ffi.C.fputs("test\n", io.stderr)
  ffi.C.fprintf(io.stderr, "Hello %s\n", "world")

local ffi = require "ffi"
 
ffi.cdef[[
typedef struct {
  char *fpos;
  void *base;
  unsigned short handle;
  short flags;
  short unget;
  unsigned long alloc;
  unsigned short buffincrement;
} FILE;
 
FILE *fopen(const char *filename, const char *mode);
int fprintf(FILE *stream, const char *format, ...);
int fclose(FILE *stream);
]]
 
local f = ffi.C.fopen("/tmp/test", "a+")
ffi.C.fprintf(f, "Hello World")
ffi.C.fclose(f)