S_ISREG
#define S_ISREG(m) ((m & 0170000) == 0100000) /* regular file */
# define S_ISREG(mode) (((mode) & (_S_IFMT)) == (_S_IFREG))
#define S_ISREG(m) ((m) & S_IFREG)
#define S_ISREG(m) ((m) & S_IFREG)
#define S_ISREG(m) (((m) & 0170000) == 0100000) /* regular file */