linux延时函数

#include<unistd.h>
 
   1、unsigned int sleep(unsignedint seconds); 秒级
   2、int usleep(useconds_tusec);             微秒级：1/10^-6

 
   #define _POSIX_C_SOURCE199309
   #include<time.h>
   3、int nanosleep(const structtimespec *req, struct timespec *rem);
      struct timespec {
                 time_ttv_sec;       
                 long  tv_nsec;      
             };
      // The value of the nanoseconds field must be in the range 0 to999999999.
 
 内核层：
   include<linux/delay.h>
   1、void ndelay(unsigned longnsecs);        纳秒级：1/10^-10
   2、void udelay(unsigned longusecs);        微秒级: 1/10^-6
   3、void mdelay(unsigned longmsecs);        毫秒级：1/10^-3