ref: d3e49bb897e483fbde5bf3f7ac2b527fc71bde17
dir: /sys/src/libc/9sys/postnote.c/
#include <u.h>
#include <libc.h>
int
postnote(int group, int pid, char *note)
{
	char file[32];
	int f, r;
	switch(group) {
	case PNPROC:
		snprint(file, sizeof(file), "/proc/%lud/note", (ulong)pid);
		break;
	case PNGROUP:
		snprint(file, sizeof(file), "/proc/%lud/notepg", (ulong)pid);
		break;
	default:
		return -1;
	}
	f = open(file, OWRITE|OCEXEC);
	if(f < 0)
		return -1;
	r = strlen(note);
	if(write(f, note, r) != r) {
		close(f);
		return -1;
	}
	close(f);
	return 0;
}