alarm(0)会产生SIGALRM信号吗？

samuel1004

#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
static void sig_alrm(int);

int
main(void)
{
    unsigned int nsec;
    signal(SIGALRM,sig_alrm);
    nsec = alarm(0);
    sleep(2);
    printf("alarm: %u\n", nsec);

    exit(0);
}

static void
sig_alrm(int signo)
{
    printf("SIGALAM Generated!\n");
        return;
}
执行结果：

alarm: 0
没有输出"SIGALAM Generated!\n"，是不是不产生SIGALRM信号？

akei48

关注一下，帮你顶。

kingwha

man alarm
  "unsigned int alarm(unsigned int seconds);
   If seconds is zero, no new alarm() is scheduled."
可见alarm(0)相当于禁用 alarm，不会产生alarm的signal。

samuel1004

自己搞清楚了。。
man 3 alarm

DESCRIPTION
     This interface is made obsolete by setitimer(2).

     The alarm() function sets a timer to deliver the signal SIGALRM to the
     calling process after the specified number of seconds.  If an alarm has
     already been set with alarm() but has not been delivered, another call to
     alarm() will supersede the prior call.  The request alarm(0) voids the
     current alarm and the signal SIGALRM will not be delivered.

zx_wing

原帖由 samuel1004 于 2007-4-17 15:07 发表
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
static void sig_alrm(int);

int
main(void)
{
    unsigned int nsec;
    signal(SIGALRM,sig_alrm);
    nsec = a ...

以后遇到系统调用的问题，应该先请教man，再发到论坛上来。不能偷懒，不然别人不会给回复。

1. 
   
2. alarm arranges for a SIGALRM signal to be delivered to the process in seconds seconds.
   
3. 
   
4. If seconds is zero, no new alarm is scheduled.
   

复制代码

samuel1004

刚没看到3楼的 呵呵 谢谢了

samuel1004

原帖由 zx_wing 于 2007-4-17 15:51 发表


以后遇到系统调用的问题，应该先请教man，再发到论坛上来。不能偷懒，不然别人不会给回复。
[code]
alarm arranges for a SIGALRM signal to be delivered to the process in seconds seconds.

If seco ...

刚开始学，还没习惯用man，以后多注意了。。