kolodny / nip

Node Input/output Piper

nip - Node Input/output Piper

nip is a command line utility for performing any type of processing to and from files and pipes

Install

npm install nip -g

If you omit the -g then make sure to add the local npm module path to your default path

You should now be able to call nip from the command line.

Usage: nip js-function [options] [files]

The js-function can be one of three syntaxes:

1. return line.substr(0, 10) + index
2. function(line, index, cols, lines) { /* code here */ return value; }
3. /* code */ return function(line, i, cols, lines) { /* ... */ return value; }

The names line, index, lines, and cols can be changed in the second and third style syntaxes

If the return value is false nothing is sent to output stream
If the return value is not a string or number then the line will be sent to the output stream
else the return value will be sent to the output stream (including an empty string)

options

-f js-file or --file=js-file

use the js-file as the function to execute on the input instead of the js-function argument you must supply either this option or the js-function argument

---

-1 or --first-line-only

only execute once per file, not for each line
this is useful if you plan on proccessing the file as a whole, namely through the lines variable
for example (not a useful one): nip 'return lines.length' -1 file.txt

---

-c string-or-regex, --col-splitter=string-or-regex

the splitter for --cols, can be regex or string format, by default it's /\s+/

---

-s string-or-regex, --line-splitter=string-or-regex

the line separator, can be regex or string format, by default we're splitting on lines so it's \n

---

-n string, --line-joiner=string

string used to join lines together

---

Examples

Only output lines that begin with the word var:

nip 'function(l) { return /^var/.test(l); }' lines-that-start-with-var.txt

Output every second line only in uppercase in a file:

nip 'function(line, i) { return i % 2 ? line.toUpperCase() : false; }' every-2nd-line.txt

Trim whitesplace from a file:

nip 'return line.replace(/^s*|s*$/g, "");' trim-lines.txt

Run the contents of jsfile.js on file.txt:

nip -f jsfile.js file.txt

Like most unix commands, you can pipe the input and/or output:

generate a script file to rename files recursively and sequentiality
find . -type f | nip 'return "mv " + line + " " + line.replace(/\/[^/]*$/, "") + "/" + index;' > rename-script

rename files recursively and sequentiality
find . -type f | nip 'return "mv " + line + " " + line.replace(/\/[^/]*$/, "") + "/" + index;' | sh

find the biggest number from all files in a directory:

nip '
  var biggest = 0;
  this.on("end", function() { print(biggest); });
  return function(_,i,lines) {
    biggest = Math.max(biggest,
      Math.max.apply(Math, lines.match(/(?:\s|^)[\d]+(?:\.\d*)?(?:\s|$)/g))
    )
  }' -1 *

---

By default there are start, end, fileStart, and fileEnd events you can register by doing this.on('end', function() {})

The context inside the main function can be used as a global store, and has a filename property

---

Why

This is for people who aren't "devops" and who can't crank out a fancy piped shell script using awk and sed. Also most programmers who have node installed can write a quick javascript one+ liner to do what the oldschoolers would make a shell script out of.

https://github.com/kolodny/nip