LinuxÏÂʱ¼ä¶ÈÁ¿µÄÉîÈë·ÖÎö

Ò»)ANSI clockº¯Êý
1)¸ÅÊö:
clock º¯ÊýµÄ·µ»ØÖµÀàÐÍÊÇclock_t,Ëü³ýÒÔCLOCKS_PER_SECÀ´µÃ³öʱ¼ä,Ò»°ãÓÃÁ½´Îclockº¯ÊýÀ´¼ÆËã½ø³Ì×ÔÉíÔËÐеÄʱ¼ä.
ANSI clockÓÐÈý¸öÎÊÌâ:
1)Èç¹û³¬¹ýÒ»¸öСʱ,½«Òªµ¼ÖÂÒç³ö.
2)º¯ÊýclockûÓп¼ÂÇCPU±»×Ó½ø³ÌʹÓõÄÇé¿ö.
3)Ò²²»ÄÜÇø·ÖÓû§¿Õ¼äºÍÄں˿ռä.
ËùÒÔclockº¯ÊýÔÚlinuxϵͳÉϱäµÃûÓÐÒâÒå.
2)²âÊÔ
±àдtest1.c³ÌÐò,²âÊÔ²ÉÓÃclockº¯ÊýµÄÊä³öÓëtime³ÌÐòµÄÇø±ð.
vi test1.c
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main( void )
{
   long i=1000L;
   clock_t start, finish;
   double  duration;
   printf( "Time to do %ld empty loops is ", i );
   start = clock();
   while (--i){
    system("cd");
   }
   finish = clock();
   duration = (double)(finish - start) / CLOCKS_PER_SEC;
   printf( "%f seconds\n", duration );
   return 0;
}
gcc test1.c -o test1
time ./test1
Time to do 1000 empty loops is 0.180000 seconds
real    0m3.492s
user    0m0.512s
sys     0m2.972s
3)×ܽá:
(1)³ÌÐòµ÷Óà system("cd");£¬ÕâÀïÖ÷ÒªÊÇϵͳģʽ×Ó½ø³ÌµÄÏûºÄ,test1³ÌÐò²»ÄÜÌåÏÖÕâÒ»µã.
(2)0.180000 secondsÃëµÄÏûºÄÊÇÁ½´Îclock()º¯Êýµ÷ÓóýÒÔCLOCKS_PER_SEC.
(3)clock()º¯Êý·µ»ØÖµÊÇÒ»¸öÏà¶Ôʱ¼ä£¬¶ø²»ÊǾø¶Ôʱ¼ä.
(4)CLOCKS_PER_SECÊÇϵͳ¶¨ÒåµÄºê£¬ÓÉGNU±ê×¼¿â¶¨ÒåΪ1000000.
¶þ)times()ʱ¼äº¯Êý
1)¸ÅÊö:
Ô­ÐÍÈçÏ£º
clock_t times(struct tms *buf);
tms½á¹¹ÌåÈçÏÂ:
strace tms{
 clock_t tms_utime;
 clock_t tms_stime;
 clock_t tms_cutime;
 clock_t tms_cstime;
}
×¢ÊÍ:
tms_utime¼Ç¼µÄÊǽø³ÌÖ´ÐÐÓû§´úÂëµÄʱ¼ä.
tms_stime¼Ç¼µÄÊǽø³ÌÖ´ÐÐÄں˴úÂëµÄʱ¼ä.
tms_cutime¼Ç¼µÄÊÇ×Ó½ø³ÌÖ´ÐÐÓû§´úÂëµÄʱ¼ä.
tms_cstime¼Ç¼µÄÊÇ×Ó½ø³ÌÖ´ÐÐÄں˴úÂëµÄʱ¼ä.
2)²âÊÔ:
vi test2.c
#include <sys/times.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>
static void do_cmd(char *);
st