Use the command builtin rather than which.

lib/src/global_packages.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
 import 'package:barback/barback.dart';
 import 'package:pub_semver/pub_semver.dart';
@@ skipping 752 matching lines @@
       if (result.exitCode == 0) return;
 
       log.warning(
           "${log.yellow('Warning:')} Pub installs executables into "
               "${log.bold(_binStubDir)}, which is not on your path.\n"
           "You can fix that by adding that directory to your system's "
               '"Path" environment variable.\n'
           'A web search for "configure windows path" will show you how.');
     } else {
       // See if the shell can find one of the binstubs.
-      var result = runProcessSync("which", [installed]);
+      //
+      // The "command" builtin is more reliable than the "which" executable. See
+      // http://unix.stackexchange.com/questions/85249/why-not-use-which-what-to-use-then
+      var result = runProcessSync("sh", ["-c", 'command -v "\$installed"'],

[kevmoo, 2016/07/14 21:22:13]

...or just add 'runInShell: true' ?

[nweiz, 2016/07/14 22:06:56]

Haha good idea!

+          environment: {"installed": installed});
       if (result.exitCode == 0) return;
 
       var binDir = _binStubDir;
       if (binDir.startsWith(Platform.environment['HOME'])) {
         binDir = p.join("~", p.relative(binDir,
             from: Platform.environment['HOME']));
       }
 
       log.warning(
           "${log.yellow('Warning:')} Pub installs executables into "
               "${log.bold(binDir)}, which is not on your path.\n"
           "You can fix that by adding this to your shell's config file "
               "(.bashrc, .bash_profile, etc.):\n"
           "\n"
           "  ${log.bold('export PATH="\$PATH":"$binDir"')}\n"
           "\n");
     }
   }
 
   /// Returns the value of the property named [name] in the bin stub script
   /// [source].
   String _binStubProperty(String source, String name) {
     var pattern = new RegExp(quoteRegExp(name) + r": ([a-zA-Z0-9_-]+)");
     var match = pattern.firstMatch(source);
     return match == null ? null : match[1];
   }
 }