Question

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In Linux, how to prevent a background process from being stopped after closing SSH client

I have a C program which I access and interact with over terminal (usually from SSH on a linux box). I have been trying to find the solution to the problem where after I close the terminal/logout, the process ends with it (the program basically asks for some options then goes about its business with no further interaction required so I would like to have it continue to run even after I logout of SSH).

There are ways in linux to avoid this such as ‘screen’, but I want to do it programatically with C without relying on installed packages such as screen- even if this means reinventing the wheel.

So far I understand fork() to be the standard trivial way to daemonize a process, so could anyone help me to finish the code that allows the above described process to happen?

Within parent:

 main()
{

//Do interactive stuff

signal(SIGCHLD, SIG_IGN); //stops the parent waiting for the child process to end

if(fork())
 exit(0);
// and now the program continues in the child process

I can now logout of SSH which closes the original shell…and the child continues its work!

Within child:

//Continue with processing data/whatever the program does (no input/output to terminal required)
exit(0);

Answer 1

to detach the process from the parent:

use setsid() on the children process, it will run the program in new session

 sid = setsid();

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To Keep a program running even when the terminal is closed:

SIGHUP is a signal sent to a process when its controlling terminal is closed.

try to ignore it using

signal (SIGHUP, SIG_IGN);