ref: 27b4662757e3d9a500b69a96057cef8fdeacca99
dir: /lib/c/syscall.h/
extern void *_brk(void *addr);
extern int _open(const char *path, int flags);
extern int _close(int fd);
extern int _read(int fd, void *buf, size_t n);
extern int _write(int fd, void *buf, size_t n);
extern int _lseek(int fd, long off, int whence);
extern void _Exit(int status);
extern int _access(char *path, int mode);
extern int raise(int sig);
extern void (*signal(int sig, void (*func)(int)))(int);
extern char *getenv(const char *var);
extern int rename(const char *from, const char *to);
extern int remove(const char *path);
/* auxiliar functions */
#ifdef stdin
extern FILE *_fpopen(const char * restrict fname,
const char * restrict mode,
FILE * restrict fp);
#endif
#define O_WRONLY 1
#define O_RDONLY 2
#define O_RDWR 4
#define O_TRUNC 8
#define O_APPEND 16
#define O_CREAT 32