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