42-timers.rar

/*************************************************************************\ * Copyright (C) Michael Kerrisk, 2017. * * * * This program is free software. You may use, modify, and redistribute it * * under the terms of the GNU General Public License as published by the * * Free Software Foundation, either version 3 or (at your option) any * * later version. This program is distributed without any warranty. See * * the file COPYING.gpl-v3 for details. * \*************************************************************************/ /* Listing 23-1 */ #include <signal.h> #include <sys/time.h> #include <time.h> #include "tlpi_hdr.h" static volatile sig_atomic_t gotAlarm = 0; /* Set nonzero on receipt of SIGALRM */ /* Retrieve and display the real time, and (if 'includeTimer' is TRUE) the current value and interval for the ITIMER_REAL timer */ static void displayTimes(const char *msg, Boolean includeTimer) { struct itimerval itv; static struct timeval start; struct timeval curr; static int callNum = 0; /* Number of calls to this function */ if (callNum == 0) /* Initialize elapsed time meter */ if (gettimeofday(&start, NULL) == -1) errExit("gettimeofday"); if (callNum % 20 == 0) /* Print header every 20 lines */ printf(" Elapsed Value Interval\n"); if (gettimeofday(&curr, NULL) == -1) errExit("gettimeofday"); printf("%-7s %6.2f", msg, curr.tv_sec - start.tv_sec + (curr.tv_usec - start.tv_usec) / 1000000.0); if (includeTimer) { if (getitimer(ITIMER_REAL, &itv) == -1) errExit("getitimer"); printf(" %6.2f %6.2f", itv.it_value.tv_sec + itv.it_value.tv_usec / 1000000.0, itv.it_interval.tv_sec + itv.it_interval.tv_usec / 1000000.0); } printf("\n"); callNum++; } static void sigalrmHandler(int sig) { gotAlarm = 1; } int main(int argc, char *argv[]) { struct itimerval itv; clock_t prevClock; int maxSigs; /* Number of signals to catch before exiting */ int sigCnt; /* Number of signals so far caught */ struct sigaction sa; if (argc > 1 && strcmp(argv[1], "--help") == 0) usageErr("%s [secs [usecs [int-secs [int-usecs]]]]\n", argv[0]); sigCnt = 0; sigemptyset(&sa.sa_mask); sa.sa_flags = 0; sa.sa_handler = sigalrmHandler; if (sigaction(SIGALRM, &sa, NULL) == -1) errExit("sigaction"); /* Set timer from the command-line arguments */ itv.it_value.tv_sec = (argc > 1) ? getLong(argv[1], 0, "secs") : 2; itv.it_value.tv_usec = (argc > 2) ? getLong(argv[2], 0, "usecs") : 0; itv.it_interval.tv_sec = (argc > 3) ? getLong(argv[3], 0, "int-secs") : 0; itv.it_interval.tv_usec = (argc > 4) ? getLong(argv[4], 0, "int-usecs") : 0; /* Exit after 3 signals, or on first signal if interval is 0 */ maxSigs = (itv.it_interval.tv_sec == 0 && itv.it_interval.tv_usec == 0) ? 1 : 3; displayTimes("START:", FALSE); if (setitimer(ITIMER_REAL, &itv, NULL) == -1) errExit("setitimer"); prevClock = clock(); sigCnt = 0; for (;;) { /* Inner loop consumes at least 0.5 seconds CPU time */ while (((clock() - prevClock) * 10 / CLOCKS_PER_SEC) < 5) { if (gotAlarm) { /* Did we get a signal? */ gotAlarm = 0; displayTimes("ALARM:", TRUE); sigCnt++; if (sigCnt >= maxSigs) { printf("That's all folks\n"); exit(EXIT_SUCCESS); } } } prevClock = clock(); displayTimes("Main: ", TRUE); } }