src/unix/snglinst.cpp

   1 ///////////////////////////////////////////////////////////////////////////////
   2 // Name:        src/unix/snglinst.cpp
   3 // Purpose:     implements wxSingleInstanceChecker class for Unix using
   4 //              lock files with fcntl(2) or flock(2)
   5 // Author:      Vadim Zeitlin
   6 // Modified by:
   7 // Created:     09.06.01
   8 // RCS-ID:      $Id$
   9 // Copyright:   (c) 2001 Vadim Zeitlin <zeitlin@dptmaths.ens-cachan.fr>
  10 // License:     wxWindows licence
  11 ///////////////////////////////////////////////////////////////////////////////
  12
  13 // ============================================================================
  14 // declarations
  15 // ============================================================================
  16
  17 // ----------------------------------------------------------------------------
  18 // headers
  19 // ----------------------------------------------------------------------------
  20
  21 // For compilers that support precompilation, includes "wx.h".
  22 #include "wx/wxprec.h"
  23
  24 #ifdef __BORLANDC__
  25     #pragma hdrstop
  26 #endif
  27
  28 #if wxUSE_SNGLINST_CHECKER
  29
  30 #ifndef WX_PRECOMP
  31     #include "wx/string.h"
  32     #include "wx/log.h"
  33     #include "wx/intl.h"
  34     #include "wx/utils.h"           // wxGetHomeDir()
  35 #endif //WX_PRECOMP
  36
  37 #include "wx/file.h"
  38
  39 #include "wx/snglinst.h"
  40
  41 #include <unistd.h>
  42 #include <sys/types.h>
  43 #include <sys/stat.h>           // for S_I[RW]USR
  44 #include <signal.h>             // for kill()
  45 #include <errno.h>
  46
  47 #ifdef HAVE_FCNTL
  48     #include <fcntl.h>
  49 #elif defined(HAVE_FLOCK)
  50     #include <sys/file.h>
  51 #else
  52     // normally, wxUSE_SNGLINST_CHECKER must have been reset by configure
  53     #error "wxSingleInstanceChecker can't be compiled on this platform"
  54 #endif // fcntl()/flock()
  55
  56 // ----------------------------------------------------------------------------
  57 // constants
  58 // ----------------------------------------------------------------------------
  59
  60 // argument of wxLockFile()
  61 enum LockOperation
  62 {
  63     LOCK,
  64     UNLOCK
  65 };
  66
  67 // return value of CreateLockFile()
  68 enum LockResult
  69 {
  70     LOCK_ERROR = -1,
  71     LOCK_EXISTS,
  72     LOCK_CREATED
  73 };
  74
  75 // ----------------------------------------------------------------------------
  76 // private functions: (exclusively) lock/unlock the file
  77 // ----------------------------------------------------------------------------
  78
  79 #ifdef HAVE_FCNTL
  80
  81 static int wxLockFile(int fd, LockOperation lock)
  82 {
  83     // init the flock parameter struct
  84     struct flock fl;
  85     fl.l_type = lock == LOCK ? F_WRLCK : F_UNLCK;
  86
  87     // lock the entire file
  88     fl.l_start =
  89     fl.l_len =
  90     fl.l_whence = 0;
  91
  92     // is this needed?
  93     fl.l_pid = getpid();
  94
  95     return fcntl(fd, F_SETLK, &fl);
  96 }
  97
  98 #else // HAVE_FLOCK
  99
 100 static int wxLockFile(int fd, LockOperation lock)
 101 {
 102     return flock(fd, lock == LOCK ? LOCK_EX | LOCK_NB : LOCK_UN);
 103 }
 104
 105 #endif // fcntl()/flock()
 106
 107 // ----------------------------------------------------------------------------
 108 // wxSingleInstanceCheckerImpl: the real implementation class
 109 // ----------------------------------------------------------------------------
 110
 111 class wxSingleInstanceCheckerImpl
 112 {
 113 public:
 114     wxSingleInstanceCheckerImpl()
 115     {
 116         m_fdLock = -1;
 117         m_pidLocker = 0;
 118     }
 119
 120     bool Create(const wxString& name);
 121
 122     pid_t GetLockerPID() const { return m_pidLocker; }
 123
 124     ~wxSingleInstanceCheckerImpl() { Unlock(); }
 125
 126 private:
 127     // try to create and lock the file
 128     LockResult CreateLockFile();
 129
 130     // unlock and remove the lock file
 131     void Unlock();
 132
 133     // the descriptor of our lock file, -1 if none
 134     int m_fdLock;
 135
 136     // pid of the process owning the lock file
 137     pid_t m_pidLocker;
 138
 139     // the name of the lock file
 140     wxString m_nameLock;
 141 };
 142
 143 // ============================================================================
 144 // wxSingleInstanceCheckerImpl implementation
 145 // ============================================================================
 146
 147 LockResult wxSingleInstanceCheckerImpl::CreateLockFile()
 148 {
 149     // try to open the file
 150     m_fdLock = open(m_nameLock.fn_str(),
 151                     O_WRONLY | O_CREAT | O_EXCL,
 152                     S_IRUSR | S_IWUSR);
 153
 154     if ( m_fdLock != -1 )
 155     {
 156         // try to lock it
 157         if ( wxLockFile(m_fdLock, LOCK) == 0 )
 158         {
 159             // fine, we have the exclusive lock to the file, write our PID
 160             // into it
 161             m_pidLocker = getpid();
 162
 163             // use char here, not wxChar!
 164             char buf[256]; // enough for any PID size
 165             int len = sprintf(buf, "%d", (int)m_pidLocker) + 1;
 166
 167             if ( write(m_fdLock, buf, len) != len )
 168             {
 169                 wxLogSysError(_("Failed to write to lock file '%s'"),
 170                               m_nameLock.c_str());
 171
 172                 Unlock();
 173
 174                 return LOCK_ERROR;
 175             }
 176
 177             fsync(m_fdLock);
 178
 179             // change file's permission so that only this user can access it:
 180             if ( chmod(m_nameLock.fn_str(), S_IRUSR | S_IWUSR) != 0 )
 181             {
 182                 wxLogSysError(_("Failed to set permissions on lock file '%s'"),
 183                               m_nameLock.c_str());
 184
 185                 Unlock();
 186
 187                 return LOCK_ERROR;
 188             }
 189
 190             return LOCK_CREATED;
 191         }
 192         else // failure: see what exactly happened
 193         {
 194             close(m_fdLock);
 195             m_fdLock = -1;
 196
 197             if ( errno != EACCES && errno != EAGAIN )
 198             {
 199                 wxLogSysError(_("Failed to lock the lock file '%s'"),
 200                               m_nameLock.c_str());
 201
 202                 unlink(m_nameLock.fn_str());
 203
 204                 return LOCK_ERROR;
 205             }
 206             //else: couldn't lock because the lock is held by another process:
 207             //      this might have happened because of a race condition:
 208             //      maybe another instance opened and locked the file between
 209             //      our calls to open() and flock(), so don't give an error
 210         }
 211     }
 212
 213     // we didn't create and lock the file
 214     return LOCK_EXISTS;
 215 }
 216
 217 bool wxSingleInstanceCheckerImpl::Create(const wxString& name)
 218 {
 219     m_nameLock = name;
 220
 221     switch ( CreateLockFile() )
 222     {
 223         case LOCK_EXISTS:
 224             // there is a lock file, check below if it is still valid
 225             break;
 226
 227         case LOCK_CREATED:
 228             // nothing more to do
 229             return true;
 230
 231         case LOCK_ERROR:
 232             // oops...
 233             return false;
 234     }
 235
 236     // Check if the file is owned by current user and has 0600 permissions.
 237     // If it doesn't, it's a fake file, possibly meant as a DoS attack, and
 238     // so we refuse to touch it:
 239     wxStructStat stats;
 240     if ( wxStat(name, &stats) != 0 )
 241     {
 242         wxLogSysError(_("Failed to inspect the lock file '%s'"), name.c_str());
 243         return false;
 244     }
 245     if ( stats.st_uid != getuid() )
 246     {
 247         wxLogError(_("Lock file '%s' has incorrect owner."), name.c_str());
 248         return false;
 249     }
 250     if ( stats.st_mode != (S_IFREG | S_IRUSR | S_IWUSR) )
 251     {
 252         wxLogError(_("Lock file '%s' has incorrect permissions."), name.c_str());
 253         return false;
 254     }
 255
 256     // try to open the file for reading and get the PID of the process
 257     // which has it
 258     wxFile file(name, wxFile::read);
 259     if ( !file.IsOpened() )
 260     {
 261         // well, this is really weird - file doesn't exist and we can't
 262         // create it
 263         //
 264         // normally, this just means that we don't have write access to
 265         // the directory where we try to create it, so return failure,
 266         // even it might also be a rare case of a race condition when
 267         // another process managed to open and lock the file and terminate
 268         // (erasing it) before we got here, but this should happen so
 269         // rarely in practice that we don't care
 270         wxLogError(_("Failed to access lock file."));
 271
 272         return false;
 273     }
 274
 275     char buf[256];
 276     ssize_t count = file.Read(buf, WXSIZEOF(buf));
 277     if ( count == wxInvalidOffset )
 278     {
 279         wxLogError(_("Failed to read PID from lock file."));
 280     }
 281     else
 282     {
 283         if ( sscanf(buf, "%d", (int *)&m_pidLocker) == 1 )
 284         {
 285             if ( kill(m_pidLocker, 0) != 0 )
 286             {
 287                 if ( unlink(name.fn_str()) != 0 )
 288                 {
 289                     wxLogError(_("Failed to remove stale lock file '%s'."),
 290                                name.c_str());
 291
 292                     // return true in this case for now...
 293                 }
 294                 else
 295                 {
 296                     wxLogMessage(_("Deleted stale lock file '%s'."),
 297                                  name.c_str());
 298
 299                     // retry now
 300                     (void)CreateLockFile();
 301                 }
 302             }
 303             //else: the other process is running
 304         }
 305         else
 306         {
 307             wxLogWarning(_("Invalid lock file '%s'."), name.c_str());
 308         }
 309     }
 310
 311     // return true if we could get the PID of the process owning the lock file
 312     // (whether it is still running or not), FALSE otherwise as it is
 313     // unexpected
 314     return m_pidLocker != 0;
 315 }
 316
 317 void wxSingleInstanceCheckerImpl::Unlock()
 318 {
 319     if ( m_fdLock != -1 )
 320     {
 321         if ( unlink(m_nameLock.fn_str()) != 0 )
 322         {
 323             wxLogSysError(_("Failed to remove lock file '%s'"),
 324                           m_nameLock.c_str());
 325         }
 326
 327         if ( wxLockFile(m_fdLock, UNLOCK) != 0 )
 328         {
 329             wxLogSysError(_("Failed to unlock lock file '%s'"),
 330                           m_nameLock.c_str());
 331         }
 332
 333         if ( close(m_fdLock) != 0 )
 334         {
 335             wxLogSysError(_("Failed to close lock file '%s'"),
 336                           m_nameLock.c_str());
 337         }
 338     }
 339
 340     m_pidLocker = 0;
 341 }
 342
 343 // ============================================================================
 344 // wxSingleInstanceChecker implementation
 345 // ============================================================================
 346
 347 bool wxSingleInstanceChecker::Create(const wxString& name,
 348                                      const wxString& path)
 349 {
 350     wxASSERT_MSG( !m_impl,
 351                   _T("calling wxSingleInstanceChecker::Create() twice?") );
 352
 353     // must have the file name to create a lock file
 354     wxASSERT_MSG( !name.empty(), _T("lock file name can't be empty") );
 355
 356     m_impl = new wxSingleInstanceCheckerImpl;
 357
 358     wxString fullname = path;
 359     if ( fullname.empty() )
 360     {
 361         fullname = wxGetHomeDir();
 362     }
 363
 364     if ( fullname.Last() != _T('/') )
 365     {
 366         fullname += _T('/');
 367     }
 368
 369     fullname << name;
 370
 371     return m_impl->Create(fullname);
 372 }
 373
 374 bool wxSingleInstanceChecker::IsAnotherRunning() const
 375 {
 376     wxCHECK_MSG( m_impl, false, _T("must call Create() first") );
 377
 378     const pid_t lockerPid = m_impl->GetLockerPID();
 379
 380     if ( !lockerPid )
 381     {
 382         // we failed to open the lock file, return false as we're definitely
 383         // not sure that another our process is running and so it's better not
 384         // to prevent this one from starting up
 385         return false;
 386     }
 387
 388     // if another instance is running, it must own the lock file - otherwise
 389     // we have it and the locker PID is ours one
 390     return lockerPid != getpid();
 391 }
 392
 393 wxSingleInstanceChecker::~wxSingleInstanceChecker()
 394 {
 395     delete m_impl;
 396 }
 397
 398 #endif // wxUSE_SNGLINST_CHECKER