src/unix/snglinst.cpp

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