OW_PidFile.cpp

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#include "OW_config.h"
#include "OW_PidFile.hpp"
#include "OW_File.hpp"
#include "OW_FileSystem.hpp"
#include "OW_String.hpp"

#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <signal.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>


namespace OW_NAMESPACE
{

namespace PidFile
{
int 
readPid(const char *pidfile)
{
   FILE *f;
   int pid = -1;
   if (!(f = fopen(pidfile,"r")))
      return -1;
   fscanf(f,"%d", &pid);
   fclose(f);
   return pid;
}
int 
checkPid(const char *pidfile)
{
   int pid = readPid(pidfile);
   // Amazing ! _I_ am already holding the pid file...
   if ((!pid) || (pid == getpid()))
      return -1;
   // Check if the process exists
   if (kill(pid, 0) && errno == ESRCH)
      return -1;
   return pid;
}
int 
writePid(const char *pidfile)
{
   FILE *f;
   int fd;
   int pid;
   int lerrno;
   if ((fd = open(pidfile, O_RDWR|O_CREAT, 0644)) == -1)
   {
      return -1;
   }
   if ((f = fdopen(fd, "r+")) == NULL)
   {
      lerrno = errno;
      close(fd);
      errno = lerrno;
      return -1;
   }
   File OWf(::dup(fd)); // need a dup, since the FILE* will close it.
   if (OWf.tryLock() == -1)
   {
      lerrno = errno;
      fscanf(f, "%d", &pid);
      fclose(f);
      errno = lerrno;
      return -1;
   }
   pid = getpid();
   if (!fprintf(f,"%d\n", pid))
   {
      lerrno = errno;
      fclose(f);
      errno = lerrno;
      return -1;
   }
   fflush(f);
   OWf.unlock();
   fclose(f);
   return pid;
}
int 
removePid(const char *pidfile)
{
   return FileSystem::removeFile(pidfile);
}

} // end namespace PidFile
} // end namespace OW_NAMESPACE

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