分享Linux实例进程代码

mytomorrow · 发表于 2019-9-19 11:31

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Linux实例进程代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <syslog.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>

#define LOCKFILE "/var/run/mydaemon.pid"
#define LOCKMODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH)

int lockfile(int fd)
{
      struct flock fl;

      fl.l_type = F_WRLCK;
      fl.l_start = 0;
      fl.l_whence = SEEK_SET;
      fl.l_len = 0;

      return(fcntl(fd, F_SETLK, &fl));
}

int already_running(const char *filename)
{
      int fd;
      char buf[16];

      fd = open(filename, O_RDWR | O_CREAT, LOCKMODE);
      if (fd < 0) {
            syslog(LOG_ERR, "can't open %s: %m\n", filename);
            exit(1);
      }
      if (lockfile(fd) == -1) {
            if (errno == EACCES || errno == EAGAIN) {
                     syslog(LOG_ERR, "file: %s already locked", filename);
                     close(fd);
                     return 1;
            }
            syslog(LOG_ERR, "can't lock %s: %m\n", filename);
            exit(1);
      }
      ftruncate(fd, 0);
      sprintf(buf, "%ld", (long)getpid());
      write(fd, buf, strlen(buf) + 1);
      return 0;
}

int main(int argc, char *argv[])
{
      if (already_running(LOCKFILE))
            return 0;

      printf("start main...\n");
      sleep(100);
      printf("main done!\n");

      exit(0);
}

Demyar · 发表于 2019-9-19 18:08

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分享Linux实例进程代码

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