getrusage

I just noticed this line in the getrusage man page: Including <sys/time.h> is not required these days, but increases portability. (Indeed, struct timeval is defined in <sys/time.h> ) What? Since struct rusage contains struct timeval as a member, surely sys/resource.h must include sys/time.h or the type would be incomplete and unusable? How could this comment ever have made sense? How could it ever have not been necessary? How could portability have ever been helped? In general, it was not uncommon in the early days of C for you to have to manually include header file A before header file B.

This is from man getrusage struct rusage { 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 */

I would like to measure the system time it takes to execute some code. To do this I know I would sandwich said code between two calls to getrusage(), but I get some unexpected results... #include <sys/time.h> #include <sys/resource.h> #include <unistd.h> #include <stdio.h> int main() { struct rusage usage; struct timeval start, end; int i, j, k = 0; getrusage(RUSAGE_SELF, &usage); start = usage.ru_stime; for (i = 0; i < 10000; i++) { /* Double loop for more interesting results. */ for (j = 0; j < 10000; j++) { k += 20; } } getrusage(RUSAGE_SELF, &usage); end = usage.ru_stime; printf("Started

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;