update

ts/smartmetrics.pidtree.ts

@@ -0,0 +1,55 @@
+import * as fs from 'fs';
+
+// Get all descendant PIDs of the given root PID by reading /proc/<pid>/stat.
+// Returns an array of descendant PIDs (excludes the root itself).
+export async function getChildPids(rootPid: number): Promise<number[]> {
+  const parentMap = new Map<number, number[]>(); // parent → children
+
+  let entries: string[];
+  try {
+    entries = fs.readdirSync('/proc');
+  } catch {
+    return [];
+  }
+
+  for (const entry of entries) {
+    const pid = parseInt(entry, 10);
+    if (isNaN(pid)) continue;
+
+    try {
+      const stat = fs.readFileSync(`/proc/${pid}/stat`, 'utf8');
+      // Format: pid (comm) state ppid ...
+      // comm can contain spaces and parentheses, so find the last ')' first
+      const closeParenIdx = stat.lastIndexOf(')');
+      if (closeParenIdx === -1) continue;
+      const afterComm = stat.slice(closeParenIdx + 2); // skip ') '
+      const fields = afterComm.split(' ');
+      const ppid = parseInt(fields[1], 10); // field index 1 after state is ppid
+
+      if (!parentMap.has(ppid)) {
+        parentMap.set(ppid, []);
+      }
+      parentMap.get(ppid)!.push(pid);
+    } catch {
+      // Process may have exited between readdir and readFile
+      continue;
+    }
+  }
+
+  // BFS from rootPid to collect all descendants
+  const result: number[] = [];
+  const queue: number[] = [rootPid];
+
+  while (queue.length > 0) {
+    const current = queue.shift()!;
+    const children = parentMap.get(current);
+    if (children) {
+      for (const child of children) {
+        result.push(child);
+        queue.push(child);
+      }
+    }
+  }
+
+  return result;
+}