text: var common = require('./common');
  var fs = require('fs');
  
  common.register('grep', _grep, {
      globStart: 2, // don't glob-expand the regex
      canReceivePipe: true,
      cmdOptions: {
          'v': 'inverse',
          'l': 'nameOnly',
      },
  });
  
  //@
  //@ ### 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.
  //@ + `-l`: Print only filenames of matching files
  //@
  //@ 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`.
  function _grep(options, regex, files) {
      // Check if this is coming from a pipe
      var pipe = common.readFromPipe();
  
      if (!files && !pipe) common.error('no paths given', 2);
  
      files = [].slice.call(arguments, 2);
  
      if (pipe) {
          files.unshift('-');
      }
  
      var grep = [];
      files.forEach(function (file) {
          if (!fs.existsSync(file) && file !== '-') {
              common.error('no such file or directory: ' + file, 2, {continue: true});
              return;
          }
  
          var contents = file === '-' ? pipe : fs.readFileSync(file, 'utf8');
          var lines = contents.split(/\r*\n/);
          if (options.nameOnly) {
              if (contents.match(regex)) {
                  grep.push(file);
              }
          } else {
              lines.forEach(function (line) {
                  var matched = line.match(regex);
                  if ((options.inverse && !matched) || (!options.inverse && matched)) {
                      grep.push(line);
                  }
              });
          }
      });
  
      return grep.join('\n') + '\n';
  }
  module.exports = _grep;
  