I have also asked about this question in Russian Cocoa Developers Slack channel and received the answer from Dmitry Rodionov. He answered in Russian with this gist: ctrlc-ptty-nstask.markdown and gave me approval to post English version of it here.
His implementation is based on what Pokey McPokerson suggested but is more straightforward: he uses GetBSDProcessList() from Technical Q&A QA1123
Getting List of All Processes on Mac OS X to get the list of the child processes and to send SIGINT to each of them:
kinfo_proc *procs = NULL;
size_t count;
if (0 != GetBSDProcessList(&procs, &count)) {
return;
}
BOOL hasChildren = NO;
for (size_t i = 0; i < count; i++) {
// If the process if a child of our bash process we send SIGINT to it
if (procs[i].kp_eproc.e_ppid == task.processIdentifier) {
hasChildren = YES;
kill(procs[i].kp_proc.p_pid, SIGINT);
}
}
free(procs);
In case if a process has no child processes he sends SIGINT to that process directly:
if (hasChildren == NO) {
kill(task.processIdentifier, SIGINT);
}
This approach works perfectly however there are two possible concerns (which I personally don't care about at the moment I'm writing my own toy terminal):
- It is exhaustive to enumerate through all the processes every time Ctrl-C is pressed. Maybe there is a better way of finding child processes.
- I and Dmitriy we are both not sure if killing ALL child processes is the way how Ctrl-C works in real terminals.
Below the full version of Dmitriy's code follows:
- (void)keyDown:(NSEvent *)theEvent
{
NSUInteger flags = theEvent.modifierFlags;
unsigned short keyCode = theEvent.keyCode;
if ((flags & NSControlKeyMask) && keyCode == 8) {
[self sendCtrlC];
} else if ((flags & NSControlKeyMask) && keyCode == 2) {
[masterHandle writeData:[NSData dataWithBytes: "\004" length:1]];
} else if ((flags & NSDeviceIndependentModifierFlagsMask) == 0 && keyCode == 126) {
NSLog(@"up");
} else if ((flags & NSDeviceIndependentModifierFlagsMask) == 0 && keyCode == 125) {
NSLog(@"down");
} else {
[super keyDown:theEvent];
}
}
// #include <sys/sysctl.h>
// typedef struct kinfo_proc kinfo_proc;
- (void)sendCtrlC
{
[masterHandle writeData:[NSData dataWithBytes: "\003" length:1]];
kinfo_proc *procs = NULL;
size_t count;
if (0 != GetBSDProcessList(&procs, &count)) {
return;
}
BOOL hasChildren = NO;
for (size_t i = 0; i < count; i++) {
if (procs[i].kp_eproc.e_ppid == task.processIdentifier) {
hasChildren = YES;
kill(procs[i].kp_proc.p_pid, SIGINT);
}
}
free(procs);
if (hasChildren == NO) {
kill(task.processIdentifier, SIGINT);
}
}
static int GetBSDProcessList(kinfo_proc **procList, size_t *procCount)
// Returns a list of all BSD processes on the system. This routine
// allocates the list and puts it in *procList and a count of the
// number of entries in *procCount. You are responsible for freeing
// this list (use "free" from System framework).
// On success, the function returns 0.
// On error, the function returns a BSD errno value.
{
int err;
kinfo_proc * result;
bool done;
static const int name[] = { CTL_KERN, KERN_PROC, KERN_PROC_ALL, 0 };
// Declaring name as const requires us to cast it when passing it to
// sysctl because the prototype doesn't include the const modifier.
size_t length;
assert( procList != NULL);
assert(*procList == NULL);
assert(procCount != NULL);
*procCount = 0;
// We start by calling sysctl with result == NULL and length == 0.
// That will succeed, and set length to the appropriate length.
// We then allocate a buffer of that size and call sysctl again
// with that buffer. If that succeeds, we're done. If that fails
// with ENOMEM, we have to throw away our buffer and loop. Note
// that the loop causes use to call sysctl with NULL again; this
// is necessary because the ENOMEM failure case sets length to
// the amount of data returned, not the amount of data that
// could have been returned.
result = NULL;
done = false;
do {
assert(result == NULL);
// Call sysctl with a NULL buffer.
length = 0;
err = sysctl( (int *) name, (sizeof(name) / sizeof(*name)) - 1,
NULL, &length,
NULL, 0);
if (err == -1) {
err = errno;
}
// Allocate an appropriately sized buffer based on the results
// from the previous call.
if (err == 0) {
result = malloc(length);
if (result == NULL) {
err = ENOMEM;
}
}
// Call sysctl again with the new buffer. If we get an ENOMEM
// error, toss away our buffer and start again.
if (err == 0) {
err = sysctl( (int *) name, (sizeof(name) / sizeof(*name)) - 1,
result, &length,
NULL, 0);
if (err == -1) {
err = errno;
}
if (err == 0) {
done = true;
} else if (err == ENOMEM) {
assert(result != NULL);
free(result);
result = NULL;
err = 0;
}
}
} while (err == 0 && ! done);
// Clean up and establish post conditions.
if (err != 0 && result != NULL) {
free(result);
result = NULL;
}
*procList = result;
if (err == 0) {
*procCount = length / sizeof(kinfo_proc);
}
assert( (err == 0) == (*procList != NULL) );
return err;
}
