//
// ShellJS
// Unix shell commands on top of Node's API
//
// Copyright (c) 2012 Artur Adib
// http://github.com/arturadib/shelljs
//

var fs = require('fs'),
    path = require('path'),
    util = require('util'),
    vm = require('vm'),
    child = require('child_process'),
    os = require('os');

// Node shims for < v0.7
fs.existsSync = fs.existsSync || path.existsSync;

var config = {
  silent: false,
  fatal: false
};

var state = {
      error: null,
      currentCmd: 'shell.js',
      tempDir: null
    },
    platform = os.type().match(/^Win/) ? 'win' : 'unix';


//@
//@ All commands run synchronously, unless otherwise stated.
//@


//@
//@ ### cd('dir')
//@ Changes to directory `dir` for the duration of the script
function _cd(options, dir) {
  if (!dir)
    error('directory not specified');

  if (!fs.existsSync(dir))
    error('no such file or directory: ' + dir);

  if (!fs.statSync(dir).isDirectory())
    error('not a directory: ' + dir);

  process.chdir(dir);
}
exports.cd = wrap('cd', _cd);

//@
//@ ### pwd()
//@ Returns the current directory.
function _pwd(options) {
  var pwd = path.resolve(process.cwd());
  return ShellString(pwd);
}
exports.pwd = wrap('pwd', _pwd);


//@
//@ ### ls([options ,] path [,path ...])
//@ ### ls([options ,] path_array)
//@ Available options:
//@
//@ + `-R`: recursive
//@ + `-A`: all files (include files beginning with `.`, except for `.` and `..`)
//@
//@ Examples:
//@
//@ ```javascript
//@ ls('projs/*.js');
//@ ls('-R', '/users/me', '/tmp');
//@ ls('-R', ['/users/me', '/tmp']); // same as above
//@ ```
//@
//@ Returns array of files in the given path, or in current directory if no path provided.
function _ls(options, paths) {
  options = parseOptions(options, {
    'R': 'recursive',
    'A': 'all',
    'a': 'all_deprecated'
  });

  if (options.all_deprecated) {
    // We won't support the -a option as it's hard to image why it's useful
    // (it includes '.' and '..' in addition to '.*' files)
    // For backwards compatibility we'll dump a deprecated message and proceed as before
    log('ls: Option -a is deprecated. Use -A instead');
    options.all = true;
  }

  if (!paths)
    paths = ['.'];
  else if (typeof paths === 'object')
    paths = paths; // assume array
  else if (typeof paths === 'string')
    paths = [].slice.call(arguments, 1);

  var list = [];

  // Conditionally pushes file to list - returns true if pushed, false otherwise
  // (e.g. prevents hidden files to be included unless explicitly told so)
  function pushFile(file, query) {
    // hidden file?
    if (path.basename(file)[0] === '.') {
      // not explicitly asking for hidden files?
      if (!options.all && !(path.basename(query)[0] === '.' && path.basename(query).length > 1))
        return false;
    }

    if (platform === 'win')
      file = file.replace(/\\/g, '/');

    list.push(file);
    return true;
  }

  paths.forEach(function(p) {
    if (fs.existsSync(p)) {
      var stats = fs.statSync(p);
      // Simple file?
      if (stats.isFile()) {
        pushFile(p, p);
        return; // continue
      }

      // Simple dir?
      if (stats.isDirectory()) {
        // Iterate over p contents
        fs.readdirSync(p).forEach(function(file) {
          if (!pushFile(file, p))
            return;

          // Recursive?
          if (options.recursive) {
            var oldDir = _pwd();
            _cd('', p);
            if (fs.statSync(file).isDirectory())
              list = list.concat(_ls('-R'+(options.all?'A':''), file+'/*'));
            _cd('', oldDir);
          }
        });
        return; // continue
      }
    }

    // p does not exist - possible wildcard present

    var basename = path.basename(p);
    var dirname = path.dirname(p);
    // Wildcard present on an existing dir? (e.g. '/tmp/*.js')
    if (basename.search(/\*/) > -1 && fs.existsSync(dirname) && fs.statSync(dirname).isDirectory) {
      // Escape special regular expression chars
      var regexp = basename.replace(/(\^|\$|\(|\)|<|>|\[|\]|\{|\}|\.|\+|\?)/g, '\\$1');
      // Translates wildcard into regex
      regexp = '^' + regexp.replace(/\*/g, '.*') + '$';
      // Iterate over directory contents
      fs.readdirSync(dirname).forEach(function(file) {
        if (file.match(new RegExp(regexp))) {
          if (!pushFile(path.normalize(dirname+'/'+file), basename))
            return;

          // Recursive?
          if (options.recursive) {
            var pp = dirname + '/' + file;
            if (fs.lstatSync(pp).isDirectory())
              list = list.concat(_ls('-R'+(options.all?'A':''), pp+'/*'));
          } // recursive
        } // if file matches
      }); // forEach
      return;
    }

    error('no such file or directory: ' + p, true);
  });

  return list;
}
exports.ls = wrap('ls', _ls);


//@
//@ ### find(path [,path ...])
//@ ### find(path_array)
//@ Examples:
//@
//@ ```javascript
//@ find('src', 'lib');
//@ find(['src', 'lib']); // same as above
//@ find('.').filter(function(file) { return file.match(/\.js$/); });
//@ ```
//@
//@ Returns array of all files (however deep) in the given paths.
//@
//@ The main difference from `ls('-R', path)` is that the resulting file names
//@ include the base directories, e.g. `lib/resources/file1` instead of just `file1`.
function _find(options, paths) {
  if (!paths)
    error('no path specified');
  else if (typeof paths === 'object')
    paths = paths; // assume array
  else if (typeof paths === 'string')
    paths = [].slice.call(arguments, 1);

  var list = [];

  function pushFile(file) {
    if (platform === 'win')
      file = file.replace(/\\/g, '/');
    list.push(file);
  }

  // why not simply do ls('-R', paths)? because the output wouldn't give the base dirs
  // to get the base dir in the output, we need instead ls('-R', 'dir/*') for every directory

  paths.forEach(function(file) {
    pushFile(file);

    if (fs.statSync(file).isDirectory()) {
      _ls('-RA', file+'/*').forEach(function(subfile) {
        pushFile(subfile);
      });
    }
  });

  return list;
}
exports.find = wrap('find', _find);


//@
//@ ### cp([options ,] source [,source ...], dest)
//@ ### cp([options ,] source_array, dest)
//@ Available options:
//@
//@ + `-f`: force
//@ + `-r, -R`: recursive
//@
//@ Examples:
//@
//@ ```javascript
//@ cp('file1', 'dir1');
//@ cp('-Rf', '/tmp/*', '/usr/local/*', '/home/tmp');
//@ cp('-Rf', ['/tmp/*', '/usr/local/*'], '/home/tmp'); // same as above
//@ ```
//@
//@ Copies files. The wildcard `*` is accepted.
function _cp(options, sources, dest) {
  options = parseOptions(options, {
    'f': 'force',
    'R': 'recursive',
    'r': 'recursive'
  });

  // Get sources, dest
  if (arguments.length < 3) {
    error('missing <source> and/or <dest>');
  } else if (arguments.length > 3) {
    sources = [].slice.call(arguments, 1, arguments.length - 1);
    dest = arguments[arguments.length - 1];
  } else if (typeof sources === 'string') {
    sources = [sources];
  } else if ('length' in sources) {
    sources = sources; // no-op for array
  } else {
    error('invalid arguments');
  }

  var exists = fs.existsSync(dest),
      stats = exists && fs.statSync(dest);

  // Dest is not existing dir, but multiple sources given
  if ((!exists || !stats.isDirectory()) && sources.length > 1)
    error('dest is not a directory (too many sources)');

  // Dest is an existing file, but no -f given
  if (exists && stats.isFile() && !options.force)
    error('dest file already exists: ' + dest);

  if (options.recursive) {
    // Recursive allows the shortcut syntax "sourcedir/" for "sourcedir/*"
    // (see Github issue #15)
    sources.forEach(function(src, i) {
      if (src[src.length - 1] === '/')
        sources[i] += '*';
    });

    // Create dest
    try {
      fs.mkdirSync(dest, parseInt('0777', 8));
    } catch (e) {
      // like Unix's cp, keep going even if we can't create dest dir
    }
  }

  sources = expand(sources);

  sources.forEach(function(src) {
    if (!fs.existsSync(src)) {
      error('no such file or directory: '+src, true);
      return; // skip file
    }

    // If here, src exists
    if (fs.statSync(src).isDirectory()) {
      if (!options.recursive) {
        // Non-Recursive
        log(src + ' is a directory (not copied)');
      } else {
        // Recursive
        // 'cp /a/source dest' should create 'source' in 'dest'
        var newDest = path.join(dest, path.basename(src)),
            checkDir = fs.statSync(src);
        try {
          fs.mkdirSync(newDest, checkDir.mode);
        } catch (e) {
          //if the directory already exists, that's okay
          if (e.code !== 'EEXIST') throw e;
        }

        cpdirSyncRecursive(src, newDest, {force: options.force});
      }
      return; // done with dir
    }

    // If here, src is a file

    // When copying to '/path/dir':
    //    thisDest = '/path/dir/file1'
    var thisDest = dest;
    if (fs.existsSync(dest) && fs.statSync(dest).isDirectory())
      thisDest = path.normalize(dest + '/' + path.basename(src));

    if (fs.existsSync(thisDest) && !options.force) {
      error('dest file already exists: ' + thisDest, true);
      return; // skip file
    }

    copyFileSync(src, thisDest);
  }); // forEach(src)
}
exports.cp = wrap('cp', _cp);

//@
//@ ### rm([options ,] file [, file ...])
//@ ### rm([options ,] file_array)
//@ Available options:
//@
//@ + `-f`: force
//@ + `-r, -R`: recursive
//@
//@ Examples:
//@
//@ ```javascript
//@ rm('-rf', '/tmp/*');
//@ rm('some_file.txt', 'another_file.txt');
//@ rm(['some_file.txt', 'another_file.txt']); // same as above
//@ ```
//@
//@ Removes files. The wildcard `*` is accepted.
function _rm(options, files) {
  options = parseOptions(options, {
    'f': 'force',
    'r': 'recursive',
    'R': 'recursive'
  });
  if (!files)
    error('no paths given');

  if (typeof files === 'string')
    files = [].slice.call(arguments, 1);
  // if it's array leave it as it is

  files = expand(files);

  files.forEach(function(file) {
    if (!fs.existsSync(file)) {
      // Path does not exist, no force flag given
      if (!options.force)
        error('no such file or directory: '+file, true);

      return; // skip file
    }

    // If here, path exists

    var stats = fs.statSync(file);
    // Remove simple file
    if (stats.isFile()) {

      // Do not check for file writing permissions
      if (options.force) {
        _unlinkSync(file);
        return;
      }

      if (isWriteable(file))
        _unlinkSync(file);
      else
        error('permission denied: '+file, true);

      return;
    } // simple file

    // Path is an existing directory, but no -r flag given
    if (stats.isDirectory() && !options.recursive) {
      error('path is a directory', true);
      return; // skip path
    }

    // Recursively remove existing directory
    if (stats.isDirectory() && options.recursive) {
      rmdirSyncRecursive(file, options.force);
    }
  }); // forEach(file)
} // rm
exports.rm = wrap('rm', _rm);

//@
//@ ### mv(source [, source ...], dest')
//@ ### mv(source_array, dest')
//@ Available options:
//@
//@ + `f`: force
//@
//@ Examples:
//@
//@ ```javascript
//@ mv('-f', 'file', 'dir/');
//@ mv('file1', 'file2', 'dir/');
//@ mv(['file1', 'file2'], 'dir/'); // same as above
//@ ```
//@
//@ Moves files. The wildcard `*` is accepted.
function _mv(options, sources, dest) {
  options = parseOptions(options, {
    'f': 'force'
  });

  // Get sources, dest
  if (arguments.length < 3) {
    error('missing <source> and/or <dest>');
  } else if (arguments.length > 3) {
    sources = [].slice.call(arguments, 1, arguments.length - 1);
    dest = arguments[arguments.length - 1];
  } else if (typeof sources === 'string') {
    sources = [sources];
  } else if ('length' in sources) {
    sources = sources; // no-op for array
  } else {
    error('invalid arguments');
  }

  sources = expand(sources);

  var exists = fs.existsSync(dest),
      stats = exists && fs.statSync(dest);

  // Dest is not existing dir, but multiple sources given
  if ((!exists || !stats.isDirectory()) && sources.length > 1)
    error('dest is not a directory (too many sources)');

  // Dest is an existing file, but no -f given
  if (exists && stats.isFile() && !options.force)
    error('dest file already exists: ' + dest);

  sources.forEach(function(src) {
    if (!fs.existsSync(src)) {
      error('no such file or directory: '+src, true);
      return; // skip file
    }

    // If here, src exists

    // When copying to '/path/dir':
    //    thisDest = '/path/dir/file1'
    var thisDest = dest;
    if (fs.existsSync(dest) && fs.statSync(dest).isDirectory())
      thisDest = path.normalize(dest + '/' + path.basename(src));

    if (fs.existsSync(thisDest) && !options.force) {
      error('dest file already exists: ' + thisDest, true);
      return; // skip file
    }

    if (path.resolve(src) === path.dirname(path.resolve(thisDest))) {
      error('cannot move to self: '+src, true);
      return; // skip file
    }

    fs.renameSync(src, thisDest);
  }); // forEach(src)
} // mv
exports.mv = wrap('mv', _mv);

//@
//@ ### mkdir([options ,] dir [, dir ...])
//@ ### mkdir([options ,] dir_array)
//@ Available options:
//@
//@ + `p`: full path (will create intermediate dirs if necessary)
//@
//@ Examples:
//@
//@ ```javascript
//@ mkdir('-p', '/tmp/a/b/c/d', '/tmp/e/f/g');
//@ mkdir('-p', ['/tmp/a/b/c/d', '/tmp/e/f/g']); // same as above
//@ ```
//@
//@ Creates directories.
function _mkdir(options, dirs) {
  options = parseOptions(options, {
    'p': 'fullpath'
  });
  if (!dirs)
    error('no paths given');

  if (typeof dirs === 'string')
    dirs = [].slice.call(arguments, 1);
  // if it's array leave it as it is

  dirs.forEach(function(dir) {
    if (fs.existsSync(dir)) {
      if (!options.fullpath)
          error('path already exists: ' + dir, true);
      return; // skip dir
    }

    // Base dir does not exist, and no -p option given
    var baseDir = path.dirname(dir);
    if (!fs.existsSync(baseDir) && !options.fullpath) {
      error('no such file or directory: ' + baseDir, true);
      return; // skip dir
    }

    if (options.fullpath)
      mkdirSyncRecursive(dir);
    else
      fs.mkdirSync(dir, parseInt('0777', 8));
  });
} // mkdir
exports.mkdir = wrap('mkdir', _mkdir);

//@
//@ ### test(expression)
//@ Available expression primaries:
//@
//@ + `'-b', 'path'`: true if path is a block device
//@ + `'-c', 'path'`: true if path is a character device
//@ + `'-d', 'path'`: true if path is a directory
//@ + `'-e', 'path'`: true if path exists
//@ + `'-f', 'path'`: true if path is a regular file
//@ + `'-L', 'path'`: true if path is a symboilc link
//@ + `'-p', 'path'`: true if path is a pipe (FIFO)
//@ + `'-S', 'path'`: true if path is a socket
//@
//@ Examples:
//@
//@ ```javascript
//@ if (test('-d', path)) { /* do something with dir */ };
//@ if (!test('-f', path)) continue; // skip if it's a regular file
//@ ```
//@
//@ Evaluates expression using the available primaries and returns corresponding value.
function _test(options, path) {
  if (!path)
    error('no path given');

  // hack - only works with unary primaries
  options = parseOptions(options, {
    'b': 'block',
    'c': 'character',
    'd': 'directory',
    'e': 'exists',
    'f': 'file',
    'L': 'link',
    'p': 'pipe',
    'S': 'socket'
  });

  var canInterpret = false;
  for (var key in options)
    if (options[key] === true) {
      canInterpret = true;
      break;
    }

  if (!canInterpret)
    error('could not interpret expression');

  if (options.link) {
    try {
      return fs.lstatSync(path).isSymbolicLink();
    } catch(e) {
      return false;
    }
  }

  if (!fs.existsSync(path))
    return false;

  if (options.exists)
    return true;

  var stats = fs.statSync(path);

  if (options.block)
    return stats.isBlockDevice();

  if (options.character)
    return stats.isCharacterDevice();

  if (options.directory)
    return stats.isDirectory();

  if (options.file)
    return stats.isFile();

  if (options.pipe)
    return stats.isFIFO();

  if (options.socket)
    return stats.isSocket();
} // test
exports.test = wrap('test', _test);


//@
//@ ### cat(file [, file ...])
//@ ### cat(file_array)
//@
//@ Examples:
//@
//@ ```javascript
//@ var str = cat('file*.txt');
//@ var str = cat('file1', 'file2');
//@ var str = cat(['file1', 'file2']); // same as above
//@ ```
//@
//@ Returns a string containing the given file, or a concatenated string
//@ containing the files if more than one file is given (a new line character is
//@ introduced between each file). Wildcard `*` accepted.
function _cat(options, files) {
  var cat = '';

  if (!files)
    error('no paths given');

  if (typeof files === 'string')
    files = [].slice.call(arguments, 1);
  // if it's array leave it as it is

  files = expand(files);

  files.forEach(function(file) {
    if (!fs.existsSync(file))
      error('no such file or directory: ' + file);

    cat += fs.readFileSync(file, 'utf8') + '\n';
  });

  if (cat[cat.length-1] === '\n')
    cat = cat.substring(0, cat.length-1);

  return ShellString(cat);
}
exports.cat = wrap('cat', _cat);

//@
//@ ### 'string'.to(file)
//@
//@ Examples:
//@
//@ ```javascript
//@ cat('input.txt').to('output.txt');
//@ ```
//@
//@ Analogous to the redirection operator `>` in Unix, but works with JavaScript strings (such as
//@ those returned by `cat`, `grep`, etc). _Like Unix redirections, `to()` will overwrite any existing file!_
function _to(options, file) {
  if (!file)
    error('wrong arguments');

  if (!fs.existsSync( path.dirname(file) ))
      error('no such file or directory: ' + path.dirname(file));

  try {
    fs.writeFileSync(file, this.toString(), 'utf8');
  } catch(e) {
    error('could not write to file (code '+e.code+'): '+file, true);
  }
}
// In the future, when Proxies are default, we can add methods like `.to()` to primitive strings.
// For now, this is a dummy function to bookmark places we need such strings
function ShellString(str) {
  return str;
}
String.prototype.to = wrap('to', _to);

//@
//@ ### sed([options ,] search_regex, replace_str, file)
//@ Available options:
//@
//@ + `-i`: Replace contents of 'file' in-place. _Note that no backups will be created!_
//@
//@ Examples:
//@
//@ ```javascript
//@ sed('-i', 'PROGRAM_VERSION', 'v0.1.3', 'source.js');
//@ sed(/.*DELETE_THIS_LINE.*\n/, '', 'source.js');
//@ ```
//@
//@ Reads an input string from `file` and performs a JavaScript `replace()` on the input
//@ using the given search regex and replacement string. Returns the new string after replacement.
function _sed(options, regex, replacement, file) {
  options = parseOptions(options, {
    'i': 'inplace'
  });

  if (typeof replacement === 'string')
    replacement = replacement; // no-op
  else if (typeof replacement === 'number')
    replacement = replacement.toString(); // fallback
  else
    error('invalid replacement string');

  if (!file)
    error('no file given');

  if (!fs.existsSync(file))
    error('no such file or directory: ' + file);

  var result = fs.readFileSync(file, 'utf8').replace(regex, replacement);
  if (options.inplace)
    fs.writeFileSync(file, result, 'utf8');

  return ShellString(result);
}
exports.sed = wrap('sed', _sed);

//@
//@ ### grep([options ,] regex_filter, file [, file ...])
//@ ### grep([options ,] regex_filter, file_array)
//@ Available options:
//@
//@ + `-v`: Inverse the sense of the regex and print the lines not matching the criteria.
//@
//@ Examples:
//@
//@ ```javascript
//@ grep('-v', 'GLOBAL_VARIABLE', '*.js');
//@ grep('GLOBAL_VARIABLE', '*.js');
//@ ```
//@
//@ Reads input string from given files and returns a string containing all lines of the
//@ file that match the given `regex_filter`. Wildcard `*` accepted.
function _grep(options, regex, files) {
  options = parseOptions(options, {
    'v': 'inverse'
  });

  if (!files)
    error('no paths given');

  if (typeof files === 'string')
    files = [].slice.call(arguments, 2);
  // if it's array leave it as it is

  files = expand(files);

  var grep = '';
  files.forEach(function(file) {
    if (!fs.existsSync(file)) {
      error('no such file or directory: ' + file, true);
      return;
    }

    var contents = fs.readFileSync(file, 'utf8'),
        lines = contents.split(/\r*\n/);
    lines.forEach(function(line) {
      var matched = line.match(regex);
      if ((options.inverse && !matched) || (!options.inverse && matched))
        grep += line + '\n';
    });
  });

  return ShellString(grep);
}
exports.grep = wrap('grep', _grep);


//@
//@ ### which(command)
//@
//@ Examples:
//@
//@ ```javascript
//@ var nodeExec = which('node');
//@ ```
//@
//@ Searches for `command` in the system's PATH. On Windows looks for `.exe`, `.cmd`, and `.bat` extensions.
//@ Returns string containing the absolute path to the command.
function _which(options, cmd) {
  if (!cmd)
    error('must specify command');

  var pathEnv = process.env.path || process.env.Path || process.env.PATH,
      pathArray = splitPath(pathEnv),
      where = null;

  if(platform === 'win') {
    pathArray = ["C:\\Windows\\SysWOW64\\", "C:\\Windows\\System32\\"].concat(pathArray);
  }

  // No relative/absolute paths provided?
  if (cmd.search(/\//) === -1) {
    // Search for command in PATH
    pathArray.forEach(function(dir) {
      if (where)
        return; // already found it

      var attempt = path.resolve(dir + '/' + cmd);
      if (fs.existsSync(attempt)) {
        where = attempt;
        return;
      }

      if (platform === 'win') {
        var baseAttempt = attempt;
        attempt = baseAttempt + '.exe';
        if (fs.existsSync(attempt)) {
          where = attempt;
          return;
        }
        attempt = baseAttempt + '.cmd';
        if (fs.existsSync(attempt)) {
          where = attempt;
          return;
        }
        attempt = baseAttempt + '.bat';
        if (fs.existsSync(attempt)) {
          where = attempt;
          return;
        }
      } // if 'win'
    });
  }

  // Command not found anywhere?
  if (!fs.existsSync(cmd) && !where)
    return null;

  where = where || path.resolve(cmd);

  return ShellString(where);
}
exports.which = wrap('which', _which);

//@
//@ ### echo(string [,string ...])
//@
//@ Examples:
//@
//@ ```javascript
//@ echo('hello world');
//@ var str = echo('hello world');
//@ ```
//@
//@ Prints string to stdout, and returns string with additional utility methods
//@ like `.to()`.
function _echo() {
  var messages = [].slice.call(arguments, 0);
  console.log.apply(this, messages);
  return ShellString(messages.join(' '));
}
exports.echo = _echo; // don't wrap() as it could parse '-options'

// Pushd/popd/dirs internals
var _dirStack = [];

function _isStackIndex(index) {
  return (/^[\-+]\d+$/).test(index);
}

function _parseStackIndex(index) {
  if (_isStackIndex(index)) {
    if (Math.abs(index) < _dirStack.length + 1) { // +1 for pwd
      return (/^-/).test(index) ? Number(index) - 1 : Number(index);
    } else {
      error(index + ': directory stack index out of range');
    }
  } else {
    error(index + ': invalid number');
  }
}

function _actualDirStack() {
  return [process.cwd()].concat(_dirStack);
}

//@
//@ ### dirs([options | '+N' | '-N'])
//@
//@ Available options:
//@
//@ + `-c`: Clears the directory stack by deleting all of the elements.
//@
//@ Arguments:
//@
//@ + `+N`: Displays the Nth directory (counting from the left of the list printed by dirs when invoked without options), starting with zero.
//@ + `-N`: Displays the Nth directory (counting from the right of the list printed by dirs when invoked without options), starting with zero.
//@
//@ Display the list of currently remembered directories. Returns an array of paths in the stack, or a single path if +N or -N was specified.
//@
//@ See also: pushd, popd
function _dirs(options, index) {
  if (_isStackIndex(options)) {
    index = options;
    options = '';
  }

  options = parseOptions(options, {
    'c' : 'clear'
  });

  if (options['clear']) {
    _dirStack = [];
    return _dirStack;
  }

  var stack = _actualDirStack();

  if (index) {
    index = _parseStackIndex(index);

    if (index < 0) {
      index = stack.length + index;
    }

    log(stack[index]);
    return stack[index];
  }

  log(stack.join(' '));

  return stack;
}
exports.dirs = wrap("dirs", _dirs);

//@
//@ ### pushd([options,] [dir | '-N' | '+N'])
//@
//@ Available options:
//@
//@ + `-n`: Suppresses the normal change of directory when adding directories to the stack, so that only the stack is manipulated.
//@
//@ Arguments:
//@
//@ + `dir`: Makes the current working directory be the top of the stack, and then executes the equivalent of `cd dir`.
//@ + `+N`: Brings the Nth directory (counting from the left of the list printed by dirs, starting with zero) to the top of the list by rotating the stack.
//@ + `-N`: Brings the Nth directory (counting from the right of the list printed by dirs, starting with zero) to the top of the list by rotating the stack.
//@
//@ Examples:
//@
//@ ```javascript
//@ // process.cwd() === '/usr'
//@ pushd('/etc'); // Returns /etc /usr
//@ pushd('+1');   // Returns /usr /etc
//@ ```
//@
//@ Save the current directory on the top of the directory stack and then cd to `dir`. With no arguments, pushd exchanges the top two directories. Returns an array of paths in the stack.
function _pushd(options, dir) {
  if (_isStackIndex(options)) {
    dir = options;
    options = '';
  }

  options = parseOptions(options, {
    'n' : 'no-cd'
  });

  var dirs = _actualDirStack();

  if (dir === '+0') {
    return dirs; // +0 is a noop
  } else if (!dir) {
    if (dirs.length > 1) {
      dirs = dirs.splice(1, 1).concat(dirs);
    } else {
      return error('no other directory');
    }
  } else if (_isStackIndex(dir)) {
    var n = _parseStackIndex(dir);
    dirs = dirs.slice(n).concat(dirs.slice(0, n));
  } else {
    if (options['no-cd']) {
      dirs.splice(1, 0, dir);
    } else {
      dirs.unshift(dir);
    }
  }

  if (options['no-cd']) {
    dirs = dirs.slice(1);
  } else {
    dir = path.resolve(dirs.shift());
    _cd('', dir);
  }

  _dirStack = dirs;
  return _dirs('');
}
exports.pushd = wrap('pushd', _pushd);

//@
//@ ### popd([options,] ['-N' | '+N'])
//@
//@ Available options:
//@
//@ + `-n`: Suppresses the normal change of directory when removing directories from the stack, so that only the stack is manipulated.
//@
//@ Arguments:
//@
//@ + `+N`: Removes the Nth directory (counting from the left of the list printed by dirs), starting with zero.
//@ + `-N`: Removes the Nth directory (counting from the right of the list printed by dirs), starting with zero.
//@
//@ Examples:
//@
//@ ```javascript
//@ echo(process.cwd()); // '/usr'
//@ pushd('/etc');       // '/etc /usr'
//@ echo(process.cwd()); // '/etc'
//@ popd();              // '/usr'
//@ echo(process.cwd()); // '/usr'
//@ ```
//@
//@ When no arguments are given, popd removes the top directory from the stack and performs a cd to the new top directory. The elements are numbered from 0 starting at the first directory listed with dirs; i.e., popd is equivalent to popd +0. Returns an array of paths in the stack.
function _popd(options, index) {
  if (_isStackIndex(options)) {
    index = options;
    options = '';
  }

  options = parseOptions(options, {
    'n' : 'no-cd'
  });

  if (!_dirStack.length) {
    return error('directory stack empty');
  }

  index = _parseStackIndex(index || '+0');

  if (options['no-cd'] || index > 0 || _dirStack.length + index === 0) {
    index = index > 0 ? index - 1 : index;
    _dirStack.splice(index, 1);
  } else {
    var dir = path.resolve(_dirStack.shift());
    _cd('', dir);
  }

  return _dirs('');
}
exports.popd = wrap("popd", _popd);

//@
//@ ### exit(code)
//@ Exits the current process with the given exit code.
exports.exit = process.exit;

//@
//@ ### env['VAR_NAME']
//@ Object containing environment variables (both getter and setter). Shortcut to process.env.
exports.env = process.env;

//@
//@ ### exec(command [, options] [, callback])
//@ Available options (all `false` by default):
//@
//@ + `async`: Asynchronous execution. Defaults to true if a callback is provided.
//@ + `silent`: Do not echo program output to console.
//@
//@ Examples:
//@
//@ ```javascript
//@ var version = exec('node --version', {silent:true}).output;
//@
//@ var child = exec('some_long_running_process', {async:true});
//@ child.stdout.on('data', function(data) {
//@   /* ... do something with data ... */
//@ });
//@
//@ exec('some_long_running_process', function(code, output) {
//@   console.log('Exit code:', code);
//@   console.log('Program output:', output);
//@ });
//@ ```
//@
//@ Executes the given `command` _synchronously_, unless otherwise specified.
//@ When in synchronous mode returns the object `{ code:..., output:... }`, containing the program's
//@ `output` (stdout + stderr)  and its exit `code`. Otherwise returns the child process object, and
//@ the `callback` gets the arguments `(code, output)`.
//@
//@ **Note:** For long-lived processes, it's best to run `exec()` asynchronously as
//@ the current synchronous implementation uses a lot of CPU. This should be getting
//@ fixed soon.
function _exec(command, options, callback) {
  if (!command)
    error('must specify command');

  // Callback is defined instead of options.
  if (typeof options === 'function') {
    callback = options;
    options = { async: true };
  }

  // Callback is defined with options.
  if (typeof options === 'object' && typeof callback === 'function') {
    options.async = true;
  }

  options = extend({
    silent: config.silent,
    async: false
  }, options);

  if (options.async)
    return execAsync(command, options, callback);
  else
    return execSync(command, options);
}
exports.exec = wrap('exec', _exec, {notUnix:true});

var PERMS = (function (base) {
  return {
    OTHER_EXEC  : base.EXEC,
    OTHER_WRITE : base.WRITE,
    OTHER_READ  : base.READ,

    GROUP_EXEC  : base.EXEC  << 3,
    GROUP_WRITE : base.WRITE << 3,
    GROUP_READ  : base.READ << 3,

    OWNER_EXEC  : base.EXEC << 6,
    OWNER_WRITE : base.WRITE << 6,
    OWNER_READ  : base.READ << 6,

    // Literal octal numbers are apparently not allowed in "strict" javascript.  Using parseInt is
    // the preferred way, else a jshint warning is thrown.
    STICKY      : parseInt('01000', 8),
    SETGID      : parseInt('02000', 8),
    SETUID      : parseInt('04000', 8),

    TYPE_MASK   : parseInt('0770000', 8)
  };
})({
  EXEC  : 1,
  WRITE : 2,
  READ  : 4
});


//@
//@ ### chmod(octal_mode || octal_string, file)
//@ ### chmod(symbolic_mode, file)
//@
//@ Available options:
//@
//@ + `-v`: output a diagnostic for every file processed//@
//@ + `-c`: like verbose but report only when a change is made//@
//@ + `-R`: change files and directories recursively//@
//@
//@ Examples:
//@
//@ ```javascript
//@ chmod(755, '/Users/brandon');
//@ chmod('755', '/Users/brandon'); // same as above
//@ chmod('u+x', '/Users/brandon');
//@ ```
//@
//@ Alters the permissions of a file or directory by either specifying the
//@ absolute permissions in octal form or expressing the changes in symbols.
//@ This command tries to mimic the POSIX behavior as much as possible.
//@ Notable exceptions:
//@
//@ + In symbolic modes, 'a-r' and '-r' are identical.  No consideration is
//@   given to the umask.
//@ + There is no "quiet" option since default behavior is to run silent.
function _chmod(options, mode, filePattern) {
  if (!filePattern) {
    if (options.length > 0 && options.charAt(0) === '-') {
      // Special case where the specified file permissions started with - to subtract perms, which
      // get picked up by the option parser as command flags.
      // If we are down by one argument and options starts with -, shift everything over.
      filePattern = mode;
      mode = options;
      options = '';
    }
    else {
      error('You must specify a file.');
    }
  }

  options = parseOptions(options, {
    'R': 'recursive',
    'c': 'changes',
    'v': 'verbose'
  });

  if (typeof filePattern === 'string') {
    filePattern = [ filePattern ];
  }

  var files;

  if (options.recursive) {
    files = [];
    expand(filePattern).forEach(function addFile(expandedFile) {
      var stat = fs.lstatSync(expandedFile);

      if (!stat.isSymbolicLink()) {
        files.push(expandedFile);

        if (stat.isDirectory()) {  // intentionally does not follow symlinks.
          fs.readdirSync(expandedFile).forEach(function (child) {
            addFile(expandedFile + '/' + child);
          });
        }
      }
    });
  }
  else {
    files = expand(filePattern);
  }

  files.forEach(function innerChmod(file) {
    file = path.resolve(file);
    if (!fs.existsSync(file)) {
      error('File not found: ' + file);
    }

    // When recursing, don't follow symlinks.
    if (options.recursive && fs.lstatSync(file).isSymbolicLink()) {
      return;
    }

    var perms = fs.statSync(file).mode;
    var type = perms & PERMS.TYPE_MASK;

    var newPerms = perms;

    if (isNaN(parseInt(mode, 8))) {
      // parse options
      mode.split(',').forEach(function (symbolicMode) {
        /*jshint regexdash:true */
        var pattern = /([ugoa]*)([=\+-])([rwxXst]*)/i;
        var matches = pattern.exec(symbolicMode);

        if (matches) {
          var applyTo = matches[1];
          var operator = matches[2];
          var change = matches[3];

          var changeOwner = applyTo.indexOf('u') != -1 || applyTo === 'a' || applyTo === '';
          var changeGroup = applyTo.indexOf('g') != -1 || applyTo === 'a' || applyTo === '';
          var changeOther = applyTo.indexOf('o') != -1 || applyTo === 'a' || applyTo === '';

          var changeRead   = change.indexOf('r') != -1;
          var changeWrite  = change.indexOf('w') != -1;
          var changeExec   = change.indexOf('x') != -1;
          var changeSticky = change.indexOf('t') != -1;
          var changeSetuid = change.indexOf('s') != -1;

          var mask = 0;
          if (changeOwner) {
            mask |= (changeRead ? PERMS.OWNER_READ : 0) + (changeWrite ? PERMS.OWNER_WRITE : 0) + (changeExec ? PERMS.OWNER_EXEC : 0) + (changeSetuid ? PERMS.SETUID : 0);
          }
          if (changeGroup) {
            mask |= (changeRead ? PERMS.GROUP_READ : 0) + (changeWrite ? PERMS.GROUP_WRITE : 0) + (changeExec ? PERMS.GROUP_EXEC : 0) + (changeSetuid ? PERMS.SETGID : 0);
          }
          if (changeOther) {
            mask |= (changeRead ? PERMS.OTHER_READ : 0) + (changeWrite ? PERMS.OTHER_WRITE : 0) + (changeExec ? PERMS.OTHER_EXEC : 0);
          }

          // Sticky bit is special - it's not tied to user, group or other.
          if (changeSticky) {
            mask |= PERMS.STICKY;
          }

          switch (operator) {
            case '+':
              newPerms |= mask;
              break;

            case '-':
              newPerms &= ~mask;
              break;

            case '=':
              newPerms = type + mask;

              // According to POSIX, when using = to explicitly set the permissions, setuid and setgid can never be cleared.
              if (fs.statSync(file).isDirectory()) {
                newPerms |= (PERMS.SETUID + PERMS.SETGID) & perms;
              }
              break;
          }

          if (options.verbose) {
            log(file + ' -> ' + newPerms.toString(8));
          }

          if (perms != newPerms) {
            if (!options.verbose && options.changes) {
              log(file + ' -> ' + newPerms.toString(8));
            }
            fs.chmodSync(file, newPerms);
          }
        }
        else {
          error('Invalid symbolic mode change: ' + symbolicMode);
        }
      });
    }
    else {
      // they gave us a full number
      newPerms = type + parseInt(mode, 8);

      // POSIX rules are that setuid and setgid can only be added using numeric form, but not cleared.
      if (fs.statSync(file).isDirectory()) {
        newPerms |= (PERMS.SETUID + PERMS.SETGID) & perms;
      }

      fs.chmodSync(file, newPerms);
    }
  });
}
exports.chmod = wrap('chmod', _chmod);


//@
//@ ## Configuration
//@



exports.config = config;

//@
//@ ### config.silent
//@ Example:
//@
//@ ```javascript
//@ var silentState = config.silent; // save old silent state
//@ config.silent = true;
//@ /* ... */
//@ config.silent = silentState; // restore old silent state
//@ ```
//@
//@ Suppresses all command output if `true`, except for `echo()` calls.
//@ Default is `false`.

//@
//@ ### config.fatal
//@ Example:
//@
//@ ```javascript
//@ config.fatal = true;
//@ cp('this_file_does_not_exist', '/dev/null'); // dies here
//@ /* more commands... */
//@ ```
//@
//@ If `true` the script will die on errors. Default is `false`.




//@
//@ ## Non-Unix commands
//@






//@
//@ ### tempdir()
//@ Searches and returns string containing a writeable, platform-dependent temporary directory.
//@ Follows Python's [tempfile algorithm](http://docs.python.org/library/tempfile.html#tempfile.tempdir).
exports.tempdir = wrap('tempdir', tempDir);


//@
//@ ### error()
//@ Tests if error occurred in the last command. Returns `null` if no error occurred,
//@ otherwise returns string explaining the error
exports.error = function() {
  return state.error;
};





////////////////////////////////////////////////////////////////////////////////////////////////
//
// Auxiliary functions (internal use only)
//

function log() {
  if (!config.silent)
    console.log.apply(this, arguments);
}

function deprecate(what, msg) {
  console.log('*** ShellJS.'+what+': This function is deprecated.', msg);
}

function write(msg) {
  if (!config.silent)
    process.stdout.write(msg);
}

// Shows error message. Throws unless _continue or config.fatal are true
function error(msg, _continue) {
  if (state.error === null)
    state.error = '';
  state.error += state.currentCmd + ': ' + msg + '\n';

  log(state.error);

  if (config.fatal)
    process.exit(1);

  if (!_continue)
    throw '';
}

// Returns {'alice': true, 'bob': false} when passed:
//   parseOptions('-a', {'a':'alice', 'b':'bob'});
function parseOptions(str, map) {
  if (!map)
    error('parseOptions() internal error: no map given');

  // All options are false by default
  var options = {};
  for (var letter in map)
    options[map[letter]] = false;

  if (!str)
    return options; // defaults

  if (typeof str !== 'string')
    error('parseOptions() internal error: wrong str');

  // e.g. match[1] = 'Rf' for str = '-Rf'
  var match = str.match(/^\-(.+)/);
  if (!match)
    return options;

  // e.g. chars = ['R', 'f']
  var chars = match[1].split('');

  chars.forEach(function(c) {
    if (c in map)
      options[map[c]] = true;
    else
      error('option not recognized: '+c);
  });

  return options;
}

// Common wrapper for all Unix-like commands
function wrap(cmd, fn, options) {
  return function() {
    var retValue = null;

    state.currentCmd = cmd;
    state.error = null;

    try {
      var args = [].slice.call(arguments, 0);

      if (options && options.notUnix) {
        retValue = fn.apply(this, args);
      } else {
        if (args.length === 0 || typeof args[0] !== 'string' || args[0][0] !== '-')
          args.unshift(''); // only add dummy option if '-option' not already present
        retValue = fn.apply(this, args);
      }
    } catch (e) {
      if (!state.error) {
        // If state.error hasn't been set it's an error thrown by Node, not us - probably a bug...
        console.log('shell.js: internal error');
        console.log(e.stack || e);
        process.exit(1);
      }
      if (config.fatal)
        throw e;
    }

    state.currentCmd = 'shell.js';
    return retValue;
  };
} // wrap

// Buffered file copy, synchronous
// (Using readFileSync() + writeFileSync() could easily cause a memory overflow
//  with large files)
function copyFileSync(srcFile, destFile) {
  if (!fs.existsSync(srcFile))
    error('copyFileSync: no such file or directory: ' + srcFile);

  var BUF_LENGTH = 64*1024,
      buf = new Buffer(BUF_LENGTH),
      bytesRead = BUF_LENGTH,
      pos = 0,
      fdr = null,
      fdw = null;

  try {
    fdr = fs.openSync(srcFile, 'r');
  } catch(e) {
    error('copyFileSync: could not read src file ('+srcFile+')');
  }

  try {
    fdw = fs.openSync(destFile, 'w');
  } catch(e) {
    error('copyFileSync: could not write to dest file (code='+e.code+'):'+destFile);
  }

  while (bytesRead === BUF_LENGTH) {
    bytesRead = fs.readSync(fdr, buf, 0, BUF_LENGTH, pos);
    fs.writeSync(fdw, buf, 0, bytesRead);
    pos += bytesRead;
  }

  fs.closeSync(fdr);
  fs.closeSync(fdw);
}

// Recursively copies 'sourceDir' into 'destDir'
// Adapted from https://github.com/ryanmcgrath/wrench-js
//
// Copyright (c) 2010 Ryan McGrath
// Copyright (c) 2012 Artur Adib
//
// Licensed under the MIT License
// http://www.opensource.org/licenses/mit-license.php
function cpdirSyncRecursive(sourceDir, destDir, opts) {
  if (!opts) opts = {};

  /* Create the directory where all our junk is moving to; read the mode of the source directory and mirror it */
  var checkDir = fs.statSync(sourceDir);
  try {
    if(!fs.existsSync(destDir)) {
        fs.mkdirSync(destDir, checkDir.mode);
    }
  } catch (e) {
    //if the directory already exists, that's okay
    if (e.code !== 'EEXIST') throw e;
  }

  var files = fs.readdirSync(sourceDir);

  for(var i = 0; i < files.length; i++) {
    var currFile = fs.lstatSync(sourceDir + "/" + files[i]);

    if (currFile.isDirectory()) {
      /* recursion this thing right on back. */
      cpdirSyncRecursive(sourceDir + "/" + files[i], destDir + "/" + files[i], opts);
    } else if (currFile.isSymbolicLink()) {
      var symlinkFull = fs.readlinkSync(sourceDir + "/" + files[i]);
      if(fs.existsSync(destDir + "/" + files[i])) {
        fs.unlinkSync(destDir + "/" + files[i]);
      }
      fs.symlinkSync(symlinkFull, destDir + "/" + files[i]);
    } else {
      /* At this point, we've hit a file actually worth copying... so copy it on over. */
      if (fs.existsSync(destDir + "/" + files[i]) && !opts.force) {
        log('skipping existing file: ' + files[i]);
      } else {
        copyFileSync(sourceDir + "/" + files[i], destDir + "/" + files[i]);
      }
    }

  } // for files
} // cpdirSyncRecursive

// Recursively removes 'dir'
// Adapted from https://github.com/ryanmcgrath/wrench-js
//
// Copyright (c) 2010 Ryan McGrath
// Copyright (c) 2012 Artur Adib
//
// Licensed under the MIT License
// http://www.opensource.org/licenses/mit-license.php
function rmdirSyncRecursive(dir, force) {
  var files;

  files = fs.readdirSync(dir);

  // Loop through and delete everything in the sub-tree after checking it
  for(var i = 0; i < files.length; i++) {
    var file = dir + "/" + files[i],
        currFile = fs.lstatSync(file);

    if(currFile.isDirectory()) { // Recursive function back to the beginning
      rmdirSyncRecursive(file, force);
    }

    else if(currFile.isSymbolicLink()) { // Unlink symlinks
      if (force || isWriteable(file)) {
        try {
          _unlinkSync(file);
        } catch (e) {
          error('could not remove file (code '+e.code+'): ' + file, true);
        }
      }
    }

    else // Assume it's a file - perhaps a try/catch belongs here?
      if (force || isWriteable(file)) {
        try {
          _unlinkSync(file);
        } catch (e) {
          error('could not remove file (code '+e.code+'): ' + file, true);
        }
      }
  }

  // Now that we know everything in the sub-tree has been deleted, we can delete the main directory.
  // Huzzah for the shopkeep.

  var result;
  try {
    result = fs.rmdirSync(dir);
  } catch(e) {
    error('could not remove directory (code '+e.code+'): ' + dir, true);
  }

  return result;
} // rmdirSyncRecursive

// Recursively creates 'dir'
function mkdirSyncRecursive(dir) {
  var baseDir = path.dirname(dir);

  // Base dir exists, no recursion necessary
  if (fs.existsSync(baseDir)) {
    fs.mkdirSync(dir, parseInt('0777', 8));
    return;
  }

  // Base dir does not exist, go recursive
  mkdirSyncRecursive(baseDir);

  // Base dir created, can create dir
  fs.mkdirSync(dir, parseInt('0777', 8));
}

// e.g. 'shelljs_a5f185d0443ca...'
function randomFileName() {
  function randomHash(count) {
    if (count === 1)
      return parseInt(16*Math.random(), 10).toString(16);
    else {
      var hash = '';
      for (var i=0; i<count; i++)
        hash += randomHash(1);
      return hash;
    }
  }

  return 'shelljs_'+randomHash(20);
}

// Returns false if 'dir' is not a writeable directory, 'dir' otherwise
function writeableDir(dir) {
  if (!dir || !fs.existsSync(dir))
    return false;

  if (!fs.statSync(dir).isDirectory())
    return false;

  var testFile = dir+'/'+randomFileName();
  try {
    fs.writeFileSync(testFile, ' ');
    _unlinkSync(testFile);
    return dir;
  } catch (e) {
    return false;
  }
}

// Cross-platform method for getting an available temporary directory.
// Follows the algorithm of Python's tempfile.tempdir
// http://docs.python.org/library/tempfile.html#tempfile.tempdir
function tempDir() {
  if (state.tempDir)
    return state.tempDir; // from cache

  state.tempDir = writeableDir(process.env['TMPDIR']) ||
                  writeableDir(process.env['TEMP']) ||
                  writeableDir(process.env['TMP']) ||
                  writeableDir(process.env['Wimp$ScrapDir']) || // RiscOS
                  writeableDir('C:\\TEMP') || // Windows
                  writeableDir('C:\\TMP') || // Windows
                  writeableDir('\\TEMP') || // Windows
                  writeableDir('\\TMP') || // Windows
                  writeableDir('/tmp') ||
                  writeableDir('/var/tmp') ||
                  writeableDir('/usr/tmp') ||
                  writeableDir('.'); // last resort

  return state.tempDir;
}

// Wrapper around exec() to enable echoing output to console in real time
function execAsync(cmd, opts, callback) {
  var output = '';

  var options = extend({
    silent: config.silent
  }, opts);

  var c = child.exec(cmd, {env: process.env, maxBuffer: 20*1024*1024}, function(err) {
    if (callback)
      callback(err ? err.code : 0, output);
  });

  c.stdout.on('data', function(data) {
    output += data;
    if (!options.silent)
      process.stdout.write(data);
  });

  c.stderr.on('data', function(data) {
    output += data;
    if (!options.silent)
      process.stdout.write(data);
  });

  return c;
}

// Hack to run child_process.exec() synchronously (sync avoids callback hell)
// Uses a custom wait loop that checks for a flag file, created when the child process is done.
// (Can't do a wait loop that checks for internal Node variables/messages as
// Node is single-threaded; callbacks and other internal state changes are done in the
// event loop).
function execSync(cmd, opts) {
  var stdoutFile = path.resolve(tempDir()+'/'+randomFileName()),
      codeFile = path.resolve(tempDir()+'/'+randomFileName()),
      scriptFile = path.resolve(tempDir()+'/'+randomFileName()),
      sleepFile = path.resolve(tempDir()+'/'+randomFileName());

  var options = extend({
    silent: config.silent
  }, opts);

  var previousStdoutContent = '';
  // Echoes stdout changes from running process, if not silent
  function updateStdout() {
    if (options.silent || !fs.existsSync(stdoutFile))
      return;

    var stdoutContent = fs.readFileSync(stdoutFile, 'utf8');
    // No changes since last time?
    if (stdoutContent.length <= previousStdoutContent.length)
      return;

    process.stdout.write(stdoutContent.substr(previousStdoutContent.length));
    previousStdoutContent = stdoutContent;
  }

  function escape(str) {
    return (str+'').replace(/([\\"'])/g, "\\$1").replace(/\0/g, "\\0");
  }

  cmd += ' > '+stdoutFile+' 2>&1'; // works on both win/unix

  var script =
   "var child = require('child_process')," +
   "     fs = require('fs');" +
   "child.exec('"+escape(cmd)+"', {env: process.env, maxBuffer: 20*1024*1024}, function(err) {" +
   "  fs.writeFileSync('"+escape(codeFile)+"', err ? err.code.toString() : '0');" +
   "});";

  if (fs.existsSync(scriptFile)) _unlinkSync(scriptFile);
  if (fs.existsSync(stdoutFile)) _unlinkSync(stdoutFile);
  if (fs.existsSync(codeFile)) _unlinkSync(codeFile);

  fs.writeFileSync(scriptFile, script);
  child.exec('"'+process.execPath+'" '+scriptFile, {
    env: process.env,
    cwd: exports.pwd(),
    maxBuffer: 20*1024*1024
  });

  // The wait loop
  // sleepFile is used as a dummy I/O op to mitigate unnecessary CPU usage
  // (tried many I/O sync ops, writeFileSync() seems to be only one that is effective in reducing
  // CPU usage, though apparently not so much on Windows)
  while (!fs.existsSync(codeFile)) { updateStdout(); fs.writeFileSync(sleepFile, 'a'); }
  while (!fs.existsSync(stdoutFile)) { updateStdout(); fs.writeFileSync(sleepFile, 'a'); }

  // At this point codeFile exists, but it's not necessarily flushed yet.
  // Keep reading it until it is.
  var code = parseInt('', 10);
  while (isNaN(code)) {
    code = parseInt(fs.readFileSync(codeFile, 'utf8'), 10);
  }

  var stdout = fs.readFileSync(stdoutFile, 'utf8');

  // No biggie if we can't erase the files now -- they're in a temp dir anyway
  try { _unlinkSync(scriptFile); } catch(e) {}
  try { _unlinkSync(stdoutFile); } catch(e) {}
  try { _unlinkSync(codeFile); } catch(e) {}
  try { _unlinkSync(sleepFile); } catch(e) {}

  // True if successful, false if not
  var obj = {
    code: code,
    output: stdout
  };
  return obj;
} // execSync()

// Expands wildcards with matching file names. For a given array of file names 'list', returns
// another array containing all file names as per ls(list[i]).
// For example:
//   expand(['file*.js']) = ['file1.js', 'file2.js', ...]
//   (if the files 'file1.js', 'file2.js', etc, exist in the current dir)
function expand(list) {
  var expanded = [];
  list.forEach(function(listEl) {
    // Wildcard present?
    if (listEl.search(/\*/) > -1) {
      _ls('', listEl).forEach(function(file) {
        expanded.push(file);
      });
    } else {
      expanded.push(listEl);
    }
  });
  return expanded;
}

// Cross-platform method for splitting environment PATH variables
function splitPath(p) {
  if (!p)
    return [];

  if (platform === 'win')
    return p.split(';');
  else
    return p.split(':');
}

// extend(target_obj, source_obj1 [, source_obj2 ...])
// Shallow extend, e.g.:
//    extend({A:1}, {b:2}, {c:3}) returns {A:1, b:2, c:3}
function extend(target) {
  var sources = [].slice.call(arguments, 1);
  sources.forEach(function(source) {
    for (var key in source)
      target[key] = source[key];
  });

  return target;
}

// Normalizes _unlinkSync() across platforms to match Unix behavior, i.e.
// file can be unlinked even if it's read-only, see joyent/node#3006
function _unlinkSync(file) {
  try {
    fs.unlinkSync(file);
  } catch(e) {
    // Try to override file permission
    if (e.code === 'EPERM') {
      fs.chmodSync(file, '0666');
      fs.unlinkSync(file);
    } else {
      throw e;
    }
  }
}

// Hack to determine if file has write permissions for current user
// Avoids having to check user, group, etc, but it's probably slow
function isWriteable(file) {
  var writePermission = true;
  try {
    var __fd = fs.openSync(file, 'a');
    fs.closeSync(__fd);
  } catch(e) {
    writePermission = false;
  }

  return writePermission;
}
