TSystem

class TSystem : public TNamed

    protected:

           virtual Bool_t ConsistentWith(const char* path, void* dirptr = 0)
      virtual const char* ExpandFileName(const char* fname) const
                 TSystem* FindHelper(const char* path, void* dirptr = 0)
      virtual const char* GetLinkedLibraries() const
             virtual void SigAlarmInterruptsSyscalls(Bool_t)

    public:

                                  TSystem(const char* name = "Generic", const char* title = "Generic System")
                                  TSystem(const TSystem&)
                          virtual ~TSystem()
                     virtual void Abort(int code = 0)
                      virtual int AcceptConnection(int sock)
                   virtual Bool_t AccessPathName(const char* path, EAccessMode mode = kFileExists)
                     virtual void AddFileHandler(TFileHandler* fh)
                     virtual void AddIncludePath(const char* includePath)
                     virtual void AddLinkedLibs(const char* linkedLib)
                     virtual void AddSignalHandler(TSignalHandler* sh)
                     virtual void AddTimer(TTimer* t)
                      virtual int AnnounceTcpService(int port, Bool_t reuse, int backlog, int tcpwindowsize = -1)
                      virtual int AnnounceUnixService(int port, int backlog)
              virtual const char* BaseName(const char* pathname) const
                           Bool_t cd(const char* path)
                   virtual Bool_t ChangeDirectory(const char* path)
                      virtual int Chmod(const char* file, UInt_t mode)
                   static TClass* Class()
                     virtual void CleanCompiledMacros()
                     virtual void CloseConnection(int sock, Bool_t force = kFALSE)
                     virtual void Closelog()
                      virtual int ClosePipe(FILE* pipe)
                      virtual int CompileMacro(const char* filename, Option_t* opt = "", const char* library_name = "", const char* build_dir = "")
                    virtual char* ConcatFileName(const char* dir, const char* name)
                      virtual int CopyFile(const char* from, const char* to, Bool_t overwrite = kFALSE)
              virtual const char* DirName(const char* pathname) const
                     virtual void DispatchOneEvent(Bool_t pendingOnly = kFALSE)
                    virtual char* DynamicPathName(const char* lib, Bool_t quiet = kFALSE)
                   virtual Func_t DynFindSymbol(const char* module, const char* entry)
                    virtual Int_t Exec(const char* shellcmd)
                     virtual void Exit(int code, Bool_t mode = kTRUE)
                     virtual void ExitLoop()
                   virtual Bool_t ExpandPathName(TString& path)
                    virtual char* ExpandPathName(const char* path)
                     virtual void FreeDirectory(void* dirp)
      virtual TSystem::EAclicMode GetAclicMode() const
              virtual const char* GetBuildArch() const
              virtual const char* GetBuildDir() const
              virtual const char* GetBuildNode() const
              virtual const char* GetDirEntry(void* dirp) const
                    virtual void* GetDirPtr() const
              virtual const char* GetDynamicPath() const
                    virtual Int_t GetEffectiveGid()
                    virtual Int_t GetEffectiveUid()
              virtual const char* Getenv(const char* env) const
                     static Int_t GetErrno()
              virtual const char* GetError() const
                      const char* GetErrorStr() const
              virtual const char* GetFlagsDebug() const
              virtual const char* GetFlagsOpt() const
                    virtual Int_t GetFPEMask()
                      virtual int GetFsInfo(const char* path, Long_t* id, Long_t* bsize, Long_t* blocks, Long_t* bfree)
                    virtual Int_t GetGid(const char* group = "0")
             virtual UserGroup_t* GetGroupInfo(Int_t gid)
             virtual UserGroup_t* GetGroupInfo(const char* group = "0")
             virtual TInetAddress GetHostByName(const char* server)
              virtual const char* GetIncludePath() const
              virtual const char* GetLibraries(const char* regexp = "", const char* option = "", Bool_t isRegexp = kTRUE) const
              virtual const char* GetLinkdefSuffix() const
              virtual const char* GetLinkedLibs() const
          virtual TSeqCollection* GetListOfFileHandlers() const
              virtual const char* GetMakeExe() const
              virtual const char* GetMakeSharedLib() const
              virtual const char* GetObjExt() const
                              int GetPathInfo(const char* path, Long_t* id, Long_t* size, Long_t* flags, Long_t* modtime)
                              int GetPathInfo(const char* path, Long_t* id, Long64_t* size, Long_t* flags, Long_t* modtime)
                      virtual int GetPathInfo(const char* path, FileStat_t& buf)
             virtual TInetAddress GetPeerName(int sock)
                      virtual int GetPid()
                      virtual int GetServiceByName(const char* service)
                    virtual char* GetServiceByPort(int port)
             virtual TInetAddress GetSockName(int sock)
                      virtual int GetSockOpt(int sock, int kind, int* val)
              virtual const char* GetSoExt() const
                    virtual Int_t GetUid(const char* user = "0")
             virtual UserGroup_t* GetUserInfo(Int_t uid)
             virtual UserGroup_t* GetUserInfo(const char* user = "0")
              virtual const char* HomeDirectory(const char* userName = "0") const
              virtual const char* HostName() const
                     virtual void IgnoreInterrupt(Bool_t ignore = kTRUE)
                     virtual void IgnoreSignal(ESignals sig, Bool_t ignore = kTRUE)
                           Bool_t InControl() const
                   virtual Bool_t Init()
                     virtual void InnerLoop()
                  virtual TClass* IsA() const
                   virtual Bool_t IsAbsoluteFileName(const char* dir)
                   virtual Bool_t IsFileInIncludePath(const char* name, char** fullpath = "0")
                      virtual int Link(const char* from, const char* to)
                     virtual void ListLibraries(const char* regexp = "")
                     virtual void ListSymbols(const char* module, const char* re = "")
                      virtual int Load(const char* module, const char* entry = "", Bool_t system = kFALSE)
                      virtual int MakeDirectory(const char* name)
                      virtual int mkdir(const char* name, Bool_t recursive = kFALSE)
                   virtual Long_t NextTimeOut(Bool_t mode)
                    virtual TTime Now()
                      virtual int OpenConnection(const char* server, int port, int tcpwindowsize = -1)
                    virtual void* OpenDirectory(const char* name)
                     virtual void Openlog(const char* name, Int_t options, ELogFacility facility)
                    virtual FILE* OpenPipe(const char* command, const char* mode)
                         TSystem& operator=(const TSystem&)
                   virtual Bool_t ProcessEvents()
                      const char* pwd() const
                      virtual int RecvBuf(int sock, void* buffer, int length)
                      virtual int RecvRaw(int sock, void* buffer, int length, int flag)
            virtual TFileHandler* RemoveFileHandler(TFileHandler* fh)
                             void RemoveOnExit(TObject* obj)
          virtual TSignalHandler* RemoveSignalHandler(TSignalHandler* sh)
                  virtual TTimer* RemoveTimer(TTimer* t)
                      virtual int Rename(const char* from, const char* to)
                      static void ResetErrno()
                     virtual void ResetSignal(ESignals sig, Bool_t reset = kTRUE)
                     virtual void ResetTimer(TTimer*)
                     virtual void Run()
                    virtual Int_t Select(TList* active, Long_t timeout)
                    virtual Int_t Select(TFileHandler* fh, Long_t timeout)
                      virtual int SendBuf(int sock, const void* buffer, int length)
                      virtual int SendRaw(int sock, const void* buffer, int length, int flag)
                     virtual void SetAclicMode(TSystem::EAclicMode mode)
                     virtual void SetBuildDir(const char*)
                     virtual void SetDisplay()
                     virtual void SetDynamicPath(const char* pathname)
                     virtual void Setenv(const char* name, const char* value)
                             void SetErrorStr(const char* errstr)
                     virtual void SetFlagsDebug(const char*)
                     virtual void SetFlagsOpt(const char*)
                    virtual Int_t SetFPEMask(Int_t mask = kDefaultMask)
                     virtual void SetIncludePath(const char* includePath)
                     virtual void SetLinkdefSuffix(const char* suffix)
                     virtual void SetLinkedLibs(const char* linkedLibs)
                     virtual void SetMakeExe(const char* directives)
                     virtual void SetMakeSharedLib(const char* directives)
                     virtual void SetObjExt(const char* objExt)
                     virtual void SetProgname(const char* name)
                      virtual int SetSockOpt(int sock, int kind, int val)
                     virtual void SetSoExt(const char* soExt)
                     virtual void ShowMembers(TMemberInspector& insp, char* parent)
                     virtual void Sleep(UInt_t milliSec)
                  virtual TString SplitAclicMode(const char* filename, TString& mode, TString& args, TString& io) const
                     virtual void StackTrace()
                     virtual void Streamer(TBuffer& b)
                             void StreamerNVirtual(TBuffer& b)
                      virtual int Symlink(const char* from, const char* to)
                     virtual void Syslog(ELogLevel level, const char* mess)
              virtual const char* TempDirectory() const
                    virtual FILE* TempFileName(TString& base, const char* dir = "0")
                      virtual int Umask(Int_t mask)
              virtual const char* UnixPathName(const char* unixpathname) const
                      virtual int Unlink(const char* name)
                     virtual void Unload(const char* module)
                     virtual void Unsetenv(const char* name)
                      virtual int Utime(const char* file, Long_t modtime, Long_t actime)
                    virtual char* Which(const char* search, const char* file, EAccessMode mode = kFileExists)
              virtual const char* WorkingDirectory() const

Data Members

    protected:

                  TFdSet* fReadmask         !Files that should be checked for read events
                  TFdSet* fWritemask        !Files that should be checked for write events
                  TFdSet* fReadready        !Files with reads waiting
                  TFdSet* fWriteready       !Files with writes waiting
                  TFdSet* fSignals          !Signals that were trapped
                    Int_t fNfd              Number of fd's in masks
                    Int_t fMaxrfd           Largest fd in read mask
                    Int_t fMaxwfd           Largest fd in write mask
                    Int_t fSigcnt           Number of pending signals
                  TString fWdpath           Working directory
                  TString fHostname         Hostname
                   Bool_t fInsideNotify     Used by DispatchTimers()
                   Bool_t fInControl        True if in eventloop
                   Bool_t fDone             True if eventloop should be finished
                    Int_t fLevel            Level of nested eventloops
                  TString fLastErrorString  Last system error message
          TSeqCollection* fTimers           List of timers
          TSeqCollection* fSignalHandler    List of signal handlers
          TSeqCollection* fFileHandler      List of file handlers
          TSeqCollection* fOnExitList       List of items to be cleaned-up on exit
                  TString fListLibs         List shared libraries, cache used by GetLibraries
                  TString fBuildArch        Architecure for which ROOT was built (passed to ./configure)
                  TString fBuildNode        Detailed information where ROOT was built
                  TString fBuildDir         Location where to build ACLiC shared library and use as scratch area.
                  TString fFlagsDebug       Flags for debug compilation
                  TString fFlagsOpt         Flags for optimized compilation
                  TString fListPaths        List of all include (fIncludePath + interpreter include path). Cache used by GetIncludePath
                  TString fIncludePath      Used to expand $IncludePath in the directives given to SetMakeSharedLib and SetMakeExe
                  TString fLinkedLibs       Used to expand $LinkedLibs in the directives given to SetMakeSharedLib and SetMakeExe
                  TString fSoExt            Extension of shared library (.so, .sl, .a, .dll, etc.)
                  TString fObjExt           Extension of object files (.o, .obj, etc.)
      TSystem::EAclicMode fAclicMode        Whether the compilation should be done debug or opt
                  TString fMakeSharedLib    Directive used to build a shared library
                  TString fMakeExe          Directive used to build an executable
                  TString fLinkdefSuffix    Default suffix for linkdef files to be used by ACLiC
          TSeqCollection* fCompiled         List of shared libs from compiled macros to be deleted
          TSeqCollection* fHelpers          List of helper classes for alternative file/directory access

    public:

      static const TSystem::EAclicMode kDefault  
      static const TSystem::EAclicMode kDebug    
      static const TSystem::EAclicMode kOpt      

Class Description

                                                                      
 TSystem                                                              
                                                                      
 Abstract base class defining a generic interface to the underlying   
 Operating System.                                                    
 This is not an ABC in the strict sense of the (C++) word. For        
 every member function their is an implementation (often not more     
 than a call to AbstractMethod() which prints a warning saying        
 that the method should be overridden in a derived class), which      
 allows a simple partial implementation for new OS'es.                
                                                                      

 Create a new OS interface.

 Delete the OS interface.

 Initialize the OS interface.

 Set the application name (from command line, argv[0]) and copy it in
 gProgName.

 Set DISPLAY environment variable based on utmp entry. Only for UNIX.

 Set the system error string. This string will be used by GetError().
 To be used in case one does not want or can use the system error
 string (e.g. because error is generated by a third party POSIX like
 library that does not use standard errno).

 Return system error string.

 Static function returning system error number.

 Static function resetting system error number.

 Objects that should be deleted on exit of the OS interface.

 Return the system's host name.

 System event loop.

 Exit from event loop.

 Inner event loop.

 Process pending events (GUI, timers, sockets). Returns the result of
 TROOT::IsInterrupted(). The interrupt flag (TROOT::SetInterrupt())
 can be set during the handling of the events. This mechanism allows
 macros running in tight calculating loops to be interrupted by some
 GUI event (depending on the interval with which this method is
 called). For example hitting ctrl-c in a canvas will set the
 interrupt flag.

 Dispatch a single event.

 Sleep milliSec milli seconds.

 Select on active file descriptors (called by TMonitor).

 Select on active file descriptors (called by TMonitor).

 Return current time.

 Add timer to list of system timers.

 Remove timer from list of system timers. Returns removed timer or 0
 if timer was not active.

 Time when next timer of mode (synchronous=kTRUE or
 asynchronous=kFALSE) will time-out (in ms).

 Add a signal handler to list of system signal handlers. Only adds
 the handler if it is not already in the list of signal handlers.

 Remove a signal handler from list of signal handlers. Returns
 the handler or 0 if the handler was not in the list of signal handlers.

 Add a file handler to the list of system file handlers. Only adds
 the handler if it is not already in the list of file handlers.

 Remove a file handler from the list of file handlers. Returns
 the handler or 0 if the handler was not in the list of file handlers.

 If reset is true reset the signal handler for the specified signal
 to the default handler, else restore previous behaviour.

 If ignore is true ignore the specified signal, else restore previous
 behaviour.

 If ignore is true ignore the interrupt signal, else restore previous
 behaviour. Typically call ignore interrupt before writing to disk.

 Return the bitmap of conditions that trigger a floating point exception.

 Set which conditions trigger a floating point exception.
 Return the previous set of conditions.

 Execute a command.

 Open a pipe.

 Close the pipe.

 Get process id.

 Exit the application.

 Abort the application.

 Print a stack trace.

 Create helper TSystem to handle file and directory operations that
 might be special for remote file access, like via rfiod or rootd.

 Check consistency of this helper with the one required
 by 'path' or 'dirptr'

 Make a directory. Returns 0 in case of success and
 -1 if the directory could not be created (either already exists or
 illegal path name).

 Open a directory. Returns 0 if directory does not exist.

 Free a directory.

 Get a directory entry. Returns 0 if no more entries.

 Change directory.

 Return working directory.

 Return the user's home directory.

 Make a file system directory. Returns 0 in case of success and
 -1 if the directory could not be created (either already exists or
 illegal path name).
 If 'recursive' is true, makes parent directories as needed.

 Base name of a file name. Base name of /user/root is root.

 Return true if dir is an absolute pathname.

 Return true if 'name' is a file that can be found in the ROOT include
 path or the current directory.
 If 'name' contains any ACLiC style information (e.g. trailing +[+][g|O]),
 it will be striped off 'name'.
 If fullpath is != 0, the full path to the file is returned in *fullpath,
 which must be deleted by the caller.

 Return the directory name in pathname. DirName of /user/root is /user.

 Convert from a Unix pathname to a local pathname. E.g. from /user/root to \user\root.

 Concatenate a directory and a file name.

 Expand a pathname getting rid of special shell characters like ~.$, etc.
 For Unix/Win32 compatibility use $(XXX) instead of $XXX when using
 environment variables in a pathname. If compatibility is not an issue
 you can use on Unix directly $XXX. This is a protected function called
 from the OS specific system classes, like TUnixSystem and TWinNTSystem.

 Expand a pathname getting rid of special shell characaters like ~.$, etc.
 For Unix/Win32 compatibility use $(XXX) instead of $XXX when using
 environment variables in a pathname. If compatibility is not an issue
 you can use on Unix directly $XXX.

 Expand a pathname getting rid of special shell characaters like ~.$, etc.
 For Unix/Win32 compatibility use $(XXX) instead of $XXX when using
 environment variables in a pathname. If compatibility is not an issue
 you can use on Unix directly $XXX. The user must delete returned string.

 Returns FALSE if one can access a file using the specified access mode.
 The file name must not contain any special shell characters line ~ or $,
 in those cases first call ExpandPathName().
 Attention, bizarre convention of return value!!

 Copy a file. If overwrite is true and file already exists the
 file will be overwritten. Returns 0 when successful, -1 in case
 of failure, -2 in case the file already exists and overwrite was false.

 Rename a file.

 Create a link from file1 to file2.

 Create a symbolic link from file1 to file2.

 Unlink, i.e. remove, a file.

 Get info about a file: id, size, flags, modification time.
 Id      is (statbuf.st_dev << 24) + statbuf.st_ino
 Size    is the file size
 Flags   is file type: 0 is regular file, bit 0 set executable,
                       bit 1 set directory, bit 2 set special file
                       (socket, fifo, pipe, etc.)
 Modtime is modification time.
 The function returns 0 in case of success and 1 if the file could
 not be stat'ed.

 Get info about a file: id, size, flags, modification time.
 Id      is (statbuf.st_dev << 24) + statbuf.st_ino
 Size    is the file size
 Flags   is file type: 0 is regular file, bit 0 set executable,
                       bit 1 set directory, bit 2 set special file
                       (socket, fifo, pipe, etc.)
 Modtime is modification time.
 The function returns 0 in case of success and 1 if the file could
 not be stat'ed.

 Get info about a file. Info is returned in the form of a FileStat_t
 structure (see TSystem.h).
 The function returns 0 in case of success and 1 if the file could
 not be stat'ed.

 Get info about a file system: fs type, block size, number of blocks,
 number of free blocks.

 Return a user configured or systemwide directory to create
 temporary files in.

 Create a secure temporary file by appending a unique
 6 letter string to base. The file will be created in
 a standard (system) directory or in the directory
 provided in dir. The full filename is returned in base
 and a filepointer is returned for safely writing to the file
 (this avoids certain security problems). Returns 0 in case
 of error.

 Set the file permission bits. Returns -1 in case or error, 0 otherwise.

 Set the process file creation mode mask.

 Set the a files modification and access times. If actime = 0 it will be
 set to the modtime. Returns 0 on success and -1 in case of error.

 Find location of file in a search path. User must delete returned string.
 Returns 0 in case file is not found.

 Returns the user's id. If user = 0, returns current user's id.

 Returns the effective user id. The effective id corresponds to the
 set id bit on the file being executed.

 Returns the group's id. If group = 0, returns current user's group.

 Returns the effective group id. The effective group id corresponds
 to the set id bit on the file being executed.

 Returns all user info in the UserGroup_t structure. The returned
 structure must be deleted by the user. In case of error 0 is returned.

 Returns all user info in the UserGroup_t structure. If user = 0, returns
 current user's id info. The returned structure must be deleted by the
 user. In case of error 0 is returned.

 Returns all group info in the UserGroup_t structure. The only active
 fields in the UserGroup_t structure for this call are:
    fGid and fGroup
 The returned structure must be deleted by the user. In case of
 error 0 is returned.

 Returns all group info in the UserGroup_t structure. The only active
 fields in the UserGroup_t structure for this call are:
    fGid and fGroup
 If group = 0, returns current user's group. The returned structure
 must be deleted by the user. In case of error 0 is returned.

 Set environment variable.

 Unset environment variable.

 Get environment variable.

 Open connection to system log daemon. For the use of the options and
 facility see the Unix openlog man page.

 Send mess to syslog daemon. Level is the logging level and mess the
 message that will be written on the log.

 Close connection to system log daemon.

 Return the dynamic path (used to find shared libraries).

 Set the dynamic path to a new value.
 If the value of 'path' is zero, the dynamic path is reset to its
 default value.

 Load a shared library. Returns 0 on successful loading, 1 in
 case lib was already loaded and -1 in case lib does not exist
 or in case of error. When entry is specified the loaded lib is
 search for this entry point (return -1 when entry does not exist,
 0 otherwise). When the system flag is kTRUE, the library is consisdered
 a permanent systen library that should not be unloaded during the
 course of the session.

 Find specific entry point in specified library. Specify "*" for lib
 to search in all libraries.

 Unload a shared library.

 List symbols in a shared library.

 List all loaded shared libraries.

 Get list of shared libraries loaded at the start of the executable.
 Returns 0 in case list cannot be obtained or in case of error.

 Return a space separated list of loaded shared libraries.
 This list is of a format suitable for a linker, i.e it may contain
 -Lpathname and/or -lNameOfLib.
 Option can be any of:
   S: shared libraries loaded at the start of the executable, because
      they were specified on the link line.
   D: shared libraries dynamically loaded after the start of the program.
 For MacOS only:
   L: list the .dylib rather than the .so (this is intended for linking)
      [This options is not the default]

 Get Internet Protocol (IP) address of host.

 Get Internet Protocol (IP) address of remote host and port #.

 Get Internet Protocol (IP) address of host and port #.

 Get port # of internet service.

 Get name of internet service.

 Open a connection to another host.

 Announce TCP/IP service.

 Announce unix domain service.

 Accept a connection.

 Close socket connection.

 Receive exactly length bytes into buffer. Use opt to receive out-of-band
 data or to have a peek at what is in the buffer (see TSocket).

 Send exactly length bytes from buffer. Use opt to send out-of-band
 data (see TSocket).

 Receive a buffer headed by a length indicator.

 Send a buffer headed by a length indicator.

 Set socket option.

 Get socket option.

 This method compiles and loads a shared library containing
 the code from the file "filename".

 The possible options are:
     k : keep the shared library after the session end.
     f : force recompilation.
     g : compile with debug symbol
     O : optimized the code (ignore if 'g' is specified)
     c : compile only, do not attempt to the load the library.

 If library_specified is specified, CompileMacro generates the file
 "library_specified".soext where soext is the shared library extension for
 the current platform.

 If build_dir is specified, it is used as an alternative 'root' for the
 generation of the shared library.  The library is stored in a sub-directories
 of 'build_dir' including the full pathname of the script.  See also
 TSystem::SetBuildDir.

 If library_specified is not specified, CompileMacro generate a default name
 for library by taking the name of the file "filename" but replacing the
 dot before the extension by an underscore and by adding the shared
 library extension for the current platform.
 For example on most platform, hsimple.cxx will generate hsimple_cxx.so

 It uses the directive fMakeSharedLibs to create a shared library.
 If loading the shared library fails, it tries to output a list of missing
 symbols by creating an executable (on some platforms like OSF, this does
 not HAVE to be an executable) containing the script. It uses the
 directive fMakeExe to do so.
 For both directives, before passing them to TSystem::Exec, it expands the
 variables $SourceFiles, $SharedLib, $LibName, $IncludePath, $LinkedLibs,
 $ExeName and $ObjectFiles. See SetMakeSharedLib() for more information on
 those variables.

 This method is used to implement the following feature:

 Synopsis:

 The purpose of this addition is to allow the user to use an external
 compiler to create a shared library from its C++ macro (scripts).
 Currently in order to execute a script, a user has to type at the root
 prompt

  .X myfunc.C(arg1,arg2)

 We allow him to type:

  .X myfunc.C++(arg1,arg2)
 or
  .X myfunc.C+(arg1,arg2)

 In which case an external compiler will be called to create a shared
 library.  This shared library will then be loaded and the function
 myfunc will be called with the two arguments.  With '++' the shared library
 is always recompiled.  With '+' the shared library is recompiled only
 if it does not exist yet or the macro file is newer than the shared
 library.

 Of course the + and ++ notation is supported in similar way for .x and .L.

 Through the function TSystem::SetMakeSharedLib(), the user will be able to
 indicate, with shell commands, how to build a shared library (a good
 default will be provided). The most common change, namely where to find
 header files, will be available through the function
 TSystem::SetIncludePath().
 A good default will be provided so that a typical user session should be at
 most:

 root[1] gSystem->SetIncludePath("-I$ROOTSYS/include
 -I$HOME/mypackage/include");
 root[2] .x myfunc.C++(10,20);

 The user may sometimes try to compile a script before it has loaded all the
 needed shared libraries.  In this case we want to be helpfull and output a
 list of the unresolved symbols. So if the loading of the created shared
 library fails, we will try to build a executable that contains the
 script. The linker should then output a list of missing symbols.

 To support this we provide a TSystem::SetMakeExe() function, that sets the
 directive telling how to create an executable. The loader will need
 to be informed of all the libraries available. The information about
 the libraries that has been loaded by .L and TSystem::Load() is accesible
 to the script compiler. However, the information about
 the libraries that have been selected at link time by the application
 builder (like the root libraries for root.exe) are not available and need
 to be explictly listed in fLinkedLibs (either by default or by a call to
 TSystem::SetLinkedLibs()).

 To simplify customization we could also add to the .rootrc support for the
 variables

 Unix.*.Root.IncludePath:     -I$ROOTSYS/include
 WinNT.*.Root.IncludePath:    -I%ROOTSYS%/include

 Unix.*.Root.LinkedLibs:      -L$ROOTSYS/lib -lBase ....
 WinNT.*.Root.LinkedLibs:     %ROOTSYS%/lib/*.lib msvcrt.lib ....

 And also support for MakeSharedLibs() and MakeExe().

 (the ... have to be replaced by the actual values and are here only to
 shorten this comment).

 Set the location where ACLiC will create libraries and use as
 a scratch area.  Note that the libraries are actually stored in
 sub-directories of 'build_dir' including the full pathname of the
 script.  If the script is location at /full/path/name/macro.C
 the library will be located at 'build_dir+/full/path/name/macro_C.so'

 FlagsDebug should contain the options to pass to the C++ compiler
 in order to compile the library in debug mode.

 FlagsOpt should contain the options to pass to the C++ compiler
 in order to compile the library in optimized mode.

 AclicMode indicates whether the library should be built in
 debug mode or optimized.  The values are:
 TSystem::kDefault : compile the same as the current ROOT
 TSystem::kDebug : compiled in debug mode
 TSystem::kOpt : optimized the library

 Directives has the same syntax as the argument of SetMakeSharedLib but is
 used to create an executable. This creation is used as a means to output
 a list of unresolved symbols, when loading a shared library has failed.
 The required variable is $ExeName rather than $SharedLib, e.g.:
 gSystem->SetMakeExe(
 "g++ -Wall -fPIC $IncludePath $SourceFiles
  -o $ExeName $LinkedLibs -L/usr/X11R6/lib -lX11 -lm -ldl -rdynamic");

 Directives should contain the description on how to compile and link a
 shared lib. This description can be any valid shell command, including
 the use of ';' to separate several instructions. However, shell specific
 construct should be avoided. In particular this description can contain
 environment variables, like $ROOTSYS (or %ROOTSYS% on windows).

 Five special variables will be expanded before execution:
   Variable name       Expands to
   -------------       ----------
   $SourceFiles        Name of source files to be compiled
   $SharedLib          Name of the shared library being created
   $LibName            Name of shared library without extension
   $BuildDir           Directory where the files will be created
   $IncludePath        value of fIncludePath
   $LinkedLibs         value of fLinkedLibs
   $ObjectFiles        Name of source files to be compiler with
                       their extension changed to .o or .obj
   $Opt                location of the optimization/debug options
                       set fFlagsDebug and fFlagsOpt

 e.g.:
 gSystem->SetMakeSharedLib(
 "KCC -n32 --strict $IncludePath -K0 \$Opt $SourceFile
  --no_exceptions --signed_chars --display_error_number
  --diag_suppress 68 -o $SharedLib");

 gSystem->setMakeSharedLib(
 "Cxx $IncludePath -c $SourceFile;
  ld  -L/usr/lib/cmplrs/cxx -rpath /usr/lib/cmplrs/cxx -expect_unresolved
  \$Opt -shared /usr/lib/cmplrs/cc/crt0.o /usr/lib/cmplrs/cxx/_main.o
  -o $SharedLib $ObjectFile -lcxxstd -lcxx -lexc -lots -lc"

 gSystem->SetMakeSharedLib(
 "$HOME/mygcc/bin/g++ \$Opt -Wall -fPIC $IncludePath $SourceFile
  -shared -o $SharedLib");

 gSystem->SetMakeSharedLib(
 "cl -DWIN32  -D_WIN32 -D_MT -D_DLL -MD /O2 /G5 /MD -DWIN32
  -DVISUAL_CPLUSPLUS -D_WINDOWS $IncludePath $SourceFile
  /link -PDB:NONE /NODEFAULTLIB /INCREMENTAL:NO /RELEASE /NOLOGO
  $LinkedLibs -entry:_DllMainCRTStartup@12 -dll /out:$SharedLib")

 Add includePath to the already set include path.

 Add linkedLib to already set linked libs.

 IncludePath should contain the list of compiler flags to indicate where
 to find user defined header files. It is used to expand $IncludePath in
 the directives given to SetMakeSharedLib() and SetMakeExe(), e.g.:
    gSystem->SetInclude("-I$ROOTSYS/include -Imydirectory/include");
 the default value of IncludePath on Unix is:
    "-I$ROOTSYS/include "
 and on Windows:
    "/I%ROOTSYS%/include "

 LinkedLibs should contain the library directory and list of libraries
 needed to recreate the current executable. It is used to expand $LinkedLibs
 in the directives given to SetMakeSharedLib() and SetMakeExe()
 The default value on Unix is: root-config --glibs

 The 'suffix' will be appended to the name of a script loaded by ACLiC
 and used to locate any eventual additional linkdef information that
 ACLiC should used to produce the dictionary.
 So by default, when doing .L MyScript.cxx, ACLiC will look
 for a file name MyScript_linkdef and having one of the .h (.hpp,
 etc.) extensions.  If such a file exist, it will be added to
 the end of the linkdef file used to created the ACLiC dictionary.
 This effectively enable the full customization of the creation
 of the dictionary.  It should be noted that the file is intended
 as a linkdef 'fragment', so usually you would not list the
 typical '#pragma link off ....".

 Set shared library extension, should be either .so, .sl, .a, .dll, etc.

 Set object files extension, should be either .o, .obj, etc.

 This method split a filename of the form:
   [path/]macro.C[+|++[g|O]][(args)].
 It stores the ACliC mode [+|++[g|O]] in 'mode',
 the arguments (including paranthesis) in arg
 and the I/O indirection in io

 Remove the shared libs produced by the CompileMacro() function.

Inline Functions

                       void SigAlarmInterruptsSyscalls(Bool_t)
                const char* GetErrorStr() const
                     Bool_t InControl() const
            TSeqCollection* GetListOfFileHandlers() const
                       void ResetTimer(TTimer*)
                      void* GetDirPtr() const
                     Bool_t cd(const char* path)
                const char* pwd() const
        TSystem::EAclicMode GetAclicMode() const
                    TClass* Class()
                    TClass* IsA() const
                       void ShowMembers(TMemberInspector& insp, char* parent)
                       void Streamer(TBuffer& b)
                       void StreamerNVirtual(TBuffer& b)
                    TSystem TSystem(const TSystem&)
                   TSystem& operator=(const TSystem&)