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Assignment-3/node_modules/pstree.remy/lib/tree.js

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+const spawn = require('child_process').spawn;
+
+module.exports = function (rootPid, callback) {
+  const pidsOfInterest = new Set([parseInt(rootPid, 10)]);
+  var output = '';
+
+  // *nix
+  const ps = spawn('ps', ['-A', '-o', 'ppid,pid']);
+  ps.stdout.on('data', (data) => {
+    output += data.toString('ascii');
+  });
+
+  ps.on('close', () => {
+    try {
+      const res = output
+        .split('\n')
+        .slice(1)
+        .map((_) => _.trim())
+        .reduce((acc, line) => {
+          const pids = line.split(/\s+/);
+          const ppid = parseInt(pids[0], 10);
+
+          if (pidsOfInterest.has(ppid)) {
+            const pid = parseInt(pids[1], 10);
+            acc.push(pid);
+            pidsOfInterest.add(pid);
+          }
+
+          return acc;
+        }, []);
+
+      callback(null, res);
+    } catch (e) {
+      callback(e, null);
+    }
+  });
+};