'''execx - EXECuting transparently out of the VFS of a starkit/starpack'''

The following simplifies the execution of .EXEs which are inside of a Starkits/Starpacks VFS by transparently copying them ot of the VFS to a temporary location and EXECing them from there (just as it already works from the tcl core with LOADing DLLs). I pack various external tools needed by my scripts in the VFS because it's not always clear, if the machine the script is later running on has such tools installed in the path or if the tool-versions are correct. So it's safer to deliver the tools right within the script and to make a temp copy out of the VFS and call them from there. However, the default is to use an external available tool (to save the copy step).

Todo/Notes:

   * the code just has to be more generalized, reviewed and documented, but it already works...
   * make the VFS-source-location a parameter
   * make the temporary-destination-location a parameter, at least more robust (%temp% may not exist everywhere or may not be writable...)
   * add errorhandling
   * see sourcecode for additional comments and ideas

 # execx.tcl, M.Hoffmann 2003-2004

 package provide execx 1.1

 #----------------------------------------------------------------------------------

 namespace eval execx {
      variable running     ; #
      variable exectrace 0 ; # 1: display on stdout what's going on
      variable force 0     ; # 1: force use of the VFS-internal program, (if 0, look
                           ; # first if an external program is available and use
                           ; # internal copy only, if no external found)
 }

 #----------------------------------------------------------------------------------
 # a little wrapping...
 proc execx::setforce {setting} {
      set execx::force $setting
 }
 proc execx::settrace {setting} {
      set execx::exectrace $setting
 }
 proc execx::gettemps {} {
      return [array get running]; # untested so far
 }

 #----------------------------------------------------------------------------------
 # args - same format of parameters as in the original EXEC-command (I hope...)
 # return - same as EXEC (again, I hope...)
 # remarks - if a program es executed in the background with &, the temporary copy
 #  is not removed, because at least on win32 it is locked. For this reason, to help
 #  the caller to do this later, the namespace array execx::running is populated
 #  with the names of the temporary program copies (the keys are the PIDs)
 #
 proc execx::execx1 {args} {
      variable running
      set progIdx -1
      set force   -1
      # locate the programspec in the exec-cmd
      foreach a $args {
              incr progIdx
              if {$a != "-keepnewline" && $a != "--"} {
                 break;
              }
      }
      set progCallOrg [lindex $args $progIdx]
      set progCallTst {}
      set progCallNew {}
      if {!$::execx::force} {
         # search for external callable program
         set progCallTst [auto_execok $progCallOrg]
      }
      if {[string equal $progCallTst ""]} {
         # no external program available, or 'force' specified
         # I alway use the tools-Subdirectory in my starpacks for standaloneprograms:
         set toolDir     [file join [file dirname [info script]] .. tools]
         set progName    [file tail $progCallOrg]
         set progCallNew [file join $::env(temp) $progName]; # critical, see notes
         catch {file copy -force -- [file join $toolDir $progName] $progCallNew}; # missing error-return...
         lset args $progIdx [list $progCallNew]
      }
      if {$execx::exectrace} {
         puts -nonewline {>>> }
         puts $args
      }
      catch {eval exec $args} rc; # Question: is UPLEVEL more suitable?????
      if {$progCallNew != ""} {
         if {[lindex $args end] != "&"} {
            # on can add an switch for -nodeltemp, if required
            catch {file delete -force -- $progCallNew}
         } else {
            # see notes
            set running($rc) $progCallNew
         }
      }
      return $rc
 }
----
[Category Tclkit]