On 21 September 2010 06:06, Joachim Breitner wrote:

Hi,

I just noticed this in my process list:

 │           ├─xmonad-x86_64-l  │           │   └─sh -c gnome-terminal  │           │       └─gnome-terminal

and the reason is here, in Core.hs:

-- | Like 'spawn', but returns the 'ProcessID' of the launched application spawnPID :: MonadIO m => String -> m ProcessID spawnPID x = io . forkProcess . finally nullStdin $ do                uninstallSignalHandlers                createSession                executeFile "/bin/sh" False ["-c", x] Nothing  where    nullStdin = do        fd <- openFd "/dev/null" ReadOnly Nothing defaultFileFlags        dupTo fd stdInput        closeFd fd

Generally, this is of course useful. But I bet that most commands passed to spawn are simple program names without arguments or any fancy shell-related stuff. Executing a shell here seems overkill. Not much, but still avoidable.

I believe the reason here is to do a double fork, such that when xmonad restarts the program you launched via xmonad isn't killed. -- Ivan Lazar Miljenovic Ivan.Miljenovic@gmail.com IvanMiljenovic.wordpress.com

Joachim Breitner writes:

-- | Like 'spawn', but returns the 'ProcessID' of the launched application spawnPID :: MonadIO m => String -> m ProcessID spawnPID x = io . forkProcess . finally nullStdin $ do uninstallSignalHandlers createSession executeFile "/bin/sh" False ["-c", x] Nothing

Generally, this is of course useful. But I bet that most commands passed to spawn are simple program names without arguments or any fancy shell-related stuff. Executing a shell here seems overkill. Not much, but still avoidable.

How about checking whether the argument x contains only alphanumerical characters and, if that is the case, executing the program directly? Such short-circuit logic is for example also used by perl’s sytem(), see perldoc -f system:

I'm not a big fan of perl's all-implicit behaviour. I'd rather rename spawn(PID) to spawnShell(PID) x = spawn(PID) "/bin/sh" ["-c", x] and make the shell invocation explicit. If such incompatible change is impossible, then make it spawn(PID) x = execute(PID) "/bin/sh" ["-c", x] or similar. Meanwhile, use exec to get rid of the shell process. :) -- Regards, Feri.