Linux process in background – “Stopped” in jobs?

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In Linux and other Unix systems, a job that is running in the background, but still has its stdin (or std::cin) associated with its controlling terminal (a.k.a. the window it was run in) will be sent a SIGTTIN signal, which by default causes the program to be completely stopped, pending the user bringing it to the foreground (fg %job or similar) to allow input to actually be given to the program. To avoid the program being paused in this way, you can either:

  1. Make sure the programs stdin channel is no longer associated with the terminal, by either redirecting it to a file with appropriate contents for the program to input, or to /dev/null if it really doesn’t need input – e.g. myprogram < /dev/null &.
  2. Exit the terminal after starting the program, which will cause the association with the program’s stdin to go away. But this will cause a SIGHUP to be delivered to the program (meaning the input/output channel experienced a “hangup”) – this normally causes a program to be terminated, but this can be avoided by using nohup – e.g. nohup myprogram &.

If you are at all interested in capturing the output of the program, this is probably the best option, as it prevents both of the above signals (as well as a couple others), and saves the output for you to look at to determine if there are any issues with the programs execution:

nohup myprogram < /dev/null > ${HOME}/myprogram.log 2>&1 &

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