===============================================================================
#include <sys/types.h>
#include <signal.h>
int kill (pid_t pid, int sig);
int raise (int sig);
-------------------------------------------------------------------------------
kill 的 pid 参数的四种条件:
* pid > 0: 信号发送到 PID 为 pid 的进程.
* pid == 0: 信号发送到与发送进程处于同一进程组的进程.
* pid < -1: 信号发送到进程组 ID 等于 -pid 的所有进程.
* pid == -1: POSIX 未指定. Linux 发送到进程表中所有的进程, 除第一个进程之外.
* sig == 0 时, 不会发送任何信号, 但仍然执行错误检查, 因此可用来检查是否有
向指定进程发送信号的许可.
===============================================================================
===============================================================================
#include <unistd.h>
unsigned int alarm (unsigned int seconds);
-------------------------------------------------------------------------------
#include <sys/time.h>
int getitimer (int which, struct itimerval *value);
int setitimer (int which, const struct itimerval *value, struct itimerval *ovalue);
-------------------------------------------------------------------------------
* alarm 的返回值为先前尚未过期的定时器所剩余的时间.
* alarm 和 setitimer 使用同一个定时器, 因此会互相影响.
* setitimer 定时精度要比 alarm 高, 同时可以按照进程的执行时间 (用户态时间,
核心态时间, 或两者) 进行计时.
-------------------------------------------------------------------------------
EXAMPLE:
/* MiniGUI 的定时器 */
void sig_handler (int v)
{
int sem_value;
timer_counter++;
// alert desktop
DskMsgs.dwState |= 0x01;
sem_getvalue (&DskMsgs.wait, &sem_value);
if (sem_value == 0)
sem_post(&DskMsgs.wait);
}
BOOL InitTimer ()
{
struct itimerval timerv;
struct sigaction siga;
siga.sa_handler = sig_handler;
siga.sa_flags = 0;
memset (&siga.sa_mask, 0, sizeof (sigset_t));
sigaction (SIGALRM, &siga, &old_alarm_handler);
timerv.it_interval.tv_sec = 0;
timerv.it_interval.tv_usec = 10000;
timerv.it_value = timerv.it_interval;
if (setitimer (ITIMER_REAL, &timerv, &old_timer)) {
fprintf(stderr, "TIMER: setitimer call failed!\n");
perror("setitimer");
return FALSE;
}
timer_counter = 0;
return TRUE;
}
BOOL TerminateTimer ()
{
int i;
if (setitimer (ITIMER_REAL, &old_timer, 0) == -1) {
fprintf( stderr, "Timer: setitimer call failed!\n");
perror("setitimer");
return 0;
}
if (sigaction (SIGALRM, &old_alarm_handler, NULL) == -1) {
fprintf( stderr, "Timer: sigaction call failed!\n");
perror("sigaction");
return 0;
}
for (i=0; i < MAX_TIMERS; i++) {
if (timerstr[i] != NULL)
free ( timerstr[i] );
timerstr[i] = NULL;
}
return 1;
}
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===============================================================================
#include <unistd.h>
int pause (void);
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===============================================================================
#include <stdlib.h>
void abort (void);
-------------------------------------------------------------------------------
* 如果捕获 SIGABRT 信号, 且信号处理器不返回, 则 abort 不能终止进程.
* abort 终止进程时, 所有打开的流均会被刷新并关闭.
* 如果 SIGABRT 被阻塞或忽略, abort 将覆盖这种设置.
===============================================================================
===============================================================================
#include <stdlib.h>
int system (const char * string);
-------------------------------------------------------------------------------
* 在执行命令的过程中, SIGCHLD 被阻塞, 而 SIGINT 和 SIGQUIT 被忽略.
-------------------------------------------------------------------------------
EXAMPLE:
/* POSIX.2 implementation of system function */
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <signal.h>
#include <unistd.h>
int system (const char *cmdstring) /* with appropriate signal handling */
{
pid_t pid;
int status;
struct sigaction ignore, saveintr, savequit;
sigset_t childmask, savemask;
if (cmdstring == NULL)
return (1); /* always a command processor with UNIX */
ignore.sa_handler = SIG_IGN; /* ignore SIGINT and SIGQUIT */
sigemptyset (&ignore.sa_mask);
ignore.sa_flags = 0;
if (sigaction (SIGINT, &ignore, &saveintr) < 0)
return (-1);
if (sigaction (SIGQUIT, &ignore, &savequit) < 0)
return (-1);
sigemptyset (&childmask); /* now block SIGCHLD */
sigaddset (&childmask, SIGCHLD);
if (sigprocmask (SIG_BLOCK, &childmask, &savemask) < 0)
return (-1);
if ( (pid = fork ()) < 0) {
status = -1; /* probably out of processes */
}
else if (pid == 0) { /* child */
/* restore previous signal actions & rest signal mask */
sigaction (SIGINT, &saveintr, NULL);
sigaction (SIGQUIT, &savequit, NULL);
sigprocmask (SIG_SETMASK, &savemask, NULL);
execl ("/bin/sh", "sh", "-c", cmdstring, (char *)0);
_exit (127); /* exec error */
}
else { /* parent */
while (waitpid (pid, &status, 0) < 0)
if (errno != EINTR) {
status = -1; /* errno other than EINTR form waitpid() */
break;
}
}
/* restore previous signal actions & reset signal mask */
if (sigaction (SIGINT, &saveintr, NULL) < 0)
return (-1);
if (sigaction (SIGQUIT, &savequit, NULL) < 0)
return (-1);
if (sigprocmask (SIG_SETMASK, &savemask, NULL) == 0)
return (-1);
return (status);
}
===============================================================================
===============================================================================
#include <unistd.h>
unsigned int sleep (unsigned int seconds);
-------------------------------------------------------------------------------
* 经过指定的时间之后, sleep 返回.
* 在这之前, 如果接收到信号, 则 sleep 返回剩余的秒数.
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
EXAMPLE:
/* POSIX.2 implementation of sleep function */
#include <sys/types.h>
#include <stddef.h>
#include <signal.h>
#include <unistd.h>
static void sig_alrm (void)
{
return; /* nothing to do, just returning wakes up sigsuspend() */
}
unsigned int sleep (unsigned int nsecs)
{
struct sigaction newact, oldact;
sigset_t newmask, oldmask, suspmask;
unsigned int unslept;
newact.sa_handler = sig_alrm;
sigemptyset (&newact.sa_mask);
newact.sa_flags = 0;
sigaction (SIGALRM, &newact, &oldact);
/* set our handler, save previous information */
sigemptyset (&newmask);
sigaddset (&newmask, SIGALRM);
/* block SIGALRM and save current signal mask */
sigprocmask (SIG_BLOCK, &newmask, &oldmask);
alarm (nsecs);
suspmask = oldmask;
sigdelset (&suspmask, SIGALRM); /* make sure SIGALRM isn't blocked */
sigsuspend (&suspmask); /* wait for any signal to be caught */
/* some signal has been caught, SIGALRM is now blocked */
unslept = alarm (0);
sigaction (SIGALRM, &oldact, NULL); /* reset previous action */
sigprocmask (SIG_SETMASK, &oldmask, NULL);
return (unslept);
}
===============================================================================
