diff --git a/libc/config/linux/x86_64/headers.txt b/libc/config/linux/x86_64/headers.txt
--- a/libc/config/linux/x86_64/headers.txt
+++ b/libc/config/linux/x86_64/headers.txt
@@ -10,6 +10,7 @@
     libc.include.pthread
     libc.include.sched
     libc.include.signal
+    libc.include.search
     libc.include.spawn
     libc.include.setjmp
     libc.include.stdio
diff --git a/libc/include/CMakeLists.txt b/libc/include/CMakeLists.txt
--- a/libc/include/CMakeLists.txt
+++ b/libc/include/CMakeLists.txt
@@ -241,6 +241,18 @@
     .llvm-libc-types.posix_spawn_file_actions_t
 )
 
+add_gen_header(
+  search
+  DEF_FILE search.h.def
+  GEN_HDR search.h
+  DEPENDS
+    .llvm_libc_common_h
+    .llvm-libc-types.action
+    .llvm-libc-types.struct_hsearch_data
+    .llvm-libc-types.entry
+    .llvm-libc-types.size_t
+)
+
 # TODO: Not all platforms will have a include/sys directory. Add the sys
 # directory and the targets for sys/*.h files conditional to the OS requiring
 # them.
diff --git a/libc/include/llvm-libc-types/CMakeLists.txt b/libc/include/llvm-libc-types/CMakeLists.txt
--- a/libc/include/llvm-libc-types/CMakeLists.txt
+++ b/libc/include/llvm-libc-types/CMakeLists.txt
@@ -84,3 +84,6 @@
 add_header(tcflag_t HDR tcflag_t.h)
 add_header(struct_termios HDR struct_termios.h DEPENDS .cc_t .speed_t .tcflag_t)
 add_header(__getoptargv_t HDR __getoptargv_t.h)
+add_header(action HDR action.h)
+add_header(entry HDR entry.h)
+add_header(struct_hsearch_data HDR struct_hsearch_data.h)
diff --git a/libc/include/llvm-libc-types/action.h b/libc/include/llvm-libc-types/action.h
new file mode 100644
--- /dev/null
+++ b/libc/include/llvm-libc-types/action.h
@@ -0,0 +1,14 @@
+//===-- Definition of type enum ACTION ------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __LLVM_LIBC_TYPES_ENUM_ACTION_H__
+#define __LLVM_LIBC_TYPES_ENUM_ACTION_H__
+
+typedef enum { FIND, ENTER } ACTION;
+
+#endif // __LLVM_LIBC_TYPES_ENUM_ACTION_H__
diff --git a/libc/include/llvm-libc-types/entry.h b/libc/include/llvm-libc-types/entry.h
new file mode 100644
--- /dev/null
+++ b/libc/include/llvm-libc-types/entry.h
@@ -0,0 +1,17 @@
+//===-- Definition of type struct ENTRY -----------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __LLVM_LIBC_TYPES_STRUCT_ENTRY_H__
+#define __LLVM_LIBC_TYPES_STRUCT_ENTRY_H__
+
+typedef struct {
+  char *key;
+  void *data;
+} ENTRY;
+
+#endif // __LLVM_LIBC_TYPES_STRUCT_ENTRY_H__
diff --git a/libc/include/llvm-libc-types/struct_hsearch_data.h b/libc/include/llvm-libc-types/struct_hsearch_data.h
new file mode 100644
--- /dev/null
+++ b/libc/include/llvm-libc-types/struct_hsearch_data.h
@@ -0,0 +1,17 @@
+//===-- Definition of type struct hsearch_data ----------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef __LLVM_LIBC_TYPES_STRUCT_HSEARCH_DATA_H__
+#define __LLVM_LIBC_TYPES_STRUCT_HSEARCH_DATA_H__
+
+struct hsearch_data {
+  void *__opaque;
+  unsigned int __unused[2];
+};
+
+#endif // __LLVM_LIBC_TYPES_STRUCT_HSEARCH_DATA_H__
diff --git a/libc/include/search.h.def b/libc/include/search.h.def
new file mode 100644
--- /dev/null
+++ b/libc/include/search.h.def
@@ -0,0 +1,20 @@
+//===-- POSIX header search.h ---------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SEARCH_H
+#define LLVM_LIBC_SEARCH_H
+
+#include <__llvm-libc-common.h>
+#include <llvm-libc-types/action.h>
+#include <llvm-libc-types/entry.h>
+#include <llvm-libc-types/size_t.h>
+#include <llvm-libc-types/struct_hsearch_data.h>
+
+%%public_api()
+
+#endif // LLVM_LIBC_SEARCH_H
diff --git a/libc/spec/posix.td b/libc/spec/posix.td
--- a/libc/spec/posix.td
+++ b/libc/spec/posix.td
@@ -1008,6 +1008,71 @@
     ]
   >;
 
+  NamedType StructHsearchDataName = NamedType<"struct hsearch_data">;
+  PtrType StructHsearchDataNamePtr = PtrType<StructHsearchDataName>;
+  NamedType ActionType = NamedType<"ACTION">;
+  NamedType EntryType = NamedType<"ENTRY">;
+  PtrType EntryTypePtr = PtrType<EntryType>;
+  PtrType EntryTypePtrPtr = PtrType<EntryTypePtr>;
+
+  HeaderSpec Search = HeaderSpec<
+    "search.h",
+    [], // Macros
+    [
+        StructHsearchDataName,
+        ActionType,
+        EntryType
+    ], // Types
+    [], // Enumerations
+    [
+        FunctionSpec<
+            "hcreate",
+            RetValSpec<IntType>,
+            [
+                ArgSpec<SizeTType>
+            ]
+        >,
+        FunctionSpec<
+            "hcreate_r",
+            RetValSpec<IntType>,
+            [  
+                ArgSpec<SizeTType>, 
+                ArgSpec<StructHsearchDataNamePtr>
+            ]
+        >,
+        FunctionSpec<
+            "hdestroy",
+            RetValSpec<VoidType>,
+            [] // Args
+        >,
+        FunctionSpec<
+            "hdestroy_r",
+            RetValSpec<VoidType>,
+            [
+                ArgSpec<StructHsearchDataNamePtr>
+            ]
+        >,
+        FunctionSpec<
+            "hsearch",
+            RetValSpec<EntryTypePtr>,
+            [
+                ArgSpec<EntryType>, 
+                ArgSpec<ActionType>
+            ]
+        >,
+        FunctionSpec<
+            "hsearch_r",
+            RetValSpec<IntType>,
+            [
+                ArgSpec<EntryType>, 
+                ArgSpec<ActionType>,
+                ArgSpec<EntryTypePtrPtr>,
+                ArgSpec<StructHsearchDataNamePtr>
+            ]
+        >,
+    ]
+  >; 
+
   HeaderSpec StdIO = HeaderSpec<
       "stdio.h",
       [], // Macros
@@ -1267,6 +1332,7 @@
     PThread,
     Signal,
     Spawn,
+    Search,
     StdIO,
     StdLib,
     SysIOctl,