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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/prctl.h>
#define NS (1L)
#define US (1000L)
#define MS (1000L * 1000L)
#define S (1000L * 1000L * 1000L)
static void usage(void)
{
printf("USAGE: slack (get | GET | ((reset | <interval>) [--fatal] [--] <command...>))\n");
printf("\n");
printf("The <interval> must be a positive number optionally with a suffix:\n");
printf(" ns n nanoseconds (default)\n");
printf(" µs µ us u microseconds\n");
printf(" ms m milliseconds\n");
printf(" s seconds\n");
printf("\n");
printf("If `GET' is used rather than `get', the timer slack value will be printed in\n");
printf("nanoseconds without suffix. `GET' and `get' prints the current timer slack\n");
printf("value and exits.\n");
printf("\n");
printf("`reset` reset the timer slack value to the default (the time slack value for\n");
printf("the init process (PID 1) has.)\n");
printf("\n");
printf("Unless `--fatal` is used, the program will run <command> even if the timer\n");
printf("slack could not be set.\n");
printf("\n");
}
int main(int argc, char** argv)
{
long slackvalue, r;
int i, j, fatal = 0;
char** exec_argv;
if ((argc < 2) || !strcmp(argv[1], "--help") || !strcmp(argv[1], "help"))
return usage(), argc < 2 ? 1 : 0;
if (!strcmp(argv[1], "get") || !strcmp(argv[1], "GET"))
{
const char* suffix;
if (r = prctl(PR_GET_TIMERSLACK), r < 0)
perror(*argv);
else
{
if (!strcmp(argv[1], "GET"))
suffix = "";
else if (r % S == 0) suffix = "s", r /= S;
else if (r % MS == 0) suffix = "ms", r /= MS;
else if (r % US == 0) suffix = "µs", r /= US;
else suffix = "ns";
printf("%li%s\n", r, suffix);
}
return r > 0 ? 0 : 1;
}
for (i = 2; i < argc; i++)
if (!strcmp(argv[i], "--fatal"))
fatal = 1;
else if (!strcmp(argv[i], "--"))
{
i++;
break;
}
else if (strstr(argv[i], "-") == argv[i])
return usage(), 1;
else
break;
if (i == argc)
return usage(), 1;
exec_argv = malloc((argc - i + 1) * sizeof(char*));
if (exec_argv == NULL)
return perror(*argv), 2;
exec_argv[argc - i] = NULL;
for (j = 0; i < argc; j++, i++)
exec_argv[j] = argv[i];
if (!strcmp(argv[1], "reset"))
slackvalue = 0;
else
{
char* end;
slackvalue = strtol(argv[1], &end, 10);
if (end == argv[1])
return fprintf(stderr, "No slack value specified."), free(exec_argv), 1;
if (!strcmp(end, "n") || !strcmp(end, "ns") || !strcmp(end, "")) slackvalue *= NS;
else if (!strcmp(end, "µ") || !strcmp(end, "µs")) slackvalue *= US;
else if (!strcmp(end, "u") || !strcmp(end, "us")) slackvalue *= US;
else if (!strcmp(end, "m") || !strcmp(end, "ms")) slackvalue *= MS;
else if (!strcmp(end, "s")) slackvalue *= S;
else
return fprintf(stderr, "Unrecognised suffix for slack value."), free(exec_argv), 1;
if (slackvalue <= 0)
return fprintf(stderr, "Invalid slack value: %lins", slackvalue), free(exec_argv), 1;
}
if (r = prctl(PR_SET_TIMERSLACK, slackvalue), r < 0)
if (perror(*argv), fatal)
return free(exec_argv), 2;
execvp(*exec_argv, exec_argv);
perror(*argv);
free(exec_argv);
return 2;
}
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