diff --git a/format.cc b/format.cc
index 1a6e4e22..124d552f 100644
--- a/format.cc
+++ b/format.cc
@@ -487,6 +487,11 @@ FMT_FUNC int fmt::internal::UTF16ToUTF8::convert(fmt::WStringRef s) {
   return 0;
 }
 
+# ifdef __GNUC__
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wshadow"
+# endif
+
 FMT_FUNC void fmt::WindowsError::init(
     int error_code, StringRef format_str, ArgList args) {
   error_code_ = error_code;
@@ -496,6 +501,10 @@ FMT_FUNC void fmt::WindowsError::init(
   base = std::runtime_error(w.str());
 }
 
+# ifdef __GNUC__
+#  pragma GCC diagnostic pop
+# endif
+
 #endif
 
 FMT_FUNC void fmt::internal::format_system_error(
diff --git a/posix.cc b/posix.cc
index b4893cd6..be5f8eba 100644
--- a/posix.cc
+++ b/posix.cc
@@ -30,7 +30,7 @@
 
 #include "posix.h"
 
-#include <limits.h>
+#include <climits>
 #include <sys/types.h>
 #include <sys/stat.h>
 
@@ -96,12 +96,35 @@ void fmt::BufferedFile::close() {
 }
 
 int fmt::BufferedFile::fileno() const {
+  assert(file_ && "File has been closed");
   int fd = FMT_POSIX_CALL(fileno(file_));
   if (fd == -1)
     throw SystemError(errno, "cannot get file descriptor");
   return fd;
 }
 
+void fmt::BufferedFile::flush() const {
+  assert(file_ && "File has been closed");
+  if (FMT_SYSTEM(fflush(file_)) != 0) {
+    throw SystemError(errno, "cannot flush file");
+  }
+}
+
+void fmt::BufferedFile::write(fmt::StringRef str) {
+  assert(file_ && "File has been closed");
+  size_t result = FMT_SYSTEM(fwrite(str.c_str(), str.size(), 1, file_));
+  if (result < str.size()) {
+    // FIXME: Will fwrite set errno?
+    throw SystemError(errno, "failed to write raw string, only {} character(s) written", result);
+  }
+}
+
+void fmt::BufferedFile::write(char c) {
+  assert(file_ && "File has been closed");
+  if (FMT_SYSTEM(fputc(c, file_)) == EOF)
+    throw SystemError(errno, "failed to write '{}'", c);
+}
+
 fmt::File::File(fmt::StringRef path, int oflag) {
   int mode = S_IRUSR | S_IWUSR;
 #ifdef _WIN32
@@ -134,13 +157,13 @@ void fmt::File::close() {
 
 fmt::LongLong fmt::File::size() const {
 #ifdef _WIN32
-  LARGE_INTEGER size = {};
+  LARGE_INTEGER filesize = {};
   HANDLE handle = reinterpret_cast<HANDLE>(_get_osfhandle(fd_));
-  if (!FMT_SYSTEM(GetFileSizeEx(handle, &size)))
+  if (!FMT_SYSTEM(GetFileSizeEx(handle, &filesize)))
     throw WindowsError(GetLastError(), "cannot get file size");
-  FMT_STATIC_ASSERT(sizeof(fmt::LongLong) >= sizeof(size.QuadPart),
+  FMT_STATIC_ASSERT(sizeof(fmt::LongLong) >= sizeof(filesize.QuadPart),
       "return type of File::size is not large enough");
-  return size.QuadPart;
+  return filesize.QuadPart;
 #else
   typedef struct stat Stat;
   Stat file_stat = Stat();
@@ -228,7 +251,7 @@ fmt::BufferedFile fmt::File::fdopen(const char *mode) {
 
 long fmt::getpagesize() {
 #ifdef _WIN32
-  SYSTEM_INFO si = {};
+  SYSTEM_INFO si;
   GetSystemInfo(&si);
   return si.dwPageSize;
 #else
diff --git a/posix.h b/posix.h
index a2cf2b13..6d0e4dab 100644
--- a/posix.h
+++ b/posix.h
@@ -33,6 +33,7 @@
 #include <stdio.h>
 
 #include <cstddef>
+#include <cassert>
 
 #include "format.h"
 
@@ -43,9 +44,9 @@
 #ifndef FMT_POSIX
 # ifdef _WIN32
 // Fix warnings about deprecated symbols.
-#  define FMT_POSIX(call) _##call
+#  define FMT_POSIX(symbol) _##symbol
 # else
-#  define FMT_POSIX(call) call
+#  define FMT_POSIX(symbol) symbol
 # endif
 #endif
 
@@ -53,7 +54,7 @@
 #ifdef FMT_SYSTEM
 # define FMT_POSIX_CALL(call) FMT_SYSTEM(call)
 #else
-# define FMT_SYSTEM(call) call
+# define FMT_SYSTEM(call) ::call
 # ifdef _WIN32
 // Fix warnings about deprecated symbols.
 #  define FMT_POSIX_CALL(call) ::_##call
@@ -188,12 +189,34 @@ public:
   // Returns the pointer to a FILE object representing this file.
   FILE *get() const FMT_NOEXCEPT { return file_; }
 
+  // Returns the system file number of this file
   int fileno() const;
 
+  // Flushes the buffer of this file
+  void flush() const;
+
+  // Writes raw string without formatting
+  void write(fmt::StringRef str);
+
+  // Writes a single charactor without formatting
+  void write(char c);
+
+  // Writes a new line
+  void writeln() {
+    write('\n');
+  }
+
   void print(fmt::StringRef format_str, const ArgList &args) {
+    assert(file_ && "File has been closed");
     fmt::print(file_, format_str, args);
   }
+  void printf(fmt::StringRef format_str, const ArgList &args) {
+    assert(file_ && "File has been closed");
+    fmt::fprintf(file_, format_str, args);
+  }
+
   FMT_VARIADIC(void, print, fmt::StringRef)
+  FMT_VARIADIC(void, printf, fmt::StringRef)
 };
 
 // A file. Closed file is represented by a File object with descriptor -1.
diff --git a/test/posix-test.cc b/test/posix-test.cc
index c9529688..fe18cd62 100644
--- a/test/posix-test.cc
+++ b/test/posix-test.cc
@@ -178,6 +178,18 @@ int test::fileno(FILE *stream) {
   return ::FMT_POSIX(fileno(stream));
 }
 
+int test::fflush(FILE *stream) {
+  return ::fflush(stream);
+}
+
+int test::fwrite(const void *str, size_t size, size_t count, FILE *stream) {
+  return ::fwrite(str, size, count, stream);
+}
+
+int test::fputc(int ch, FILE *stream) {
+  return ::fputc(ch, stream);
+}
+
 #ifndef _WIN32
 # define EXPECT_RETRY(statement, func, message) \
     func##_count = 1; \
diff --git a/test/posix-test.h b/test/posix-test.h
index 4768cb94..7ab69bcb 100644
--- a/test/posix-test.h
+++ b/test/posix-test.h
@@ -73,7 +73,10 @@ int pipe(int *pfds, unsigned psize, int textmode);
 FILE *fopen(const char *filename, const char *mode);
 int fclose(FILE *stream);
 int fileno(FILE *stream);
+int fflush(FILE *stream);
 
+int fwrite(const void *str, size_t size, size_t count, FILE *stream);
+int fputc(int ch, FILE *stream);
 }  // namespace test
 
 #define FMT_SYSTEM(call) test::call
diff --git a/test/util-test.cc b/test/util-test.cc
index fd295525..8b8a20a1 100644
--- a/test/util-test.cc
+++ b/test/util-test.cc
@@ -699,9 +699,8 @@ void test_count_digits() {
 }
 
 TEST(UtilTest, StringRef) {
-  char space[100];
-  std::strcpy(space, "some string");
-  EXPECT_EQ(sizeof("some string") - 1, StringRef(space).size());
+  char space[100] = "some string";
+  EXPECT_EQ(std::strlen(space), StringRef(space).size());
 }
 
 TEST(UtilTest, CountDigits) {