UNIX Programming. struct timeval how to print it (

问题:

I am trying to print a value of type timeval. Actually I am able to print it, but I get the following warning:

Multiple markers at this line

• format ‘%ld’ expects type ‘long int’, but argument 2 has type ‘struct timeval’

The program compiles and it prints the values, but I would like to know if I am doing something wrong. Thanks.

    printf("%ld.%6ld\n",usage.ru_stime);
    printf("%ld.%6ld\n",usage.ru_utime);

where usage is of type

typedef struct{
    struct timeval ru_utime; /* user time used */
    struct timeval ru_stime; /* system time used */
    long   ru_maxrss;        /* maximum resident set size */
    long   ru_ixrss;         /* integral shared memory size */
    long   ru_idrss;         /* integral unshared data size */
    long   ru_isrss;         /* integral unshared stack size */
    long   ru_minflt;        /* page reclaims */
    long   ru_majflt;        /* page faults */
    long   ru_nswap;         /* swaps */
    long   ru_inblock;       /* block input operations */
    long   ru_oublock;       /* block output operations */
    long   ru_msgsnd;        /* messages sent */
    long   ru_msgrcv;        /* messages received */
    long   ru_nsignals;      /* signals received */
    long   ru_nvcsw;         /* voluntary context switches */
    long   ru_nivcsw;        /* involuntary context switches */
}rusage;

struct rusage usage;

回答1:

In the GNU C Library, struct timeval:

is declared in sys/time.h and has the following members:

long int tv_sec

This represents the number of whole seconds of elapsed time.

long int tv_usec

This is the rest of the elapsed time (a fraction of a second), represented as the number of microseconds. It is always less than one million.

So you will need to do

printf("%ld.%06ld\n", usage.ru_stime.tv_sec, usage.ru_stime.tv_usec);

to get a "nicely formatted" timestamp like 1.000123.

回答2:

Since struct timeval will be declared something like:

struct timeval {
    time_t      tv_sec;
    suseconds_t tv_usec;
}

you need to get at the underlying fields:

printf ("%ld.%06ld\n", usage.ru_stime.tv_sec, usage.ru_stime.tv_usec);
printf ("%ld.%06ld\n", usage.ru_utime.tv_sec, usage.ru_utime.tv_usec);

回答3:

yeah its

int main( void )
{
    clock_t start, stop;
    long int x;
    double duration;
    static struct timeval prev;
    struct timeval now;

    start = clock();  // get number of ticks before loop

    for( x = 0; x < 1000000000; x++ );
    // sleep(100);

    stop = clock();  // get number of ticks after loop

    // calculate time taken for loop
    duration = ( double ) ( stop - start ) / CLOCKS_PER_SEC;

    printf( "\nThe number of seconds for loop to run was %.2lf\n", duration );

    gettimeofday(&now, NULL);
    prev.tv_sec = duration;
    if (prev.tv_sec)
    {
        int diff = (now.tv_sec-prev.tv_sec)*1000+(now.tv_usec-prev.tv_usec)/1000;
        printf("DIFF %d\n",diff);
    }

    return 0;

}

回答4:

Yes , timeval is defined like this

struct timeval { 
    time_t      tv_sec; 
    suseconds_t tv_usec; 
} 

Using

printf ("%ld.%06ld\n", usage.ru_stime.tv_sec, usage.ru_stime.tv_usec); 

will surely of help.

回答5:

I just made up this handy little function from the info above. Self-contained except for needing time.h. Call it with the label you want wherever you want to know the time in your stdout stream.

void timestamp(char *lbl) { // just outputs time and label
  struct timeval tval;
  int rslt;
  rslt = gettimeofday(&tval,NULL);
  if (rslt) printf("gettimeofday error\n");
  printf("%s timestamp: %ld.%06ld\n", lbl, tval.tv_sec, tval.tv_usec);
}

Typical output looks like: dpyfunc got ftqmut timestamp: 1537394319.501560

And, you can surround the calls to it with a #ifdef to turn them on and off all at once by commenting out your #define. This could be useful almost like profiling but you can quickly disable it for production/release code. Like:

#define TIMEDUMPS

#ifdef TIMEDUMPS
timestamp("function 1 start");
#endif

#ifdef TIMEDUMPS
timestamp("function 2 start");
#endif

Comment out the #define TIMEDUMPS and it turns all of them off. No matter how many, in how many source code files.