信号完结

C16-并发/parallel/signal/mydaemon.c

@@ -0,0 +1,112 @@
+#include <errno.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/syslog.h>
+#include <syslog.h>
+#include <time.h>
+#include <unistd.h>
+
+#define FNAME "/tmp/out"
+
+static FILE* fp;
+
+static int deamonize(void)
+{
+    pid_t pid;
+    int   fd;
+
+    pid = fork( );
+    if (pid < 0)
+        return -1;
+
+    if (pid > 0)   // parent process
+        exit(0);
+
+    fd = open("/dev/null", O_RDWR);
+    if (fd < 0)
+        return -1;
+
+    dup2(fd, 0);
+    dup2(fd, 1);
+    dup2(fd, 2);
+    if (fd > 2)
+        close(fd);
+
+    setsid( );
+
+    chdir("/");   // 防止一直占用某设备
+    // umask(0);
+
+    return 0;
+}
+
+static void daemon_exit(int s)
+{
+    // if(SIGINT == s) 可以进行区分处理
+
+    fclose(fp);   // 当多个信号响应同一个函数，可能多次free
+    closelog( );
+    exit(0);
+}
+
+int main(int argc, char** argv)
+{
+    int              i;
+    struct sigaction sa;
+
+    sa.sa_handler = daemon_exit;
+    sigemptyset(&sa.sa_mask);
+    sigaddset(&sa.sa_mask, SIGQUIT);
+    sigaddset(&sa.sa_mask, SIGTERM);
+    sigaddset(&sa.sa_mask, SIGINT);
+    sa.sa_flags = 0;
+    // !! 为了防止重入，对其中一个信号注册时要阻塞另外两个信号
+    // 干脆就三个一起阻塞
+
+    sigaction(SIGINT, &sa, NULL);
+    sigaction(SIGQUIT, &sa, NULL);
+    sigaction(SIGTERM, &sa, NULL);
+
+    // signal(SIGINT, daemon_exit);
+    // signal(SIGQUIT, daemon_exit);
+    // signal(SIGTERM, daemon_exit);
+
+    openlog("mydaemon", LOG_PID, LOG_DAEMON);
+
+    if (deamonize( ))
+    {
+        syslog(LOG_ERR, "daemonize() failed!");
+        exit(1);
+    }
+    else
+    {
+        syslog(LOG_INFO, "daemonize() success!");
+    }
+
+    fp = fopen(FNAME, "w");
+    if (fp == NULL)
+    {
+        syslog(LOG_ERR, "fopen() failed!: %s", strerror(errno));
+        exit(1);
+    }
+
+    syslog(LOG_INFO, "%s was opened successfully!", FNAME);
+
+    for (i = 0;; i++)
+    {
+        fprintf(fp, "%d\n", i);
+        fflush(fp);   //! 刷新缓冲区
+        syslog(LOG_DEBUG, "%d is printed", i);
+        sleep(1);
+    }
+
+    // 目前守护进程只能异常终止，下面其实无法执行到
+    // fclose(fp);
+    // closelog( );
+
+    exit(0);
+}