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A variant of time(1) to measure startup precisely, able to show real time in milliseconds and max RSS in MB. Moved to
#include <sys/time.h>
#include <sys/types.h>
#include <sys/resource.h>
#include <sys/wait.h>
#include <spawn.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <unistd.h>
#define CHECK(cmd) if (cmd) { perror(#cmd); return 1; }
extern char **environ;
struct stats {
long average;
long min;
long max;
struct stats stats(long values[], int n) {
long min = values[0];
long max = values[0];
long sum = 0L;
for (int i = 0; i < n; i++) {
long value = values[i];
if (value < min)
min = value;
if (value > max)
max = value;
sum += value;
struct stats s = {sum/n, min, max};
return s;
int main(int argc, char *const argv[]) {
char *self = argv[0];
int n = 1;
if (argc > 0 && argv[0][0] >= '1' && argv[0][0] <= '9') {
n = atoi(argv[0]);
if (argc < 1) {
printf(" %s [REPEAT=1] /full/path/to/command ARGS...\n", self);
printf(" %s [REPEAT=1] `which command` ARGS...\n", self);
return 1;
struct rusage usage;
struct timespec before, after;
long realtime[n];
long memory[n];
pid_t pid;
int status;
long ns_to_ms = 1000000L;
for (int i = 0; i < n; i++) {
CHECK(clock_gettime(CLOCK_MONOTONIC, &before));
CHECK(posix_spawn(&pid, argv[0], NULL, NULL, argv, environ));
CHECK(waitpid(pid, &status, 0) == -1);
CHECK(clock_gettime(CLOCK_MONOTONIC, &after));
CHECK(getrusage(RUSAGE_CHILDREN, &usage));
realtime[i] = (after.tv_sec-before.tv_sec) * 1000000000L +
(long) (after.tv_nsec-before.tv_nsec);
printf("%ld ", (realtime[i]/ns_to_ms));
memory[i] = usage.ru_maxrss;
struct stats ts = stats(realtime, n);
struct stats ms = stats(memory, n);
#ifdef __APPLE__
long rss_to_mb = 1024L * 1024L;
long rss_to_mb = 1024L;
printf("%ld [%ld-%ld] ms\n", (ts.average/ns_to_ms), (ts.min/ns_to_ms), (ts.max/ns_to_ms));
printf("%ld [%ld-%ld] MB\n", (ms.average/rss_to_mb), (ms.min/rss_to_mb), (ms.max/rss_to_mb));
return 0;
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