Source: kprocess.h

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    /* This file is part of the KDE libraries
        Copyright (C) 1997 Christian Czezakte (e9025461@student.tuwien.ac.at)

        This library is free software; you can redistribute it and/or
        modify it under the terms of the GNU Library General Public
        License as published by the Free Software Foundation; either
        version 2 of the License, or (at your option) any later version.

        This library is distributed in the hope that it will be useful,
        but WITHOUT ANY WARRANTY; without even the implied warranty of
        MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
        Library General Public License for more details.

        You should have received a copy of the GNU Library General Public License
        along with this library; see the file COPYING.LIB.  If not, write to
        the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
        Boston, MA 02111-1307, USA.
    */
    //
    //  KPROCESS -- A class for handling child processes in KDE without
    //  having to take care of Un*x specific implementation details
    //
    //  version 0.3.1, Jan 8th 1998
    //
    //  (C) Christian Czezatke
    //  e9025461@student.tuwien.ac.at
    //

    #ifndef __kprocess_h__
    #define __kprocess_h__

    #include <sys/types.h> // for pid_t
    #include <sys/wait.h>
    #include <signal.h>
    #include <unistd.h>
    #include <qstrlist.h>
    #include <qobject.h>
    #include <qsocketnotifier.h>

    class KProcessPrivate;

    /**
     *  Child process invocation, monitoring and control.
     *
     * @sect General usage and features
     *
     *This class allows a KDE application to start child processes without having
     *to worry about UN*X signal handling issues and zombie process reaping.
     *
     *Basically, this class distinguishes three different ways of running
     *child processes:
     *
     *@li  KProcess::DontCare -- The child process is invoked and both the child
     *process and the parent process continue concurrently.
     *
     *Starting a  DontCare child process means that the application is
     *not interested in any notification to determine whether the
     *child process has already exited or not.
     *
     *@li  KProcess::NotifyOnExit -- The child process is invoked both the
     *child and the parent process run concurrently.
     *
     *When the child process exits, the KProcess instance
     *corresponding to it emits the Qt signal @ref processExited().
     *
     *Since this signal is @em not emitted from within a UN*X
     *signal handler, arbitrary function calls can be made.
     *
     *@li  KProcess::Block -- The child process starts and the parent process
     *is suspended until the child process exits. (@em Really not recommended
     *for programs with a GUI.)
     *
     *KProcess also provides several functions for determining the exit status
     *and the pid of the child process it represents.
     *
     *Furthermore it is possible to supply command-line arguments to the process
     *in a clean fashion (no null -- terminated stringlists and such...)
     *
     *A small usage example:
     *<pre>
     *KProcess proc;
     *
     *proc << "my_executable";
     *proc << "These" << "are" << "the" << "command" << "line" << "args";
     *QApplication::connect(&proc, SIGNAL(processExited(KProcess *)),
     *                      pointer_to_my_object, SLOT(my_objects_slot));
     *proc.start();
     *</pre>
     *
     *This will start "my_executable" with the commandline arguments "These"...
     *
     *When the child process exits, the respective Qt signal will be emitted.
     *
     *@sect Communication with the child process
     *
     *KProcess supports communication with the child process through
     *stdin/stdout/stderr.
     *
     *The following functions are provided for getting data from the child
     *process or sending data to the child's stdin (For more information,
     *have a look at the documentation of each function):
     *
     *@li bool @ref writeStdin(char  *buffer, int  buflen);
     *@li  -- Transmit data to the child process's stdin.
     *
     *@li bool @ref closeStdin();
     *@li -- Closes the child process's stdin (which causes it to see an  feof(stdin)).
     *Returns false if you try to close stdin for a process that has been started
     *without a communication channel to stdin.
     *
     *@li bool @ref closeStdout();
     *@li -- Closes the child process's stdout.
     *Returns false if you try to close stdout for a process that has been started
     *without a communication channel to stdout.
     *
     *@li bool @ref closeStdout();
     *@li -- Closes the child process's stderr.
     *Returns false if you try to close stderr for a process that has been started
     *without a communication channel to stderr.
     *
     *
     *@sect QT signals:
     *
     *@li void @ref receivedStdout(KProcess  *proc, char  *buffer, int  buflen);
     *@li  void @ref receivedStderr(KProcess  *proc, char  *buffer, int  buflen);
     *@li  -- Indicates that new data has arrived from either the
     *child process's stdout or stderr.
     *
     *@li  void @ref wroteStdin(KProcess  *proc);
     *@li  -- Indicates that all data that has been sent to the child process
     *by a prior call to @ref writeStdin() has actually been transmitted to the
     *client .
     *
     *@author Christian Czezakte e9025461@student.tuwien.ac.at
     *
     *
     **/
    class KProcess : public QObject
    {
      Q_OBJECT

    public:

      /**
       * Modes in which the communication channel can be opened.
       *
       * If communication for more than one channel is required,
       * the values have to be or'ed together, for example to get
       * communication with stdout as well as with stdin, you would
       * specify @p Stdin @p | @p Stdout
       *
       * If @p NoRead is specified in conjunction with @p Stdout,
       * no data is actually read from @p Stdout but only
       * the signal @ref childOutput(int fd) is emitted.
       */
      enum Communication { NoCommunication = 0, Stdin = 1, Stdout = 2, Stderr = 4,
    					   AllOutput = 6, All = 7,
    					   NoRead };

      /**
       * Run-modes for a child process.
       *
       * @see  KProcess
      */
      enum RunMode { DontCare, NotifyOnExit, Block };

      /** Constructor */
      KProcess();

      /**
       *Destructor:
       *
       *  If the process is running when the destructor for this class
       *  is called, the child process is killed with a SIGKILL, but
       *  only if the run mode is not of type @p DontCare.
       *  Processes started as @p DontCare keep running anyway.
      */
      virtual ~KProcess();

      /**
       @deprecated

             The use of this function is now deprecated. -- Please use the
    	 "operator<<" instead of "setExecutable".

    	 Sets the executable to be started with this KProcess object.
    	 Returns false if the process is currently running (in that
    	 case the executable remains unchanged.)

    	 @see operator<<

      */
      bool setExecutable(const QString& proc);

      /**
       * Sets the executable and the command line argument list for this process.
       *
       * For example, doing an "ls -l /usr/local/bin" can be achieved by:
       *  <pre>
       *  KProcess p;
       *  ...
       *  p << "ls" << "-l" << "/usr/local/bin"
       *  </pre>
       *
       **/
      KProcess &operator<<(const QString& arg);

      /**
       * Clear a command line argument list that has been set by using
       * the "operator<<".
      */
      void clearArguments();

      /** Start the process.
       *  For a detailed description of the
       *  various run modes and communication semantics, have a look at the
       *  general description of the @ref KProcess class.
       *
       *  The following problems could cause @ref KProcess:start() to
       *    return @p false:
       *
       *  @li The process is already running.
       *  @li The command line argument list is empty.
       *  @li The starting of the process failed (could not fork).
       *  @li The executable was not found.
       *
       *  @param comm  Specifies which communication links should be
       *  established to the child process (stdin/stdout/stderr). By default,
       *  no communication takes place and the respective communication
       *  signals will never get emitted.
       *
       *  @return @p true on success, @p false on error
       *  (see above for error conditions)
       **/
      virtual bool start(RunMode  runmode = NotifyOnExit,
      	Communication comm = NoCommunication);

      /**
       * Stop the process (by sending it a signal).
       *
       * @param signo	The signal to send. The default is SIGTERM.
       * @return @p true if the signal was delivered successfully.
      */
      virtual bool kill(int signo = SIGTERM);

      /**
         @return @p true if the process is (still) considered to be running
      */
      bool isRunning() const;

      /** Returns the process id of the process.
       *
       * If it is called after
       * the process has exited, it returns the process id of the last
       *  child process that was created by this instance of KProcess.
       *
       *  Calling it before any child process has been started by this
       *  KProcess instance causes pid() to return 0.
       **/
      pid_t pid() const;

      /**
       * Use pid().
       * @deprecated
       */
      pid_t getPid() const { return pid(); }

      /**
       * Suspend processing of data from stdout of the child process.
       */
      void suspend();

      /**
       * Resume processing of data from stdout of the child process.
       */
      void resume();

      /**
       * @return @p true if the process has already finished and has exited
       *  "voluntarily", ie: it has not been killed by a signal.
       *
       * Note that you should check @ref KProcess::exitStatus() to determine
       * whether the process completed its task successfull or not.
       */
      bool normalExit() const;

      /**
       * Retrieve the exit status of the process.
       *
       * Please use
       * @ref KProcess::normalExit() to check whether the process has exited
       * cleanly (i.e., @ref KProcess::normalExit() returns @p true) before calling
       * this function because if the process did not exit normally,
       * it does not have a valid exit status.
      */
      int  exitStatus() const;

      /**
       *	 Transmit data to the child process's stdin.
       *
       * KProcess::writeStdin may return false in the following cases:
       *
       *     @li The process is not currently running.
       *
       *     @li Communication to stdin has not been requested in the @ref start() call.
       *
       *     @li Transmission of data to the child process by a previous call to
       * @ref writeStdin() is still in progress.
       *
       * Please note that the data is sent to the client asynchronousely,
       * so when this function returns, the data might not have been
       * processed by the child process.
       *
       * If all the data has been sent to the client, the signal
       * @ref wroteStdin() will be emitted.
       *
       * Please note that you must not free "buffer" or call @ref writeStdin()
       * again until either a @ref wroteStdin() signal indicates that the
       * data has been sent or a @ref processHasExited() signal shows that
       * the child process is no longer alive...
       **/
      bool writeStdin(const char *buffer, int buflen);

      /**
       * This causes the stdin file descriptor of the child process to be
       * closed indicating an "EOF" to the child.
       *
       * @return @p false if no communication to the process's stdin
       *  had been specified in the call to @ref start().
      */
      bool closeStdin();

      /**
       * This causes the stdout file descriptor of the child process to be
       * closed.
       *
       * @return @p false if no communication to the process's stdout
       *  had been specified in the call to @ref start().
      */
      bool closeStdout();

      /**
       * This causes the stderr file descriptor of the child process to be
       * closed.
       *
       * @return @p false if no communication to the process's stderr
       *  had been specified in the call to @ref start().
      */
      bool closeStderr();

      /**
       * Lets you see what your arguments are for debugging.
       */

      QStrList * args() { return &arguments; }

      /**
       * Controls whether the started process should drop any
       * setuid/segid privileges or whether it should keep them
       *
       * The default is @p false : drop privileges
       */
      void setRunPrivileged(bool keepPrivileges);

      /**
       * Returns whether the started process will drop any
       * setuid/segid privileges or whether it will keep them
       */
      bool runPrivileged() const;

    signals:

      /**
       * Emitted after the process has terminated when
       * the process was run in the @p NotifyOnExit  (==default option to
       * @ref start()) or the @ref Block mode.
       **/
      void processExited(KProcess *proc);

      /**
       * Emitted, when output from the child process has
       * been received on stdout.
       *
       *  To actually get
       * these signals, the respective communication link (stdout/stderr)
       * has to be turned on in @ref start().
       *
       * @param buffer The data received.
       * @param buflen The number of bytes that are available.
       *
       * You should copy the information contained in @p buffer to your private
       * data structures before returning from this slot.
       **/
      void receivedStdout(KProcess *proc, char *buffer, int buflen);

      /**
       * Emitted when output from the child process has
       * been received on stdout.
       *
       *  To actually get
       * these signals, the respective communications link (stdout/stderr)
       * has to be turned on in @ref start() and the @p NoRead flag should
       * have been passed.
       *
       * The data still has to be read from file descriptor @p fd.
       **/
      void receivedStdout(int fd, int &len);

      /**
       * Emitted, when output from the child process has
       * been received on stderr.
       * To actually get
       * these signals, the respective communication link (stdout/stderr)
       * has to be turned on in @ref start().
       *
       * @param buffer The data received.
       * @param buflen The number of bytes that are available.
       *
       * You should copy the information contained in @p buffer to your private
       * data structures before returning from this slot.
      */
      void receivedStderr(KProcess *proc, char *buffer, int buflen);

      /**
       * Emitted after all the data that has been
       * specified by a prior call to @ref writeStdin() has actually been
       * written to the child process.
       **/
      void wroteStdin(KProcess *proc);

    protected slots:

     /**
       This slot gets activated when data from the child's stdout arrives.
       It usually calls "childOutput"
      */
      void slotChildOutput(int fdno);

     /**
       This slot gets activated when data from the child's stderr arrives.
       It usually calls "childError"
      */
      void slotChildError(int fdno);
      /*
    	Slot functions for capturing stdout and stderr of the child
      */

      /**
    	Called when another bulk of data can be sent to the child's
    	stdin. If there is no more data to be sent to stdin currently
    	available, this function must disable the QSocketNotifier "innot".
      */
      void slotSendData(int dummy);

    protected:

      /**
         The list of the process' command line arguments. The first entry
         in this list is the executable itself.
      */
      QStrList arguments;
      /**
         How to run the process (Block, NotifyOnExit, DontCare). You should
         not modify this data member directly from derived classes.
      */
      RunMode run_mode;
      /**
         true if the process is currently running. You should not
         modify this data member directly from derived classes. For
         reading the value of this data member, please use "isRunning()"
         since "runs" will probably be made private in later versions
         of KProcess.
      */
      bool runs;

      /**
          The PID of the currently running process (see "getPid()").
          You should not modify this data member in derived classes.
          Please use "getPid()" instead of directly accessing this
          member function since it will probably be made private in
          later versions of KProcess.
      */
      pid_t pid_;

      /** The process' exit status as returned by "waitpid". You should not
          modify the value of this data member from derived classes. You should
          rather use @ref exitStatus than accessing this data member directly
          since it will probably be made private in further versions of
          KProcess.
      */
      int status;

      /** See setRunPrivileged()
      */
      bool keepPrivs;

      /*
    	Functions for setting up the sockets for communication.
    	setupCommunication
    	-- is called from "start" before "fork"ing.
    	commSetupDoneP
    	-- completes communcation socket setup in the parent
    	commSetupDoneC
    	-- completes communication setup in the child process
    	commClose
    	-- frees all allocated communication ressources in the parent
    	after the process has exited
      */

      /**
        This function is called from "KProcess::start" right before a "fork" takes
        place. According to
        the "comm" parameter this function has to initialize the "in", "out" and
        "err" data member of KProcess.

        This function should return 0 if setting the needed communication channels
        was successful.

        The default implementation is to create UNIX STREAM sockets for the communication,
        but you could overload this function and establish a TCP/IP communication for
        network communication, for example.
      */
      virtual int setupCommunication(Communication comm);

      /**
         Called right after a (successful) fork on the parent side. This function
         will usually do some communications cleanup, like closing the reading end
         of the "stdin" communication channel.

         Furthermore, it must also create the QSocketNotifiers "innot", "outnot" and
         "errnot" and connect their Qt slots to the respective KProcess member functions.

         For a more detailed explanation, it is best to have a look at the default
         implementation of "setupCommunication" in @ref kprocess.cpp.
      */
      virtual int commSetupDoneP();

      /**
         Called right after a (successful) fork, but before an "exec" on the child
         process' side. It usually just closes the unused communication ends of
         "in", "out" and "err" (like the writing end of the "in" communication
         channel.
      */
      virtual int commSetupDoneC();

      /**
         Immediately called after a process has exited. This function normally
         calls commClose to close all open communication channels to this
         process and emits the "processExited" signal (if the process was
         not running in the "DontCare" mode).
      */
      virtual void processHasExited(int state);

      /**
         Should clean up the communication links to the child after it has
         exited. Should be called from "processHasExited".
      */
      virtual void commClose();

      /**
       * the socket descriptors for stdin/stdout/stderr.
       */
      int out[2];
      int in[2];
      int err[2];

      /**
       * The socket notifiers for the above socket descriptors.
       */
      QSocketNotifier *innot;
      QSocketNotifier *outnot;
      QSocketNotifier *errnot;

      /**
         Lists the communication links that are activated for the child
         process.  Should not be modified from derived classes.
      */
      Communication communication;

      /**
         Called by "slotChildOutput" this function copies data arriving from the
         child process's stdout to the respective buffer and emits the signal
         "@ref receivedStderr".
      */
      int childOutput(int fdno);

      /**
         Called by "slotChildOutput" this function copies data arriving from the
         child process's stdout to the respective buffer and emits the signal
         "@ref receivedStderr"
      */
      int childError(int fdno);

      // information about the data that has to be sent to the child:

      const char *input_data;  // the buffer holding the data
      int input_sent;    // # of bytes already transmitted
      int input_total;   // total length of input_data

      /**
        @ref KProcessController is a friend of KProcess because it has to have
        access to various data members.
      */
      friend class KProcessController;

    private:
      // Disallow assignment and copy-construction
      KProcess( const KProcess& );
      KProcess& operator= ( const KProcess& );

      KProcessPrivate *d;
    };

    class KShellProcessPrivate;

    /**
    * This class is similar to @ref KProcess. The only difference is that
    * KShellProcess runs the specified executable through a UN*X shell so
    * that standard shell mechanisms like wildcard matching, use of pipes
    * and environment variable expansion will work.

    * For example, you could run commands like the following through
    * KShellProcess:

    * <pre>
    *   ls ~/HOME/ *.lyx | sort | uniq |wc -l
    * </pre>

    * KShellProcess tries really hard to find a valid executable shell. Here
    * is the algorithm used for finding an executable shell:

    *    @li Try the executable pointed to by the "SHELL" environment
    *    variable with whitespaces stripped off

    *    @li If your process runs with uid != euid or gid != egid, a shell
    *    not listed in /etc/shells will not used.

    *    @li If no valid shell could be found, "/bin/sh" is used as a last resort.

    *   @short A class derived from @ref KProcess to start child
    *   	processes through a shell.
    *   @author Christian Czezakte <e9025461@student.tuwien.ac.at>
    *   @version $Id: kprocess.h,v 1.35 2000/09/23 22:25:03 faure Exp $
    */
    class KShellProcess: public KProcess
    {
      Q_OBJECT

    public:

      /**
          Constructor

          By specifying the name of a shell (like "/bin/bash") you can override
          the mechanism for finding a valid shell as described in the detailed
          description of this class.
      */
      KShellProcess(const char *shellname=0);

      /**
       * Descructor.
       */
      ~KShellProcess();

      /**
        Starts up the process. -- For a detailed description
        have a look at the "start" member function and the detailed
        description of @ref KProcess .
      */
      virtual bool start(RunMode  runmode = NotifyOnExit,
    		  Communication comm = NoCommunication);

      /**
       * This function can be used to quote an argument string such that
       * the shell processes it properly. This is e. g. necessary for
       * user-provided file names which may contain spaces or quotes.
       * It also prevents expansion of wildcards and environment variables.
       */
      static QString quote(const QString &arg);

    private:

      /**
       * Searches for a valid shell. See the general description of this
       * class for information on how the search is actually performed.
      */
      QCString searchShell();

      /**
       * Used by @ref searchShell in order to find out whether the shell found
       * is actually executable at all.
      */
      bool isExecutable(const QCString &filename);

      QCString shell;

      // Disallow assignment and copy-construction
      KShellProcess( const KShellProcess& );
      KShellProcess& operator= ( const KShellProcess& );

      KShellProcessPrivate *d;
    };

    #endif