Unix Prog: Process Times

1. System Definition:

 ubuntu@ip-172-31-23-227:~$ less /usr/include/x86_64-linux-gnu/sys/times.h  
 ......  
 /* Structure describing CPU time used by a process and its children. */  
 struct tms  
  {  
   clock_t tms_utime;     /* User CPU time. */  
   clock_t tms_stime;     /* System CPU time. */  
   
   clock_t tms_cutime;     /* User CPU time of dead children. */  
   clock_t tms_cstime;     /* System CPU time of dead children. */  
  };  
   
   
 /* Store the CPU time used by this process and all its  
   dead children (and their dead children) in BUFFER.  
   Return the elapsed real time, or (clock_t) -1 for errors.  
   All times are in CLK_TCKths of a second. */  
 extern clock_t times (struct tms *__buffer) __THROW;  
 ......  

2. Example

times.c:

 #include<stdio.h>  
 #include<stdlib.h>  
 #include<unistd.h>  
 #include<sys/times.h>  
   
 void pr_times(clock_t real, struct tms *tmstart, struct tms *tmend)  
 {  
  static long clktck = 0;  
   
  // Get the constant: number of clock tick per second  
  if(clktck == 0) {  
   if((clktck = sysconf(_SC_CLK_TCK)) < 0) {  
    printf("sysconf Error!\n");  
    exit(3);  
   }  
  }  
   
  printf("  real:  %7.2f\n", real / (double)clktck);  
  printf("  user:  %7.2f\n", (tmend->tms_utime - tmstart->tms_utime) / (double)clktck);  
  printf("  sys:  %7.2f\n", (tmend->tms_stime - tmstart->tms_stime) / (double)clktck);  
  printf("child user: %7.2f\n", (tmend->tms_cutime - tmstart->tms_cutime) / (double)clktck);  
  printf("child sys: %7.2f\n", (tmend->tms_cstime - tmstart->tms_cstime) / (double)clktck);  
 }  
   
 void do_cmd(char *cmd)  
 {  
  struct tms tmstart, tmend;  
  clock_t start ,end;  
  int status;  
   
  // Retrieve the current time information  
  printf("\ncommand: %s\n", cmd);  
  if((start = times(&tmstart)) == -1) {  
   printf("times error!\n");  
   exit(1);  
  }  
   
  // Run the command  
  if((status = system(cmd)) < 0) {  
   printf("system error!\n");  
   exit(2);  
  }  
   
  // Retrieve the time information after running the command  
  if((end = times(&tmend)) == -1) {  
   printf("times error!\n");  
   exit(1);  
  }  
   
  pr_times(end-start, &tmstart, &tmend);  
 }  
   
 int main(int argc, char* argv[])  
 {  
  int i;  
   
  setbuf(stdout, NULL);  
  for(i=1; i < argc; i++) {  
   do_cmd(argv[i]);  
  }  
  exit(0);  
 }  

shell:

 ubuntu@ip-172-31-23-227:~$ ./times.out "sleep 5"  
   
 command: sleep 5  
   real:   5.00  
   user:   0.00  
   sys:    0.00  
 child user:  0.00  
 child sys:   0.00