When a session leader acquires a controlling terminal, how would the other existing processes in the session also acquire the controlling terminal?

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Suppose there is a session with multiple processes in it and without a controlling terminal.



When the session leader creates a connection to a controlling terminal,



  • how would the other processes in the same session learn that the session has a controlling terminal and


  • how could they also make use of the controlling terminal?


The reason that I have this question is the following. Usually a process calls setsid() to start a new session and become its leader, and calls open() to connect to a controlling terminal. Then the session leader goes on to fork() child processes, and the children will inherit the file descriptor to the controlling terminal.



I then wonder what if a session already has multiple processes and but has no controlling terminal, and then the leader creates a connection to a controlling terminal, and then what about the other processes in the session.



Thanks.




linux session controlling-terminal




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    up vote
    -1
    down vote

    favorite












    Suppose there is a session with multiple processes in it and without a controlling terminal.



    When the session leader creates a connection to a controlling terminal,



    • how would the other processes in the same session learn that the session has a controlling terminal and


    • how could they also make use of the controlling terminal?


    The reason that I have this question is the following. Usually a process calls setsid() to start a new session and become its leader, and calls open() to connect to a controlling terminal. Then the session leader goes on to fork() child processes, and the children will inherit the file descriptor to the controlling terminal.



    I then wonder what if a session already has multiple processes and but has no controlling terminal, and then the leader creates a connection to a controlling terminal, and then what about the other processes in the session.



    Thanks.




    linux session controlling-terminal




    share|improve this question





















      up vote
      -1
      down vote

      favorite









      up vote
      -1
      down vote

      favorite











      Suppose there is a session with multiple processes in it and without a controlling terminal.



      When the session leader creates a connection to a controlling terminal,



      • how would the other processes in the same session learn that the session has a controlling terminal and


      • how could they also make use of the controlling terminal?


      The reason that I have this question is the following. Usually a process calls setsid() to start a new session and become its leader, and calls open() to connect to a controlling terminal. Then the session leader goes on to fork() child processes, and the children will inherit the file descriptor to the controlling terminal.



      I then wonder what if a session already has multiple processes and but has no controlling terminal, and then the leader creates a connection to a controlling terminal, and then what about the other processes in the session.



      Thanks.




      linux session controlling-terminal




      share|improve this question











      Suppose there is a session with multiple processes in it and without a controlling terminal.



      When the session leader creates a connection to a controlling terminal,



      • how would the other processes in the same session learn that the session has a controlling terminal and


      • how could they also make use of the controlling terminal?


      The reason that I have this question is the following. Usually a process calls setsid() to start a new session and become its leader, and calls open() to connect to a controlling terminal. Then the session leader goes on to fork() child processes, and the children will inherit the file descriptor to the controlling terminal.



      I then wonder what if a session already has multiple processes and but has no controlling terminal, and then the leader creates a connection to a controlling terminal, and then what about the other processes in the session.



      Thanks.





      linux session controlling-terminal





      share|improve this question










      share|improve this question




      share|improve this question









      asked May 29 at 16:06









      Tim

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      22.6k61222401




















          1 Answer
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          Any new child the session leader creates after it acquired a controlling terminal will also have that controlling terminal. A controlling terminal is something that is inherited from the parent.



          In other words: existing children are not affected.






          share|improve this answer























          • Thanks. But I was asking about the already existing children instead of any future children, when the leader acquires a controlling terminal.
            – Tim
            May 29 at 16:33










          • OK, I enhanced the answer.
            – schily
            May 29 at 16:50










          • Thanks. What do you mean by " existing children are not affected"? The other processes in the same session are not necessarily children of the session leader. How could the other processes learn that the session has a controlling terminal and also open the controlling terminal as a file descriptor?
            – Tim
            Jun 1 at 19:17











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          1 Answer
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          up vote
          0
          down vote













          Any new child the session leader creates after it acquired a controlling terminal will also have that controlling terminal. A controlling terminal is something that is inherited from the parent.



          In other words: existing children are not affected.






          share|improve this answer























          • Thanks. But I was asking about the already existing children instead of any future children, when the leader acquires a controlling terminal.
            – Tim
            May 29 at 16:33










          • OK, I enhanced the answer.
            – schily
            May 29 at 16:50










          • Thanks. What do you mean by " existing children are not affected"? The other processes in the same session are not necessarily children of the session leader. How could the other processes learn that the session has a controlling terminal and also open the controlling terminal as a file descriptor?
            – Tim
            Jun 1 at 19:17















          up vote
          0
          down vote













          Any new child the session leader creates after it acquired a controlling terminal will also have that controlling terminal. A controlling terminal is something that is inherited from the parent.



          In other words: existing children are not affected.






          share|improve this answer























          • Thanks. But I was asking about the already existing children instead of any future children, when the leader acquires a controlling terminal.
            – Tim
            May 29 at 16:33










          • OK, I enhanced the answer.
            – schily
            May 29 at 16:50










          • Thanks. What do you mean by " existing children are not affected"? The other processes in the same session are not necessarily children of the session leader. How could the other processes learn that the session has a controlling terminal and also open the controlling terminal as a file descriptor?
            – Tim
            Jun 1 at 19:17













          up vote
          0
          down vote










          up vote
          0
          down vote









          Any new child the session leader creates after it acquired a controlling terminal will also have that controlling terminal. A controlling terminal is something that is inherited from the parent.



          In other words: existing children are not affected.






          share|improve this answer















          Any new child the session leader creates after it acquired a controlling terminal will also have that controlling terminal. A controlling terminal is something that is inherited from the parent.



          In other words: existing children are not affected.







          share|improve this answer















          share|improve this answer



          share|improve this answer








          edited May 29 at 16:42


























          answered May 29 at 16:20









          schily

          8,63821435




          8,63821435











          • Thanks. But I was asking about the already existing children instead of any future children, when the leader acquires a controlling terminal.
            – Tim
            May 29 at 16:33










          • OK, I enhanced the answer.
            – schily
            May 29 at 16:50










          • Thanks. What do you mean by " existing children are not affected"? The other processes in the same session are not necessarily children of the session leader. How could the other processes learn that the session has a controlling terminal and also open the controlling terminal as a file descriptor?
            – Tim
            Jun 1 at 19:17

















          • Thanks. But I was asking about the already existing children instead of any future children, when the leader acquires a controlling terminal.
            – Tim
            May 29 at 16:33










          • OK, I enhanced the answer.
            – schily
            May 29 at 16:50










          • Thanks. What do you mean by " existing children are not affected"? The other processes in the same session are not necessarily children of the session leader. How could the other processes learn that the session has a controlling terminal and also open the controlling terminal as a file descriptor?
            – Tim
            Jun 1 at 19:17
















          Thanks. But I was asking about the already existing children instead of any future children, when the leader acquires a controlling terminal.
          – Tim
          May 29 at 16:33




          Thanks. But I was asking about the already existing children instead of any future children, when the leader acquires a controlling terminal.
          – Tim
          May 29 at 16:33












          OK, I enhanced the answer.
          – schily
          May 29 at 16:50




          OK, I enhanced the answer.
          – schily
          May 29 at 16:50












          Thanks. What do you mean by " existing children are not affected"? The other processes in the same session are not necessarily children of the session leader. How could the other processes learn that the session has a controlling terminal and also open the controlling terminal as a file descriptor?
          – Tim
          Jun 1 at 19:17





          Thanks. What do you mean by " existing children are not affected"? The other processes in the same session are not necessarily children of the session leader. How could the other processes learn that the session has a controlling terminal and also open the controlling terminal as a file descriptor?
          – Tim
          Jun 1 at 19:17













           

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