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pidfile.c

/* this code is broken - there is a race condition with the unlink (tridge) */

/* 
   Unix SMB/Netbios implementation.
   Version 1.9.
   pidfile handling
   Copyright (C) Andrew Tridgell 1998
   
   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.
   
   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.
   
   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/

#include "includes.h"


#ifndef O_NONBLOCK
#ifdef SYSV
#define O_NONBLOCK O_NDELAY
#else
#define O_NONBLOCK FNDELAY
#endif
#endif

/* return the pid in a pidfile. return 0 if the process (or pidfile)
   does not exist */
pid_t pidfile_pid(const char *name)
{
      int fd;
      char pidstr[20];
      unsigned ret;
      pstring pidFile;

      slprintf(pidFile, sizeof(pidFile)-1, "%s/%s.pid", lp_piddir(), name);

      fd = sys_open(pidFile, O_NONBLOCK | O_RDONLY, 0644);
      if (fd == -1) {
            return 0;
      }

      ZERO_ARRAY(pidstr);

      if (read(fd, pidstr, sizeof(pidstr)-1) <= 0) {
            goto noproc;
      }

      ret = atoi(pidstr);
      
      if (!process_exists((pid_t)ret)) {
            goto noproc;
      }

      if (fcntl_lock(fd,SMB_F_SETLK,0,1,F_RDLCK)) {
            /* we could get the lock - it can't be a Samba process */
            goto noproc;
      }

      close(fd);
      return (pid_t)ret;

 noproc:
      close(fd);
      unlink(pidFile);
      return 0;
}

/* create a pid file in the pid directory. open it and leave it locked */
void pidfile_create(const char *name)
{
      int     fd;
      char    buf[20];
      pstring pidFile;
      pid_t pid;

      slprintf(pidFile, sizeof(pidFile)-1, "%s/%s.pid", lp_piddir(), name);

      pid = pidfile_pid(name);
      if (pid != 0) {
            DEBUG(0,("ERROR: %s is already running. File %s exists and process id %d is running.\n", 
                   name, pidFile, (int)pid));
            exit(1);
      }

      fd = sys_open(pidFile, O_NONBLOCK | O_CREAT | O_WRONLY | O_EXCL, 0644);
      if (fd == -1) {
            DEBUG(0,("ERROR: can't open %s: Error was %s\n", pidFile, 
                   strerror(errno)));
            exit(1);
      }

      if (fcntl_lock(fd,SMB_F_SETLK,0,1,F_WRLCK)==False) {
            DEBUG(0,("ERROR: %s : fcntl lock of file %s failed. Error was %s\n",  
              name, pidFile, strerror(errno)));
            exit(1);
      }

      memset(buf, 0, sizeof(buf));
      slprintf(buf, sizeof(buf) - 1, "%u\n", (unsigned int) sys_getpid());
      if (write(fd, buf, sizeof(buf)) != sizeof(buf)) {
            DEBUG(0,("ERROR: can't write to file %s: %s\n", 
                   pidFile, strerror(errno)));
            exit(1);
      }
      /* Leave pid file open & locked for the duration... */
}

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