我已经从GNU库中拿出了这个例子。我想知道他们为什么在设置信号处理函数时第一次调用signal()函数两次,第一次调用main()函数,第二次调用函数本身。使用处理函数内部的signal()函数
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
/* This flag controls termination of the main loop. */
volatile sig_atomic_t keep_going = 1;
/* The signal handler just clears the flag and re-enables itself. */
void
catch_alarm (int sig)
{
keep_going = 0;
signal (sig, catch_alarm);
}
void
do_stuff (void)
{
puts ("Doing stuff while waiting for alarm....");
}
int
main (void)
{
/* Establish a handler for SIGALRM signals. */
signal (SIGALRM, catch_alarm);
/* Set an alarm to go off in a little while. */
alarm (2);
/* Check the flag once in a while to see when to quit. */
while (keep_going)
do_stuff();
return EXIT_SUCCESS;
}
现在我的代码......
void createTimer(long freq_nanosec)
{
timer_t timerid;
struct sigevent sev;
struct itimerspec timerint;
struct sigaction saction;
/* Establish handler for timer signal */
saction.sa_flags = 0;
saction.sa_handler = OnTimer;
sigemptyset(&saction.sa_mask);
sigaddset (&saction.sa_mask, SIGIO);
if (sigaction(SIGALRM, &saction, NULL) == -1) error("sigaction");
else printf("OnTimer handler created\n");
/* Create real time signal */
sev.sigev_notify = SIGEV_SIGNAL;
sev.sigev_signo = SIGALRM;
sev.sigev_value.sival_ptr = &timerid;
if (timer_create(CLOCKID, &sev, &timerid) == -1) error("timer_create");
else printf("timer ID is 0x%lx\n", (long) timerid);
/* Arm the timer */
timerint.it_value.tv_sec = timerint.it_interval.tv_sec =
freq_nanosec/1000000000;
timerint.it_value.tv_nsec = timerint.it_interval.tv_nsec =
freq_nanosec % 1000000000;
if (timer_settime(timerid, 0, &timerint, NULL) == -1)
error("timer_settime");
else printf("Timer armed\n");
}
这是否意味着每当调用信号处理函数时,该信号动作就会被释放为默认值?这很奇怪,因为当我每次使用计时器信号时都会一次又一次地调用处理程序。而且我不会在处理程序中恢复定时器信号。你能否详细说明一下? –
如何设置定时器信号的处理程序? – mtrw
请在上面找到我的代码 –