Mark a process and its (future) child tree
ps_mark_tree() generates a random environment variable name and sets
it in the current R process. This environment variable will be (by
default) inherited by all child (and grandchild, etc.) processes, and
will help finding these processes, even if and when they are (no longer)
related to the current R process. (I.e. they are not connected in the
ps_kill_tree(marker, sig = signals()$SIGKILL)
R expression to evaluate in the new context.
String scalar, the name of the environment variable to use to find the marked processes.
The signal to send to the marked processes on Unix. On Windows this argument is ignored currently.
ps_find_tree() finds the processes that set the supplied environment
variable and returns them in a list.
ps_kill_tree() finds the processes that set the supplied environment
variable, and kills them (or sends them the specified signal on Unix).
with_process_cleanup() evaluates an R expression, and cleans up all
external processes that were started by the R process while evaluating
the expression. This includes child processes of child processes, etc.,
recursively. It returns a list with entries:
result is the result of
visible is TRUE if the expression should be printed
to the screen, and
process_cleanup is a named integer vector of the
cleaned pids, names are the process names.
expr throws an error, then so does
same error. Nevertheless processes are still cleaned up.
ps_mark_tree() returns the name of the environment variable,
which can be used as the
ps_find_tree() returns a list of
ps_kill_tree() returns the pids of the killed processes, in a named
integer vector. The names are the file names of the executables, when
with_process_cleanup() returns the value of the evaluated expression.
with_process_cleanup() is problematic if the R process is
multi-threaded and the other threads start subprocesses.
with_process_cleanup() cleans up those processes as well, which is
probably not what you want. This is an issue for example in RStudio.
Do not use
with_process_cleanup(), unless you are sure that the
R process is single-threaded, or the other threads do not start
subprocesses. E.g. using it in package test cases is usually fine,
because RStudio runs these in a separate single-threaded process.
The same holds for manually running
ps_mark_tree() and then