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tcl/tk process?

Posted on 2002-05-15
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Last Modified: 2013-11-22
Hi,

I am looking for another solution of how to bring an execution of my tcl/tk programme into background besides doing
> prog input &

I want it to be done from within my program "prog" itself i.e.
> prog input
will do the job and I can use this tty to other thing without having to do
Control-Z & bg.

Thanx.
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Question by:mafendee
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by:ahoffmann
Comment Utility
if {[string compare $argv {deamon}] == 0} {
  # process goes here
} else {
   exec $argv0 deamon &
   exit
}
exit
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Author Comment

by:mafendee
Comment Utility
I dont really understand how it should work. My first question, what is deamon, are u referring to "input" from

> prog input

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Author Comment

by:mafendee
Comment Utility
I dont really understand how it should work. My first question, what is deamon, are u referring to "input" from

> prog input

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by:ahoffmann
Comment Utility
simply use my suggestion as first lines in your "prog"'s file, that's it.
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Author Comment

by:mafendee
Comment Utility
Basically I wanna know what am I doing. It will be very nice if you could drop a few lines concerning what this code actually does. I was a bit confused with its input parameter.
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LVL 51

Expert Comment

by:ahoffmann
Comment Utility
the code actually checks the first command line parameter, if it is not equal "daemon" the script starts itself in background and exits.
Think that was what you want.
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Author Comment

by:mafendee
Comment Utility
I have tried with your suggestion, but still with some problems...
1. should it be daemon or deamon (in your code)?

If I understood correct, I have done it this way,

if {[string compare $argv {deamon}] == 0} {
       # process goes here   ### A
} else {
       exec $argv0 deamon &  ### B
       exit
}
exit                     ### C

line A: process goes here means all my written code should be placed there, right?

line B: what happen to my command line parameter 'input' from > prog input ?

line C: I am not sure whether I need this 'exit' because it will exit the whole program.
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by:ahoffmann
Comment Utility
1. the typo dosn't matter 'cause deamon is a string which I typed equal both times (even I meant daemon:-)

line A: right

line B: use changed code

set d [lindex $argv 0]
if {[string compare $d {deamon}] == 0} {
   set argv [lreplace $argv 0 0 {}]
   # process goes here
} else {
   exec $argv0 deamon $argv &
   exit
}
exit

line C: defensive programming (in case of something goes wrong)
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Author Comment

by:mafendee
Comment Utility
I see what you meant. I have changed the code, I think you wanted to delete deamon out from this line.
       set argv [lreplace $argv 0 0 {}]
I works better when I change it to
       set argv [lreplace $argv 0 0]
otherwise it will change argv to "{} input".

But, the problem now is that, it is still doesn't work.

If I exclude line C then, the program exit.
If I include line C, two processes were created and the
process still in foreground, no access to terminal still.

Then I include line D
#######################################################
} else {
        catch {exec $argv0 deamon $argv &}
        catch {exec kill [pid] 2>& /dev/null} ### line D
     exit
}
#######################################################
It seems to solve the problem, i.e. start program in background and able to access the terminal for other use.

BUT (hopefully, this is the last problem) at the terminal I have this "Terminated" message. It doesn't seem good if other user use this program.
###########################
sun100 > prog input
Terminated
###########################
I have tried with the /dev/null upthere but it still doesn't work. Any clue?

One more thing, I am using "wish" as my interpreter
#/opt/tools/sun5/bin/wish -f
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Accepted Solution

by:
ahoffmann earned 50 total points
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wish is ok, 'cause we only use tcl commands which are a subset of wish. I used wish too for my tests ;-)

Are you shure about your "include" and "exclude" statement? is it not the other way around?

For me it works exactly as I posted it here. I don't need catch.
'cause you need to use catch, it sounds like your shell (wish or its parent) is not able to start programs in background. Wired.
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Author Comment

by:mafendee
Comment Utility
You are right, the "include" and "exclude" things should work the other way round. Anyway, it works good right now.
thanx.
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