lpudated-sig.c

基于网络编程的例子

/*
 * lpudated-sig.c - Simple timestamping daemon that reads a 
 *                  config file in /etc and handles signals
 */
#include <sys/types.h>
#include <sys/stat.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <time.h>
#include <syslog.h>
#include <signal.h>

#define RCFILE "/etc/lpudated.conf" /* The config file */
#define BUFLEN 256 /* Length of buffer reads */
#define NORMAL 1
#define ROT13 2

/* Read the config file */
int read_config(int rcfd, int *o_style);

int main(void)
{
    pid_t pid, sid;
    time_t timebuf;
    int rcfd, fd, len, o_style;

    pid = fork();
    if(pid < 0) {
        syslog(LOG_ERR, "%s\n", perror);
        exit(EXIT_FAILURE);
    }
    if(pid > 0) 
        exit(EXIT_SUCCESS);

   openlog("lpudated", LOG_PID, LOG_DAEMON);

    /* Read the config file */
    if((rcfd = open(RCFILE, O_RDONLY)) < 0) {
        syslog(LOG_ERR, "error opening %s\n", RCFILE);
        exit(EXIT_FAILURE);
    } else {
        if((read_config(rcfd, &o_style)) < 0) {
            syslog(LOG_ERR, "error raading %s\n", RCFILE);
            exit(EXIT_FAILURE);
        }

        if(close(rcfd) < 0) {
           syslog(LOG_ERR, "error closing %s\n", RCFILE);
           exit(EXIT_FAILURE);
        }
    }

    /* First, start a new session */
    if((sid = setsid()) < 0) {
        syslog(LOG_ERR, "%s\n", "setsid");
        exit(EXIT_FAILURE);
    }

    /* Next, make / the current directory */
    if((chdir("/")) < 0) {
        syslog(LOG_ERR, "%s\n", "chdir");
        exit(EXIT_FAILURE);
    }

    /* Reset the file mode */
    umask(0);

    /* Close unneeded file descriptors */
    close(STDIN_FILENO);
    close(STDOUT_FILENO);
    close(STDERR_FILENO);

    /*  Finally, do our work */
    len = strlen(ctime(&timebuf));
    while(1) {
        char *buf = malloc(sizeof(char) * (len + 1));
        sigset_t sigset;	
        struct sigaction action;
        int i;

        if(buf == NULL) {
            syslog(LOG_ERR, "malloc");
            exit(EXIT_FAILURE);
        }
        if((fd = open("/var/log/lpudated.log",
                       O_CREAT | O_WRONLY | O_APPEND, 0600)) < 0) {
            syslog(LOG_ERR, "open");
            exit(EXIT_FAILURE);
        }

        sigemptyset(&sigset); /* Initialize signal set */
        sigaddset(&sigset, SIGHUP); /* Add SIGHUP to it */
        sigprocmask(SIG_BLOCK, &sigset, NULL); /* Block SIGHUP */
	
        time(&timebuf);
        strncpy(buf, ctime(&timebuf), len + 1);
        if(o_style == ROT13) {
            for(i = 0; i <= len; ++i)
                if((buf[i] >= 'A' && buf[i] <= 'M') ||
                   (buf[i] >= 'a' && buf[i] <= 'm'))
                    buf[i] += 13;
                else if((buf[i] >= 'N' && buf[i] <= 'Z') ||
                        (buf[i] >= 'n' && buf[i] <= 'z'))
                    buf[i] -= 13;
        }
        write(fd, buf, len + 1);
        close(fd);
		
        sigpending(&sigset); /* Check for pending signals */
        if(sigismember(&sigset, SIGHUP)) {
            syslog(LOG_INFO, "received SIGHUP\n");
            /* Ignore SIGHUP */
            sigemptyset(&action.sa_mask);
            action.sa_handler = SIG_IGN;
            sigaction(SIGHUP, &action, NULL);
            /* Reread the configuration file */
            if((rcfd = open(RCFILE, O_RDONLY)) < 0) {
                syslog(LOG_ERR, "error opening %s\n", RCFILE);
                exit(EXIT_FAILURE);
            } else {
                if((read_config(rcfd, &o_style)) < 0) {
                    syslog(LOG_ERR, "error raading %s\n", RCFILE);
                    exit(EXIT_FAILURE);
                }
                if(close(rcfd) < 0) {
                    syslog(LOG_ERR, "error closing %s\n", RCFILE);
                    exit(EXIT_FAILURE);
                }
            }
            /* Unblock SIGHUP */
            sigprocmask(SIG_UNBLOCK, &sigset, NULL);
        }
        sleep(60);
    }
    /* Close the system log and scram */
    closelog();
    exit(EXIT_SUCCESS);
}

int read_config(int rcfd, int *o_style)
{
    char rcbuf[BUFLEN]; /* Hold the value read */
    int len; /* The length of the buffer */
	
    /* Read the config file */
    if((len = read(rcfd, rcbuf, BUFLEN)) < 0) {
        syslog(LOG_ERR, "error reading %s\n", RCFILE);
        return 1;
    }
    rcbuf[len] = '\0';
	
    /* Determine what we read */
    if(0 == strncmp(rcbuf, "rot13", 5)) { /* Want rot13 output */
        *o_style = ROT13;
        syslog(LOG_INFO, "output style is rot13\n");
    } else if(0 == strncmp(rcbuf, "normal", 6)) { /* Want normal output */
        *o_style = NORMAL;
	syslog(LOG_INFO, "output style is normal\n");
    } else { /* Invalid value in config file */
        syslog(LOG_ERR, "invalid output style %d\n", *o_style);
        return 2;
    }
   	 
    return 0;
}