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snim2/clock_res.c

Created Apr 2, 2014
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Print available (Linux) system clock resolutions
/* Print a table of available timer frequencies. Linux only.
*
* (c) Sarah Mount <s.mount@wlv.ac.uk> 2014.
*/
#include <stdio.h>
#include <string.h>
#include <sys/utsname.h>
#include <time.h>
/* Print a horizontal rule. */
void hrule();
/* Print a fancy header above the table of results. */
void print_header();
/* Print resolutions of all clocks in the lookup table. */
void print_resolutions();
/* Lookup table containing clock IDs and readable names. */
typedef struct lut_t { clockid_t id; const char *name; } lut_t;
/* All available clocks listed in the man page for clock_getres. */
lut_t clocks[] = {
{ CLOCK_REALTIME, "CLOCK_REALTIME" },
{ CLOCK_REALTIME_COARSE, "CLOCK_REALTIME_COARSE" },
{ CLOCK_MONOTONIC, "CLOCK_MONOTONIC" },
{ CLOCK_MONOTONIC_COARSE, "CLOCK_MONOTONIC_COARSE" },
{ CLOCK_MONOTONIC_RAW, "CLOCK_MONOTONIC_RAW" },
{ CLOCK_BOOTTIME, "CLOCK_BOOTTIME" },
{ CLOCK_PROCESS_CPUTIME_ID, "CLOCK_PROCESS_CPUTIME_ID" },
{ CLOCK_THREAD_CPUTIME_ID, "CLOCK_THREAD_CPUTIME_ID" },
{ (clockid_t) -1, NULL },
};
int main(int argc, char** argv) {
print_header();
print_resolutions();
hrule();
printf("\n");
return 0;
}
/* Print resolutions of all clocks in the lookup table. */
void print_resolutions() {
struct timespec spec;
struct lut_t *p = NULL;
for (p = clocks; p->id != -1; ++p) {
if (clock_getres(p->id, &spec) != 0) {
printf("%s is not supported on this platform.\n", p->name);
}
else {
printf(" %-25s | %-10ld | %-10ld (%g secs)\n",
p->name,
spec.tv_sec,
spec.tv_nsec,
(double)spec.tv_nsec / (double)1000000000.0);
}
}
}
/* Print a fancy header above the table of results. */
void print_header() {
struct utsname sysinfo;
printf("\n");
hrule();
if (uname(&sysinfo) == 0) {
printf("\t%s system clock resolutions\n",
strcat(sysinfo.sysname, sysinfo.release));
} else {
printf("\tSystem clock resolutions\n");
}
hrule();
printf(" %-25s | %-10s | %-10s \n", "Clock", "Seconds", "Nanoseconds");
hrule();
}
/* Print a horizontal rule. */
void hrule() {
printf("----------------------------------------------------------------\n");
}
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