TProcess weird behavior on Linux, urgent help needed!
lazarus / 32-Linux

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ggallo · 2013-11-08 12:31

Hi All!

I have a weird problem with TProcess on Linux, and I can't find any
solution.

I wrote an application that uses some self update as follows: the main
application checks if update available, downloads it and starts the
included update program. If update program started, the main
application quits to let the update program change files and so. This
works very well on Windows, updater started, main application quits,
files replaced, main application restarted by updater program.

But on Linux, the updater started, but immediately ended when
TProcess.Free called on main application exit.

I can't find any solution to keep the program running - started by
TProcess - after TProcess.Free.

Can anyone help me?

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marcov · 2013-11-08 23:22

Afaik under *nix, processes remain part of their parents process tree.
Kill the parent, kill the process tree.

To fix this is called "daemonization", roughly the same way a daemon
(equivalent to a service on windows) is created. So probably the
updater program should at least partially daemonize itself. There is a
daemonizing program in the FPC demos.

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Yogi · 2013-11-09 00:12

marcov is right. Your updater program is killed when the program which
started it is ending.
On Linux You can start your updater via "nohup" to avoid this.
Google for "nohup"
(nohup => the "hangup"-Signal will be ignored)

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ggallo · 2013-11-09 00:24

Thanks for the answers marcov and Yogi!

I will look at the "daemonization" demo tomorrow, maybe it will help
me solve this problem.

I already fount "nohup" today, but unfortunately it not work with user
right elevation.
If I start my updater with "nohup updater -option -option" the
solution works, updater run after main app exit. Good.
But if I run "nohup pkexec updater -option..." then this combo also
killed with main app, as before. So I can't copy to program's install
dir (it's created root:root). To be correct, standalone "pkexec
updater ..." also not working, so this is not nohup's fault.

I'll write here if I solve this somehow, to let others read it.