[monitoring-plugins] check_users: Discard sessions with invalid or ...

[GitHub]

    Module: monitoring-plugins
    Branch: master
    Commit: c7430767d83a4429ffeb55f1f1b13ba5ee3477cd
    Author: Hilko Bengen <bengen--github at hilluzination.de>
 Committer: GitHub <noreply at github.com>
      Date: Sun Sep  6 23:35:55 2026 +0200
       URL: https://www.monitoring-plugins.org/repositories/monitoring-plugins/commit/?id=c7430767

check_users: Discard sessions with invalid or missing pid in utmp (#2336)

The `signal(pid, 0)` check matches what who(1) from coreutils does.

(I have checked versions 9.4 and 9.7.)

---

 plugins/check_users.d/users.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/plugins/check_users.d/users.c b/plugins/check_users.d/users.c
index ec7e0bac..289d0ed5 100644
--- a/plugins/check_users.d/users.c
+++ b/plugins/check_users.d/users.c
@@ -83,6 +83,8 @@ get_num_of_users_wrapper get_num_of_users_systemd() {
 
 #	ifdef HAVE_UTMPX_H
 #		include <utmpx.h>
+#		include <errno.h>
+#		include <signal.h>
 
 get_num_of_users_wrapper get_num_of_users_utmp() {
 	int users = 0;
@@ -92,9 +94,13 @@ get_num_of_users_wrapper get_num_of_users_utmp() {
 
 	struct utmpx *putmpx;
 	while ((putmpx = getutxent()) != NULL) {
-		if (putmpx->ut_type == USER_PROCESS) {
-			users++;
+		if (putmpx->ut_type != USER_PROCESS) {
+			continue;
+		}
+		if ((putmpx->ut_pid <= 0) || ((kill(putmpx->ut_pid, 0) != 0) && (errno == ESRCH))) {
+			continue;
 		}
+		users++;
 	}
 
 	endutxent();