Add timeout and maxBuffer options to child_process.exec

doc/api.markdown

@@ -907,7 +907,7 @@ Example:
     grep.stdin.end();
 
 
-### child_process.exec(command, callback)
+### child_process.exec(command, [options, ] callback)
 
 High-level way to execute a command as a child process, buffer the
 output, and return it all in a callback.
@@ -928,6 +928,20 @@ The callback gets the arguments `(error, stdout, stderr)`. On success, `error`
 will be `null`.  On error, `error` will be an instance of `Error` and `err.code`
 will be the exit code of the child process.
 
+There is a second optional argument to specify several options. The default options are
+
+    { encoding: 'utf8'
+    , timeout: 0
+    , maxBuffer: 200*1024
+    , killSignal: 'SIGKILL'
+    }
+
+If `timeout` is greater than 0, then it will kill the child process
+if it runs longer than `timeout` milliseconds. The child process is killed with
+`killSignal` (default: `'SIGKILL'`). `maxBuffer` specifies the largest
+amount of data allowed on stdout or stderr - if this value is exceeded then
+the child process is killed.
+
 
 
 ## File System

lib/child_process.js

@@ -11,22 +11,64 @@ var spawn = exports.spawn = function (path, args, env) {
 };
 
 
-exports.exec = function (command, callback) {
+exports.exec = function (command /* , options, callback */) {
+  var options = { encoding: 'utf8'
+                , timeout: 0
+                , maxBuffer: 200*1024
+                , killSignal: 'SIGKILL'
+                };
+
+  var callback = arguments[arguments.length-1];
+  if (typeof arguments[1] == 'object') {
+    var keys = Object.keys(options);
+    for (var i = 0; i < keys.length; i++) {
+      var k = keys[i];
+      if (arguments[1][k] !== undefined) options[k] = arguments[1][k];
+    }
+  }
+
   var child = spawn("/bin/sh", ["-c", command]);
   var stdout = "";
   var stderr = "";
+  var killed = false;
+
+  var timeoutId;
+  if (options.timeout > 0) {
+    timeoutId = setTimeout(function () {
+      if (!killed) {
+        child.kill(options.killSignal);
+        killed = true;
+        timeoutId = null;
+      }
+    }, options.timeout);
+  }
+
+  child.stdout.setEncoding(options.encoding);
+  child.stderr.setEncoding(options.encoding);
 
-  child.stdout.setEncoding('utf8');
-  child.stdout.addListener("data", function (chunk) { stdout += chunk; });
+  child.stdout.addListener("data", function (chunk) {
+    stdout += chunk;
+    if (!killed && stdout.length > options.maxBuffer) {
+      child.kill(options.killSignal);
+      killed = true;
+    }
+  });
 
-  child.stderr.setEncoding('utf8');
-  child.stderr.addListener("data", function (chunk) { stderr += chunk; });
+  child.stderr.addListener("data", function (chunk) {
+    stderr += chunk;
+    if (!killed && stderr.length > options.maxBuffer) {
+      child.kill(options.killSignal);
+      killed = true
+    }
+  });
 
   child.addListener("exit", function (code) {
+    if (timeoutId) clearTimeout(timeoutId);
     if (code == 0) {
       if (callback) callback(null, stdout, stderr);
     } else {
       var e = new Error("Command failed: " + stderr);
+      e.killed = killed;
       e.code = code;
       if (callback) callback(e, stdout, stderr);
     }

test/simple/test-exec.js

@@ -9,6 +9,7 @@ exec("ls /", function (err, stdout, stderr) {
     puts("error!: " + err.code);
     puts("stdout: " + JSON.stringify(stdout));
     puts("stderr: " + JSON.stringify(stderr));
+    assert.equal(false, err.killed);
   } else {
     success_count++;
     p(stdout);
@@ -21,6 +22,7 @@ exec("ls /DOES_NOT_EXIST", function (err, stdout, stderr) {
     error_count++;
     assert.equal("", stdout);
     assert.equal(true, err.code != 0);
+    assert.equal(false, err.killed);
     puts("error code: " + err.code);
     puts("stdout: " + JSON.stringify(stdout));
     puts("stderr: " + JSON.stringify(stderr));
@@ -31,6 +33,15 @@ exec("ls /DOES_NOT_EXIST", function (err, stdout, stderr) {
   }
 });
 
+exec("sleep 10", { timeout: 50 }, function (err, stdout, stderr) {
+  assert.ok(err);
+  assert.ok(err.killed);
+});
+
+exec('python -c "print 200000*\'C\'"', { maxBuffer: 1000 }, function (err, stdout, stderr) {
+  assert.ok(err);
+  assert.ok(err.killed);
+});
 
 process.addListener("exit", function () {
   assert.equal(1, success_count);