Linux中的延时函数

应用层：
   #include <unistd.h>

 

1、unsigned int sleep(unsigned int seconds); 秒级

   2、int usleep(useconds_t usec);              微秒级：1/10^-6

 
   #define _POSIX_C_SOURCE 199309

   #include <time.h>

   3、int nanosleep(const struct timespec *req, struct timespec *rem);
       struct timespec {
                  time_t tv_sec;        /* seconds */
                  long   tv_nsec;       /* nanoseconds */
              };
       // The value of the nanoseconds field must be in the range 0 to 999999999.

 
 内核层：
   include <linux/delay.h>
   1、void ndelay(unsigned long nsecs);         纳秒级：1/10^-10
   2、void udelay(unsigned long usecs);         微秒级: 1/10^-6
   3、void mdelay(unsigned long msecs);         毫秒级：1/10^-3