85 lines
2.1 KiB
C
85 lines
2.1 KiB
C
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/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* This file is in the public domain.
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*
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* You don't have to, but if you feel like
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* acknowledging where you got this code, you may
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* reference me by name, email address, or point
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* people to the course website:
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* https://stevens.netmeister.org/631/
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*/
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#include <err.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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/* ISO 8601 format is "YYYY-MM-DDTHH:MM:SSZ" */
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#define ISO8601_LENGTH 20 + 1 /* +1 for NULL */
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int
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main() {
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time_t t;
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struct timeval tv;
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struct timespec ts;
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struct tm *tm;
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char buf[ISO8601_LENGTH];
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if ((t = time(NULL)) < 0) {
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err(EXIT_FAILURE, "unable to call time()");
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/* NOTREACHED */
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}
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(void)printf("time(3) says: %ld\n", t);
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if (gettimeofday(&tv, NULL) < 0) {
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err(EXIT_FAILURE, "unable to gettimeofday()");
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/* NOTREACHED */
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}
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(void)printf("gettimeofday(2) says: %ld.%d\n", tv.tv_sec, tv.tv_usec);
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if (clock_gettime(CLOCK_REALTIME, &ts) < 0) {
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err(EXIT_FAILURE, "unable to call clock_gettime(2)");
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/* NOTREACHED */
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}
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(void)printf("clock_gettime(2) says: %ld.%ld\n\n", ts.tv_sec, ts.tv_nsec);
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if ((tm = gmtime(&t)) == NULL) {
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err(EXIT_FAILURE, "unable to call gmtime()");
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/* NOTREACHED */
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}
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(void)printf("asctime(3) says: %s", asctime(tm));
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if ((tm = localtime(&t)) == NULL) {
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err(EXIT_FAILURE, "unable to call gmtime()");
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/* NOTREACHED */
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}
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(void)printf("localtime is: %s", asctime(tm));
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tm->tm_sec = 0;
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tm->tm_min = 0;
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tm->tm_hour = 0;
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tm->tm_mday = 1;
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tm->tm_mon = 0;
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tm->tm_year = 70;
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tm->tm_isdst = 0;
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if ((t = mktime(tm)) < 0) {
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err(EXIT_FAILURE, "unable to call mktime()");
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/* NOTREACHED */
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}
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(void)printf("epoch date is: %s", ctime(&t));
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if ((strftime(buf, ISO8601_LENGTH, "%Y-%m-%dT%H:%M:%SZ", tm)) == 0) {
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err(EXIT_FAILURE, "strftime failed");
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/* NOTREACHED */
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}
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(void)printf("ISO8601 formatted: %s\n", buf);
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return EXIT_SUCCESS;
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}
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