$signal() and $interrupt() now use the process group

NEWS.md

@@ -1,5 +1,11 @@
 # processx (development version)
 
+* The `$signal()` and `$interrupt()` methods now send the signal to the
+  child's whole process group by default on Unix. This matches the
+  behavior of `$kill()`. A new `group` argument (default `TRUE`) can be
+  set to `FALSE` to send the signal to the child process only. The
+  argument is ignored on Windows.
+
 * The `grace` argument of the `kill()` method is now active on Unix
   platforms. processx first tries to kill with `SIGTERM` with a
   timeout of `grace` seconds. After the timeout, `SIGKILL` is sent as

R/process.R

@@ -355,16 +355,28 @@ process <- R6::R6Class(
     #' and the 0 signal as well.
     #' @param signal An integer scalar, the id of the signal to send to
     #'   the process. See [tools::pskill()] for the list of signals.
-
-    signal = function(signal) process_signal(self, private, signal),
+    #' @param group Whether to send the signal to the whole process group of
+    #'   the child. The child is started in its own process group (via
+    #'   `setsid()` on Unix), so by default the signal is delivered to the
+    #'   child and any descendants that have not started a new group of
+    #'   their own. Set to `FALSE` to send the signal to the child process
+    #'   only. Ignored on Windows.
+
+    signal = function(signal, group = TRUE) {
+      process_signal(self, private, signal, group)
+    },
 
     #' @description
     #' Send an interrupt to the process. On Unix this is a
     #' `SIGINT` signal, and it is usually equivalent to pressing CTRL+C at
     #' the terminal prompt. On Windows, it is a CTRL+BREAK keypress.
     #' Applications may catch these events. By default they will quit.
+    #' @param group Whether to send the interrupt to the whole process group
+    #'   of the child. See `$signal()` for details. Ignored on Windows,
+    #'   where the CTRL+BREAK event is always delivered to all processes
+    #'   attached to the child's console.
 
-    interrupt = function() process_interrupt(self, private),
+    interrupt = function(group = TRUE) process_interrupt(self, private, group),
 
     #' @description
     #' Query the process id.
@@ -846,24 +858,30 @@ process_get_exit_status <- function(self, private) {
   )
 }
 
-process_signal <- function(self, private, signal) {
+process_signal <- function(self, private, signal, group) {
   "!DEBUG process_signal `private$get_short_name()` `signal`"
   chain_call(
     c_processx_signal,
     private$status,
     as.integer(signal),
-    private$get_short_name()
+    private$get_short_name(),
+    as.logical(group)
   )
 }
 
-process_interrupt <- function(self, private) {
+process_interrupt <- function(self, private, group) {
   "!DEBUG process_interrupt `private$get_short_name()`"
   if (os_type() == "windows") {
     pid <- as.character(self$get_pid())
     st <- run(get_tool("interrupt"), c(pid, "c"), error_on_status = FALSE)
     if (st$status == 0) TRUE else FALSE
   } else {
-    chain_call(c_processx_interrupt, private$status, private$get_short_name())
+    chain_call(
+      c_processx_interrupt,
+      private$status,
+      private$get_short_name(),
+      as.logical(group)
+    )
   }
 }
 

src/init.c

@@ -103,8 +103,8 @@ static const R_CallMethodDef callMethods[]  = {
   { "processx_is_alive",           (DL_FUNC) &processx_is_alive,           2 },
   { "processx_pty_close",          (DL_FUNC) &processx_pty_close,          2 },
   { "processx_get_exit_status",    (DL_FUNC) &processx_get_exit_status,    2 },
-  { "processx_signal",             (DL_FUNC) &processx_signal,             3 },
-  { "processx_interrupt",          (DL_FUNC) &processx_interrupt,          2 },
+  { "processx_signal",             (DL_FUNC) &processx_signal,             4 },
+  { "processx_interrupt",          (DL_FUNC) &processx_interrupt,          3 },
   { "processx_kill",               (DL_FUNC) &processx_kill,               3 },
   { "processx_get_pid",            (DL_FUNC) &processx_get_pid,            1 },
   { "processx_create_time",        (DL_FUNC) &processx_create_time,        1 },

src/processx.h

@@ -51,8 +51,8 @@ SEXP processx_wait(SEXP status, SEXP timeout, SEXP name);
 SEXP processx_is_alive(SEXP status, SEXP name);
 SEXP processx_pty_close(SEXP status, SEXP name);
 SEXP processx_get_exit_status(SEXP status, SEXP name);
-SEXP processx_signal(SEXP status, SEXP signal, SEXP name);
-SEXP processx_interrupt(SEXP status, SEXP name);
+SEXP processx_signal(SEXP status, SEXP signal, SEXP name, SEXP group);
+SEXP processx_interrupt(SEXP status, SEXP name, SEXP group);
 SEXP processx_kill(SEXP status, SEXP grace, SEXP name);
 SEXP processx_get_pid(SEXP status);
 SEXP processx_create_time(SEXP r_pid);

src/unix/processx.c

@@ -964,11 +964,12 @@ SEXP processx_get_exit_status(SEXP status, SEXP name) {
  * the SIGCHLD handler.
  */
 
-SEXP processx_signal(SEXP status, SEXP signal, SEXP name) {
+SEXP processx_signal(SEXP status, SEXP signal, SEXP name, SEXP group) {
   processx_handle_t *handle = R_ExternalPtrAddr(status);
   const char *cname = isNull(name) ? "???" : CHAR(STRING_ELT(name, 0));
   pid_t pid;
   int wstat, wp, ret, result;
+  int cgroup = LOGICAL(group)[0];
 
   processx__block_sigchld();
 
@@ -983,13 +984,17 @@ SEXP processx_signal(SEXP status, SEXP signal, SEXP name) {
     goto cleanup;
   }
 
-  /* Otherwise try to send signal */
+  /* Otherwise try to send signal. The child is started in its own
+     process group (via setsid()), so its pgid equals its pid; negating
+     the pid sends the signal to the whole group. ESRCH/EPERM mean the
+     original target is gone (the PID/PGID may have been reused, possibly
+     by a process we may not signal). */
   pid = handle->pid;
-  ret = kill(pid, INTEGER(signal)[0]);
+  ret = kill(cgroup ? -pid : pid, INTEGER(signal)[0]);
 
   if (ret == 0) {
     result = 1;
-  } else if (ret == -1 && errno == ESRCH) {
+  } else if (ret == -1 && (errno == ESRCH || errno == EPERM)) {
     result = 0;
   } else {
     processx__unblock_sigchld();
@@ -1018,8 +1023,8 @@ SEXP processx_signal(SEXP status, SEXP signal, SEXP name) {
   return ScalarLogical(result);
 }
 
-SEXP processx_interrupt(SEXP status, SEXP name) {
-  return processx_signal(status, ScalarInteger(2), name);
+SEXP processx_interrupt(SEXP status, SEXP name, SEXP group) {
+  return processx_signal(status, ScalarInteger(2), name, group);
 }
 
 /* This is a special case of `processx_signal`, and we implement it almost

src/win/processx.c

@@ -1540,10 +1540,11 @@ SEXP processx_get_exit_status(SEXP status, SEXP name) {
   }
 }
 
-SEXP processx_signal(SEXP status, SEXP signal, SEXP name) {
+SEXP processx_signal(SEXP status, SEXP signal, SEXP name, SEXP group) {
   processx_handle_t *handle = R_ExternalPtrAddr(status);
   const char *cname = isNull(name) ? "???" : CHAR(STRING_ELT(name, 0));
   DWORD err, exitcode = STILL_ACTIVE;
+  (void) group;
 
   if (!handle) return ScalarLogical(0);
   if (handle->collected) return ScalarLogical(0);
@@ -1591,13 +1592,14 @@ SEXP processx_signal(SEXP status, SEXP signal, SEXP name) {
   }
 }
 
-SEXP processx_interrupt(SEXP status, SEXP name) {
+SEXP processx_interrupt(SEXP status, SEXP name, SEXP group) {
+  (void) group;
   R_THROW_ERROR("Internal processx error, `processx_interrupt()` should not be called");
   return R_NilValue;
 }
 
 SEXP processx_kill(SEXP status, SEXP grace, SEXP name) {
-  return processx_signal(status, ScalarInteger(9), name);
+  return processx_signal(status, ScalarInteger(9), name, ScalarLogical(1));
 }
 
 SEXP processx_get_pid(SEXP status) {