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

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+const exec = require('child_process').exec;
+const tree = require('./tree');
+const utils = require('./utils');
+var hasPS = true;
+
+// discover if the OS has `ps`, and therefore can use psTree
+exec('ps', (error) => {
+  module.exports.hasPS = hasPS = !error;
+});
+
+module.exports = function main(pid, callback) {
+  if (typeof pid === 'number') {
+    pid = pid.toString();
+  }
+
+  if (hasPS && !process.env.NO_PS) {
+    return tree(pid, callback);
+  }
+
+  utils
+    .getStat()
+    .then(utils.tree)
+    .then((tree) => utils.pidsForTree(tree, pid))
+    .then((res) =>
+      callback(
+        null,
+        res.map((p) => p.PID)
+      )
+    )
+    .catch((error) => callback(error));
+};
+
+if (!module.parent) {
+  module.exports(process.argv[2], (e, pids) => console.log(pids));
+}
+
+module.exports.hasPS = hasPS;

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);
+    }
+  });
+};

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

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+const spawn = require('child_process').spawn;
+
+module.exports = { tree, pidsForTree, getStat };
+
+function getStat() {
+  return new Promise((resolve) => {
+    const command = `ls /proc | grep -E '^[0-9]+$' | xargs -I{} cat /proc/{}/stat`;
+    const spawned = spawn('sh', ['-c', command], {
+      stdio: ['pipe', 'pipe', 'pipe'],
+    });
+
+    var res = '';
+    spawned.stdout.on('data', (data) => (res += data));
+    spawned.on('close', () => resolve(res));
+  });
+}
+
+function template(s) {
+  var stat = null;
+  // 'pid', 'comm', 'state', 'ppid', 'pgrp'
+  // %d     (%s)    %c       %d      %d
+  s.replace(
+    /(\d+) \((.*?)\)\s(.+?)\s(\d+)\s/g,
+    (all, PID, COMMAND, STAT, PPID) => {
+      stat = { PID, COMMAND, PPID, STAT };
+    }
+  );
+
+  return stat;
+}
+
+function tree(stats) {
+  const processes = stats.split('\n').map(template).filter(Boolean);
+
+  return processes;
+}
+
+function pidsForTree(tree, pid) {
+  if (typeof pid === 'number') {
+    pid = pid.toString();
+  }
+  const parents = [pid];
+  const pids = [];
+
+  tree.forEach((proc) => {
+    if (parents.indexOf(proc.PPID) !== -1) {
+      parents.push(proc.PID);
+      pids.push(proc);
+    }
+  });
+
+  return pids;
+}