2 * cgroup_event_listener.c - Simple listener of cgroup events
4 * Copyright (C) Kirill A. Shutemov <kirill@shutemov.name>
16 #include <sys/eventfd.h>
18 #define USAGE_STR "Usage: cgroup_event_listener <path-to-control-file> <args>\n"
20 int main(int argc, char **argv)
24 int event_control = -1;
25 char event_control_path[PATH_MAX];
30 fputs(USAGE_STR, stderr);
34 cfd = open(argv[1], O_RDONLY);
36 fprintf(stderr, "Cannot open %s: %s\n", argv[1],
41 ret = snprintf(event_control_path, PATH_MAX, "%s/cgroup.event_control",
43 if (ret >= PATH_MAX) {
44 fputs("Path to cgroup.event_control is too long\n", stderr);
48 event_control = open(event_control_path, O_WRONLY);
49 if (event_control == -1) {
50 fprintf(stderr, "Cannot open %s: %s\n", event_control_path,
57 perror("eventfd() failed");
61 ret = snprintf(line, LINE_MAX, "%d %d %s", efd, cfd, argv[2]);
62 if (ret >= LINE_MAX) {
63 fputs("Arguments string is too long\n", stderr);
67 ret = write(event_control, line, strlen(line) + 1);
69 perror("Cannot write to cgroup.event_control");
76 ret = read(efd, &result, sizeof(result));
80 perror("Cannot read from eventfd");
83 assert(ret == sizeof(result));
85 ret = access(event_control_path, W_OK);
86 if ((ret == -1) && (errno == ENOENT)) {
87 puts("The cgroup seems to have removed.");
93 perror("cgroup.event_control "
94 "is not accessible any more");
98 printf("%s %s: crossed\n", argv[1], argv[2]);
104 if (event_control >= 0)
105 close(event_control);