
+    libc.src.unistd.getpid
+)
+
+add_libc_unittest(
+  getppid_test
+  SUITE
+    libc_unistd_unittests
+  SRCS
+    getppid_test.cpp
+  DEPENDS
+    libc.src.unistd.getppid
+)
+
+add_libc_unittest(
+  getuid_test
+  SUITE
+    libc_unistd_unittests
+  SRCS
+    getuid_test.cpp
+  DEPENDS
+    libc.src.unistd.getuid
+)
+
+add_libc_unittest(
+  geteuid_test
+  SUITE
+    libc_unistd_unittests
+  SRCS
+    geteuid_test.cpp
+  DEPENDS
+    libc.src.unistd.geteuid
+)
diff --git a/libc/test/src/unistd/geteuid_test.cpp b/libc/test/src/unistd/geteuid_test.cpp
@@ -0,0 +1,15 @@
+//===-- Unittests for geteuid ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/unistd/geteuid.h"
+#include "utils/UnitTest/Test.h"
+
+TEST(LlvmLibcGetEuidTest, SmokeTest) {
+  // geteuid always succeeds. So, we just call it as a smoke test.
+  __llvm_libc::geteuid();
+}
diff --git a/libc/test/src/unistd/getpid_test.cpp b/libc/test/src/unistd/getpid_test.cpp
@@ -0,0 +1,15 @@
+//===-- Unittests for getpid ----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/unistd/getpid.h"
+#include "utils/UnitTest/Test.h"
+
+TEST(LlvmLibcGetPidTest, SmokeTest) {
+  // getpid always succeeds. So, we just call it as a smoke test.
+  __llvm_libc::getpid();
+}
diff --git a/libc/test/src/unistd/getppid_test.cpp b/libc/test/src/unistd/getppid_test.cpp
@@ -0,0 +1,15 @@
+//===-- Unittests for getppid ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/unistd/getppid.h"
+#include "utils/UnitTest/Test.h"
+
+TEST(LlvmLibcGetPpidTest, SmokeTest) {
+  // getppid always succeeds. So, we just call it as a smoke test.
+  __llvm_libc::getppid();
+}
diff --git a/libc/test/src/unistd/getuid_test.cpp b/libc/test/src/unistd/getuid_test.cpp
@@ -0,0 +1,15 @@
+//===-- Unittests for getuid ----------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/unistd/getuid.h"
+#include "utils/UnitTest/Test.h"
+
+TEST(LlvmLibcGetUidTest, SmokeTest) {
+  // getuid always succeeds. So, we just call it as a smoke test.
+  __llvm_libc::getuid();
+}