From

https://sourceforge.net/tracker/index.php?func=detail&aid=1656350&group_id=13247&atid=313247

	-mi

*** doc/TclX.n	2004-11-22 16:58:20.000000000 -0500
--- doc/TclX.n	2009-03-14 23:41:19.000000000 -0400
***************
*** 221,226 ****
--- 221,234 ----
  \fBwait\fR command has full functionality.  \fB0\fR if the \fBwait\fR
  command has limited functionality.
  .TP
+ \fBhave_getsid\fR
+ Return \fB1\fR if the \fBgetsid\fR system call is available.
+ If it is, the \fBid process session\fR command may be used.
+ .TP
+ \fBhave_setsid\fR
+ Return \fB1\fR if the \fBsetsid\fR system call is available.
+ If it is, the \fBid process session set\fR command may be used.
+ .TP
  \fBappname\fR
  Return the symbolic application name of the current application linked with
  the Extended Tcl library.  The C variable \fBtclAppName\fR must be set by the
***************
*** 736,741 ****
--- 744,755 ----
  \fBid process group set\fR
  Set the process group ID of the current process to its process ID.
  .TP
+ \fBid process session\fR
+ Return the session ID of the current process.
+ .TP
+ \fBid process session set\fR
+ Set the process session ID of the current process to be a session leader.
+ .TP
  \fBid host\fR
  Returns the standard host name of the machine the process is executing on.
  .IP
*** generic/tclXgeneral.c	Mon May  7 13:16:47 2001
--- generic/tclXgeneral.c	Sun Oct 14 17:54:28 2001
***************
*** 274,279 ****
--- 274,295 ----
  #       endif        
          return TCL_OK;
      }
+     if (STREQU ("have_getsid", optionPtr)) {
+ #       if (!defined(NO_GETSID)) && (!defined(WIN32))
+         Tcl_SetBooleanObj (resultPtr, TRUE);
+ #       else
+         Tcl_SetBooleanObj (resultPtr, FALSE);
+ #       endif        
+         return TCL_OK;
+     }
+     if (STREQU ("have_setsid", optionPtr)) {
+ #       if (!defined(NO_SETSID)) && (!defined(WIN32))
+         Tcl_SetBooleanObj (resultPtr, TRUE);
+ #       else
+         Tcl_SetBooleanObj (resultPtr, FALSE);
+ #       endif        
+         return TCL_OK;
+     }
      if (STREQU ("appname", optionPtr)) {
          if (tclAppName != NULL) {
              Tcl_SetStringObj (resultPtr, tclAppName, -1);
***************
*** 302,307 ****
--- 318,324 ----
                            "have_fchown, have_fchmod, have_flock, ",
                            "have_fsync, have_ftruncate, have_msgcats, ",
                            "have_symlink, have_truncate, ",
+                           "have_getsid, have_setsid, ",
                            "have_posix_signals, have_waitpid, appname, ",
                            "applongname, appversion, or apppatchlevel",
                            (char *) NULL);
*** unix/tclXunixId.c	Thu Dec  2 20:02:08 1999
--- unix/tclXunixId.c	Fri Oct 12 15:09:13 2001
***************
*** 133,138 ****
--- 133,140 ----
   *        id process parent
   *        id process group
   *        id process group set
+  *        id process session
+  *        id process session set
   *
   *        id effective user
   *        id effective userid
***************
*** 317,323 ****
  }
  
  /*
!  * id process ?parent|group? ?set?
   */
  static int
  IdProcess (interp, objc, objv)
--- 319,325 ----
  }
  
  /*
!  * id process ?parent|group|session? ?set?  
   */
  static int
  IdProcess (interp, objc, objv)
***************
*** 332,338 ****
      if (objc > 4)
          return TclX_WrongArgs (interp, 
  			       objv [0], 
! 			       "process ?parent|group? ?set?");
  
      if (objc == 2) {
  	Tcl_SetObjResult (interp, Tcl_NewIntObj (getpid ()));
--- 334,340 ----
      if (objc > 4)
          return TclX_WrongArgs (interp, 
  			       objv [0], 
! 			       "process ?parent|group|session? ?set?");
  
      if (objc == 2) {
  	Tcl_SetObjResult (interp, Tcl_NewIntObj (getpid ()));
***************
*** 373,381 ****
  #endif
          return TCL_OK;
      }
  
!     TclX_AppendObjResult (interp, "expected one of \"parent\" or \"group\" ",
!                           "got\"", subCommand, "\"", (char *) NULL);
      return TCL_ERROR;
  }
  
--- 375,410 ----
  #endif
          return TCL_OK;
      }
+     if (STREQU (subCommand, "session")) {
+         if (objc == 3) {
+ #ifndef NO_GETSID
+ 	    Tcl_SetObjResult (interp, Tcl_NewIntObj (getsid (0)));
+ #endif
+             return TCL_OK;
+         }
+ 	trailerCommand = Tcl_GetStringFromObj (objv[3], NULL);
+         if ((objc != 4) || !STREQU (trailerCommand, "set"))
+             return TclX_WrongArgs (interp, objv [0], 
+                               " process session ?set?");
+ 
+         if (Tcl_IsSafe (interp)) {
+             TclX_AppendObjResult (interp,  "can't set process session from a ",
+                                   "safe interpeter", (char *) NULL);
+             return TCL_ERROR;
+         }
+ #ifndef NO_SETSID
+ 	if (setsid () == -1 ) {
+ 	    TclX_AppendObjResult (interp,  "session set failed, process is ",
+ 				"already session leader", (char *) NULL);
+             return TCL_ERROR;
+ 	}
+ 	return TCL_OK;
+ #endif
+     }
  
!     TclX_AppendObjResult (interp, "expected one of \"parent\", \"group\" ",
!                           "or \"session\" ",
!                           "got \"", subCommand, "\"", (char *) NULL);
      return TCL_ERROR;
  }