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https://github.com/danielstjules/pjs

Pipeable javascript. Quickly filter, map, and reduce from the terminal
https://github.com/danielstjules/pjs

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Pipeable javascript. Quickly filter, map, and reduce from the terminal

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README 

        
![pjs](http://danielstjules.com/github/pjs-logo.png)



Pipeable JavaScript - another utility like sed/awk/wc... but with JS! Quickly

filter, map and reduce from the command line. Features a streaming API.

Inspired by pipeable ruby.



[![Build Status](https://api.travis-ci.org/danielstjules/pjs.svg?branch=master)](https://travis-ci.org/danielstjules/pjs)



## Overview



pjs is a cli tool that can accept input on stdin, or read from a list of files.

Its filter, map and reduce options take expressions to be run, in that order,

and applies them to the supplied input. The expressions themselves can contain

identifiers used by keys in String.prototype, which will automatically be bound

to the given line. This lets you save a bit of typing with your one-liners,

while still giving you access to all your JS string functions! Check out some

of the examples below to see how they translate.



``` bash

# Return all lines longer than 5 chars

# => lines.filter(function(line) { return line.length > 5; });

ls -1 | pjs -f 'length > 5'



# Count characters in each line

# => lines.map(function(line) { return line.length; });

ls -1 | pjs -m 'length'



# Uppercase and pad each line

# => lines.map(function(line) { return '  ' + line.toUpperCase()"; });

ls -1 | pjs -m '"  " + toUpperCase()'



# Return lines longer than 5 chars, and remove any digits

# => lines

#      .filter(function(line) { return line.length > 5; })

#      .map(function(line) { return line.replace(/\d/g, ''); });

ls -1 | pjs -f 'length > 5' -m 'replace(/\d/g, "")'

```



The current line and value can also be accessed via the `$` variable, and the

tool supports json output.



``` bash

(echo 'foo' && echo 'foobar') | pjs -jm '{name: $, length: length}'

[

{"name":"foo","length":3},

{"name":"foobar","length":6}

]

```



pjs also includes lodash functions, which can be accessed via the `_` object,

and chained using $$



``` bash

echo 'hello' | pjs -m '_.upperFirst($)'

# Hello



echo 'please-titleize-this-sentence' | \

pjs -m '$$.lowerCase().split(" ").map(_.upperFirst).join(" ")'

# Please Titleize This Sentence

```



as well as Ramda and point-free style



``` bash

echo 'please-titleize-this-sentence' | \

pjs -m "R.compose(R.replace(/(^|\s)\w/g, R.toUpper), R.replace(/-/g, ' '))"

# Please Titleize This Sentence

```



## Installation



It can be installed via `npm` using:



```

npm install -g pipeable-js

```



## Usage



```

Usage: pjs [options] [files ...]



Functions and expressions are invoked in the following order:

filter, map, reduce



All functions are passed the line ($) and index (i)

Built-in reduce functions: length, min, max, sum, avg, concat

Custom reduce expressions accept: prev, curr, i, array

Includes lodash (_), and can be chained using $$

Supports Ramda (R) and point-free style



Options:



  -h, --help               output usage information

  -V, --version            output the version number

  -i, --ignore             ignore empty lines

  -j, --json               output as json

  -f, --filter        filter by a boolean expression

  -m, --map           map values using the expression

  -r, --reduce   reduce using a function or expression

```



## Examples



### filter



``` bash

# Print all odd lines

# awk 'NR % 2 == 1' file

pjs -f 'i % 2 == 0' file



# Print all lines greater than 80 chars in length

# awk 'length($0) > 80' file

pjs -f 'length > 80' file

```



### map



``` bash

# Remove all digits

# tr -d 0-9 < file

pjs -m "replace(/\d/g, '')" file



# Get second item of each line in csv

# awk -F "," '{print $2}' file

pjs -m 'split(",")[1]' file

```



### reduce



``` bash

# Count lines in file

# wc -l file

# awk 'END { print NR }' file

pjs -r length file



# Sum all decimal numbers in a file

# awk '{ sum += $1 } END { print sum }' file

# perl -nle '$sum += $_ } END { print $sum' file

pjs -r 'Number(prev) + Number(curr)' file

pjs -r '(+prev) + (+curr)' file

pjs -r sum file



# Concatenate all lines in multiple files

# awk '{printf $0;}' file1 file2

# cat file1 file2 | tr -d '\n'

pjs -r concat file1 file2

```



### mixed



``` bash

# Print the length of the longest line

# awk '{ if (length($0) > max) max = length($0) } END { print max }' file

pjs -m 'length' -r max file

```



## Comparison



| Features              | pjs        | pythonpy               | pru        |

|-----------------------|------------|------------------------|------------|

| Language              | JavaScript | Python                 | Ruby       |

| Streaming             | Yes        | Limited [1] | Yes        |

| Implementation        | Streams    | Iterables              | Generators |

| Easy JSON output      | Yes        | No                     | No         |

| WebscaleTM | YES        | No                     | No         |



[1] Can't perform "tail -f logfile | py -x x"