diff --git a/libc/include/llvm-libc-macros/fcntl-macros.h b/libc/include/llvm-libc-macros/fcntl-macros.h
--- a/libc/include/llvm-libc-macros/fcntl-macros.h
+++ b/libc/include/llvm-libc-macros/fcntl-macros.h
@@ -1,7 +1,7 @@
 #ifndef __LLVM_LIBC_MACROS_FCNTL_MACROS_H
 #define __LLVM_LIBC_MACROS_FCNTL_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/fcntl-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-macros/sched-macros.h b/libc/include/llvm-libc-macros/sched-macros.h
--- a/libc/include/llvm-libc-macros/sched-macros.h
+++ b/libc/include/llvm-libc-macros/sched-macros.h
@@ -9,7 +9,7 @@
 #ifndef __LLVM_LIBC_MACROS_SCHED_MACROS_H
 #define __LLVM_LIBC_MACROS_SCHED_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/sched-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-macros/sys-ioctl-macros.h b/libc/include/llvm-libc-macros/sys-ioctl-macros.h
--- a/libc/include/llvm-libc-macros/sys-ioctl-macros.h
+++ b/libc/include/llvm-libc-macros/sys-ioctl-macros.h
@@ -9,7 +9,7 @@
 #ifndef __LLVM_LIBC_MACROS_SYS_IOCTL_MACROS_H
 #define __LLVM_LIBC_MACROS_SYS_IOCTL_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/sys-ioctl-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-macros/sys-mman-macros.h b/libc/include/llvm-libc-macros/sys-mman-macros.h
--- a/libc/include/llvm-libc-macros/sys-mman-macros.h
+++ b/libc/include/llvm-libc-macros/sys-mman-macros.h
@@ -9,7 +9,7 @@
 #ifndef __LLVM_LIBC_MACROS_SYS_MMAN_MACROS_H
 #define __LLVM_LIBC_MACROS_SYS_MMAN_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/sys-mman-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-macros/sys-random-macros.h b/libc/include/llvm-libc-macros/sys-random-macros.h
--- a/libc/include/llvm-libc-macros/sys-random-macros.h
+++ b/libc/include/llvm-libc-macros/sys-random-macros.h
@@ -9,7 +9,7 @@
 #ifndef __LLVM_LIBC_MACROS_SYS_RANDOM_MACROS_H
 #define __LLVM_LIBC_MACROS_SYS_RANDOM_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/sys-random-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-macros/sys-resource-macros.h b/libc/include/llvm-libc-macros/sys-resource-macros.h
--- a/libc/include/llvm-libc-macros/sys-resource-macros.h
+++ b/libc/include/llvm-libc-macros/sys-resource-macros.h
@@ -9,7 +9,7 @@
 #ifndef __LLVM_LIBC_MACROS_SYS_RESOURCE_MACROS_H
 #define __LLVM_LIBC_MACROS_SYS_RESOURCE_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/sys-resource-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-macros/sys-socket-macros.h b/libc/include/llvm-libc-macros/sys-socket-macros.h
--- a/libc/include/llvm-libc-macros/sys-socket-macros.h
+++ b/libc/include/llvm-libc-macros/sys-socket-macros.h
@@ -9,7 +9,7 @@
 #ifndef __LLVM_LIBC_MACROS_SYS_SOCKET_MACROS_H
 #define __LLVM_LIBC_MACROS_SYS_SOCKET_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/sys-socket-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-macros/sys-stat-macros.h b/libc/include/llvm-libc-macros/sys-stat-macros.h
--- a/libc/include/llvm-libc-macros/sys-stat-macros.h
+++ b/libc/include/llvm-libc-macros/sys-stat-macros.h
@@ -9,7 +9,7 @@
 #ifndef __LLVM_LIBC_MACROS_SYS_STAT_MACROS_H
 #define __LLVM_LIBC_MACROS_SYS_STAT_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/sys-stat-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-macros/sys-time-macros.h b/libc/include/llvm-libc-macros/sys-time-macros.h
--- a/libc/include/llvm-libc-macros/sys-time-macros.h
+++ b/libc/include/llvm-libc-macros/sys-time-macros.h
@@ -9,7 +9,7 @@
 #ifndef __LLVM_LIBC_MACROS_SYS_TIME_MACROS_H
 #define __LLVM_LIBC_MACROS_SYS_TIME_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/sys-time-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-macros/time-macros.h b/libc/include/llvm-libc-macros/time-macros.h
--- a/libc/include/llvm-libc-macros/time-macros.h
+++ b/libc/include/llvm-libc-macros/time-macros.h
@@ -1,7 +1,7 @@
 #ifndef __LLVM_LIBC_MACROS_TIME_MACROS_H
 #define __LLVM_LIBC_MACROS_TIME_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/time-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-macros/unistd-macros.h b/libc/include/llvm-libc-macros/unistd-macros.h
--- a/libc/include/llvm-libc-macros/unistd-macros.h
+++ b/libc/include/llvm-libc-macros/unistd-macros.h
@@ -1,7 +1,7 @@
 #ifndef __LLVM_LIBC_MACROS_UNISTD_MACROS_H
 #define __LLVM_LIBC_MACROS_UNISTD_MACROS_H
 
-#ifdef __unix__
+#ifdef __linux__
 #include "linux/unistd-macros.h"
 #endif
 
diff --git a/libc/include/llvm-libc-types/struct_dirent.h b/libc/include/llvm-libc-types/struct_dirent.h
--- a/libc/include/llvm-libc-types/struct_dirent.h
+++ b/libc/include/llvm-libc-types/struct_dirent.h
@@ -14,7 +14,7 @@
 
 struct dirent {
   ino_t d_ino;
-#ifdef __unix__
+#ifdef __linux__
   off_t d_off;
   unsigned short d_reclen;
 #endif
diff --git a/libc/include/llvm-libc-types/struct_utsname.h b/libc/include/llvm-libc-types/struct_utsname.h
--- a/libc/include/llvm-libc-types/struct_utsname.h
+++ b/libc/include/llvm-libc-types/struct_utsname.h
@@ -9,7 +9,7 @@
 #ifndef __LLVM_LIBC_TYPES_STRUCT_UTSNAME_H__
 #define __LLVM_LIBC_TYPES_STRUCT_UTSNAME_H__
 
-#ifdef __unix__
+#ifdef __linux__
 #define __UTS_NAME_LENGTH 65
 #else
 // Arbitray default. Should be specialized for each platform.
@@ -22,7 +22,7 @@
   char release[__UTS_NAME_LENGTH];
   char version[__UTS_NAME_LENGTH];
   char machine[__UTS_NAME_LENGTH];
-#ifdef __unix__
+#ifdef __linux__
   char domainname[__UTS_NAME_LENGTH];
 #endif
 };
diff --git a/libc/src/__support/File/dir.cpp b/libc/src/__support/File/dir.cpp
--- a/libc/src/__support/File/dir.cpp
+++ b/libc/src/__support/File/dir.cpp
@@ -39,7 +39,7 @@
     return nullptr;
 
   struct ::dirent *d = reinterpret_cast<struct ::dirent *>(buffer + readptr);
-#ifdef __unix__
+#ifdef __linux__
   // The d_reclen field is available on Linux but not required by POSIX.
   readptr += d->d_reclen;
 #else
diff --git a/libc/src/__support/OSUtil/io.h b/libc/src/__support/OSUtil/io.h
--- a/libc/src/__support/OSUtil/io.h
+++ b/libc/src/__support/OSUtil/io.h
@@ -15,7 +15,7 @@
 #include "gpu/io.h"
 #elif defined(__APPLE__)
 #include "darwin/io.h"
-#elif defined(__unix__)
+#elif defined(__linux__)
 #include "linux/io.h"
 #elif defined(__Fuchsia__)
 #include "fuchsia/io.h"
diff --git a/libc/src/__support/OSUtil/quick_exit.h b/libc/src/__support/OSUtil/quick_exit.h
--- a/libc/src/__support/OSUtil/quick_exit.h
+++ b/libc/src/__support/OSUtil/quick_exit.h
@@ -15,7 +15,7 @@
 #include "gpu/quick_exit.h"
 #elif defined(__APPLE__)
 #include "darwin/quick_exit.h"
-#elif defined(__unix__)
+#elif defined(__linux__)
 #include "linux/quick_exit.h"
 #endif
 
diff --git a/libc/src/__support/OSUtil/syscall.h b/libc/src/__support/OSUtil/syscall.h
--- a/libc/src/__support/OSUtil/syscall.h
+++ b/libc/src/__support/OSUtil/syscall.h
@@ -11,7 +11,7 @@
 
 #ifdef __APPLE__
 #include "darwin/syscall.h"
-#elif defined(__unix__)
+#elif defined(__linux__)
 #include "linux/syscall.h"
 #endif