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Javascript Terminal String Editor: NSed brings Node.js power to the command line.

It works similarly to the standard GNU sed command, with the exception that everything is Javascript and powered by Node.js.

For instance, the following command computes the hash of each file in the test folder:

find test -type f | nsed -r fs -r crypto -c 'fs.readFileSync($data, "utf8")' -c 'crypto.createHash("md5").update($data).digest("hex")'


To install, simply use npm or yarn:

npm install -g nsed


Basic usage

Each command is executed on the output of the previous one. You can reference $data for the current input and $index for the current position in the input.

If operating directly on properties or methods of the input, you can omit $data.

find test -type f | nsed -r fs -c 'fs.readFileSync($data, "utf8")' -c '.length'

To see all the available options, use -h|--help option.


Input lines can be filtered out by using filter (-f|--filter) or reverse filters (-F|--reverse-filter) that, respectively, will include the input if the result of the evaluation is a truthy or falsy value (according to Javascript rules).

For instance, the following command will print only files starting with index:

find test -type f | nsed -f '/^index/'

Regular expressions

Regular expression can be used in commands and referenced later, using $NUMBER syntax.

For instance, the following command will print the second letter of each file:

find test -type f | nsed -c '.replace("test/", "")' -c '/.(.).+/' -c '$1'

Advanced usage

Before processing commands, you can instruct nsed to require any available Node.js modules, by using -r|--require switch. The module will be available with its name camelcased. For instance, -r string_decoder will make stringDecoder available for your commands.

Finally, instead of providing commands via command line, you can input Javascript file using -s|--source switch. The source file must export a function which accepts a string ($data representing the current line) and a number ($index, representing the current line in the input).

ESM Only

This package only supports to be directly imported in a ESM context.

For informations on how to use it in a CommonJS context, please check this page.

Contributing to nsed

  • Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet.
  • Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it.
  • Fork the project.
  • Start a feature/bugfix branch.
  • Commit and push until you are happy with your contribution.
  • Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.


Copyright (C) 2017 and above Shogun

Licensed under the MIT license, which can be found at