Based on example 8.31 of APUE, suppose the following code. This example shows user/sys time of a process and also user/sys times of child processes for each command (passed as argvs)
#include <unistd.h>#include <stdlib.h>#include <stdio.h>#include <sys/times.h>void do_cmd(int, const char *);void pr_times(clock_t, clock_t, struct tms *, struct tms *);int main (int argc, char *argv[]) { long clktck = 0; clktck=sysconf(_SC_CLK_TCK); for (int i=1; i<argc; i++) do_cmd(clktck, argv[i]); exit (0);}void do_cmd(int clktck, const char *cmd) { struct tms tmsstart, tmsend; clock_t start, end; start=times(&tmsstart); system(cmd); end = times(&tmsend); printf("command:%s\n", cmd); pr_times(clktck, end-start, &tmsstart, &tmsend); printf("\n");}void pr_times(clock_t clktck, clock_t real, struct tms *start, struct tms *end) { printf("real:%7.2f\n", real/(double)clktck); printf("user:%7.2f\n", (end->tms_utime - start->tms_utime) / (double)clktck); // this line printf("sys:%7.2f\n", (end->tms_stime - start->tms_stime) / (double)clktck); // and this line printf("cuser:%7.2f\n", (end->tms_cutime- start->tms_cutime)/ (double)clktck); printf("csys:%7.2f\n", (end->tms_cstime- start->tms_cstime)/ (double)clktck);}My question is, by this scheme of command execution, is it possible to have user/sys time more than zero (and how) or always these two values is zero (becuase executed as forked(child process) ) ?
I execute the program like following
./a.out "sleep 10" "find / -name a* 1>/dev/null 2>&1" 'bash -c "for ((i=0;i<1000000;i++)); do :; done;" '
