Implement programmatic notifications

Add support for running a script for each process killed (or would kill
in dryrun mode).

Signed-off-by: Nikos Tsipinakis <nikos.tsipinakis@cern.ch>

MANPAGE.md

@@ -108,6 +108,19 @@ To actually see the notifications in your GUI session, you need to have
 [systembus-notify](https://github.com/rfjakob/systembus-notify)
 running as your user.
 
+#### -N SCRIPT
+Run the given script for each process killed.
+
+Within the script, information about the killed process can be obtained via the
+following environment variables:
+
+    EARLYOOM_PID     Process PID
+    EARLYOOM_NAME    Process name/path
+    EARLYOOM_UID     UID of the user running the process
+
+Warning: In case of dryrun mode, the script will be executed in rapid
+succession, ensure you have some sort of rate-limit implemented.
+
 #### -g
 Kill all processes that have same process group id (PGID) as the process
 with excessive memory usage.

README.md

@@ -195,6 +195,13 @@ To actually see the notifications in your GUI session, you need to have
 [systembus-notify](https://github.com/rfjakob/systembus-notify)
 running as your user.
 
+Additionally, earlyoom can execute a script for each process killed, providing
+information about the process via the `EARLYOOM_PID`, `EARLYOOM_UID` and
+`EARLYOOM_NAME` environment variables. Pass `-N /path/to/script` to enable.
+
+Warning: In case of dryrun mode, the script will be executed in rapid
+succession, ensure you have some sort of rate-limit implemented.
+
 ### Preferred Processes
 
 The command-line flag `--prefer` specifies processes to prefer killing;

kill.c

@@ -21,6 +21,9 @@
 #define BADNESS_PREFER 300
 #define BADNESS_AVOID -300
 
+// Buffer size for UID/GID/PID string conversion
+#define UID_BUFSIZ 128
+
 static int isnumeric(char* str)
 {
     int i = 0;
@@ -61,6 +64,32 @@ static void notify(const char* summary, const char* body)
     exit(1);
 }
 
+static void notify_ext(const char* script, const procinfo_t victim)
+{
+    pid_t pid1 = fork();
+
+    if (pid1 == -1) {
+        warn("fork() returned -1: %s\n", strerror(errno));
+        return;
+    } else if (pid1 != 0) {
+        return;
+    }
+
+    char pid_str[UID_BUFSIZ];
+    char uid_str[UID_BUFSIZ];
+
+    snprintf(pid_str, UID_BUFSIZ, "%d", victim.pid);
+    snprintf(uid_str, UID_BUFSIZ, "%d", victim.uid);
+
+    setenv("EARLYOOM_PID", pid_str, 1);
+    setenv("EARLYOOM_UID", uid_str, 1);
+    setenv("EARLYOOM_NAME", victim.name, 1);
+
+    execlp(script, script, NULL);
+    warn("notify_ext: exec failed: %s\n", strerror(errno));
+    exit(1);
+}
+
 /*
  * Send the selected signal to "pid" and wait for the process to exit
  * (max 10 seconds)
@@ -312,6 +341,9 @@ void kill_process(const poll_loop_args_t* args, int sig, const procinfo_t victim
         if (args->notify) {
             notify("earlyoom", notif_args);
         }
+        if (args->notify_ext) {
+            notify_ext(args->notify_ext, victim);
+        }
     }
 
     if (sig == 0) {

kill.h

@@ -16,6 +16,8 @@ typedef struct {
     double swap_kill_percent;
     /* send d-bus notifications? */
     bool notify;
+    /* Path to script for programmatic notifications (or NULL) */
+    char *notify_ext;
     /* kill all processes within a process group */
     bool kill_process_group;
     /* prefer/avoid killing these processes. NULL = no-op. */

main.c

@@ -176,8 +176,7 @@ int main(int argc, char* argv[])
             args.kill_process_group = true;
             break;
         case 'N':
-            args.notify = true;
-            fprintf(stderr, "Notifying through D-Bus, argument '%s' ignored for compatability\n", optarg);
+            args.notify_ext = optarg;
             break;
         case 'd':
             enable_debug = 1;
@@ -220,6 +219,7 @@ int main(int argc, char* argv[])
                 "  -M SIZE[,KILL_SIZE]       set available memory minimum to SIZE KiB\n"
                 "  -S SIZE[,KILL_SIZE]       set free swap minimum to SIZE KiB\n"
                 "  -n                        enable d-bus notifications\n"
+                "  -N                        enable programmatic notifications\n"
                 "  -g                        kill all processes within a process group\n"
                 "  -d                        enable debugging messages\n"
                 "  -v                        print version information and exit\n"