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Old 06-29-2009, 05:47 AM   #1
Gachl
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Sending text to process


Hi!
I have some TF2 servers running in a screen, now I want to create a little script that sends a specific text to all of these servers. Now finding the PID etc isn't a problem, more the sending text to process. How do I do that?

eg.
Code:
for PID in `pgrep -x srcds_run`; do $PID < "sm_reloadadmins\n"; done

Last edited by Gachl; 06-29-2009 at 05:57 AM. Reason: changed example
 
Old 06-29-2009, 05:57 AM   #2
david1941
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You might investigate named pipes: http://www.linuxjournal.com/content/...pes-fifos-bash
 
Old 06-29-2009, 05:59 AM   #3
Gachl
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how would I make the process read the pipe?
 
Old 06-29-2009, 06:06 AM   #4
david1941
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Have the receiving process read the pipe; it will block waiting for the input. When data is written, the receiving process will read it and take whatever action is coded.
 
Old 06-29-2009, 06:13 AM   #5
Gachl
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Well, I still have to write in the process itself
The TF2 server is basically a foreground application for the console where I can type commands and it executes it on the server (eg. I type status and it writes the current server status).
now if I use this:
Code:
./start_server_cp < serverfifo
I won't see any IO of the server's console.

edit: no thats wrong, the process simply stopps until something is in serverfifo..

Last edited by Gachl; 06-29-2009 at 06:16 AM.
 
Old 06-29-2009, 07:17 AM   #6
david1941
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If you just need a state indication, you could do something like this:
Code:
until [ -f /tmp/something ]; do echo hi; done;
and write the flag flie like this from another process:
Code:
touch /tmp/something
That way the flag fle could be used to control as many processes as you wish.

Last edited by david1941; 06-29-2009 at 07:18 AM. Reason: correct code tags
 
Old 06-29-2009, 09:20 AM   #7
Gachl
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This is WAY too complex..
Is there a way of mapping the stdin of a process to two sources, which would be in my case my keyboard and my named pipe? (And of course stdout to the console). And all this without blocking.
 
Old 06-29-2009, 09:27 AM   #8
pixellany
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Quote:
Originally Posted by Gachl View Post
Is there a way of mapping the stdin of a process to two sources, which would be in my case my keyboard and my named pipe?
Assuming that this IS possible, it does not sound like a very good idea.......How would the process know which source to pay attention to?
 
Old 06-29-2009, 09:33 AM   #9
Gachl
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Good point.
I also could set my pipe as stdin and stdout and then use some kind of weird contraption of tee and tail -f to read+write the servers I/O.
But for some reason
Code:
./start_server_testing <> serverfifo
doesn't write the servers output to the serverfifo *confused*.

Edit: assuming multiple input sources are possible the process can mix the two because I am 1000% sure, if something writes to the pipe nothing is written to the console. So I think this wouldnt cause any trouble.

Edit2: Damn this can't be so hard to send text to a process. Linux is so powerful, this should be a damn small task for it

Last edited by Gachl; 06-29-2009 at 09:39 AM.
 
Old 06-29-2009, 12:04 PM   #10
pixellany
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Quote:
Originally Posted by Gachl View Post
Edit2: Damn this can't be so hard to send text to a process. Linux is so powerful, this should be a damn small task for it
I did not attempt to understand the details, but the advice offered by @david1941 did not seem all that complex....In fact, I must go back and thank him for getting into my thick head what a "named pipe" is.....
 
Old 06-30-2009, 03:39 AM   #11
Gachl
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Quote:
Originally Posted by pixellany View Post
I did not attempt to understand the details, but the advice offered by @david1941 did not seem all that complex....In fact, I must go back and thank him for getting into my thick head what a "named pipe" is.....
agree. But I don't want to run an additional script if I start the server just to get the pipe work.

Also why isn't program <> pipe writing stdout to the pipe? I still can see all console output and the pipe remains empty.
 
  


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