file-extractor

file-extractor

Extract data from text files or log files using regular expressions.

introduction

Extractor scans file line by line. Registred callbacks are notified when a patterm matches current line.

synopsis

Start extracting stdin :

    var extractor = require('file-extractor');

    extractor().matches(/;(?!(?:[^",]|[^"],[^"])+")/,function(m){
        console.log(m);
    }).start();

Using multiple patterns :

    var extractor = require('file-extractor');

    extractor()
        .matches(/regex1/, cb1)
        .matches(/regex2/, cb2)
        .matches(/regex3/, cb3).start();

Using an accumulator :

    var extractor = require('file-extractor'),
        fs = require('fs');

    var s = fs.createReadStream(__dirname + '/sample.csv',{});
    extractor({'count': 0}).matches(/;(?!(?:[^",]|[^"],[^"])+")/,function(m, vars){
        console.log(m);
        vars.count ++;
    }).on('end', function(vars){
        console.log(vars.count + ' matches found.');
    }).start(s);

Using watch mode :

    var extractor = require('file-extractor');

    extractor()
        .matches(/regex1/, cb1)
        .matches(/regex2/, cb2)
        .matches(/regex3/, cb3).watch('sample.txt');

This mode supports wildcards in file names :

    var extractor = require('file-extractor');

    extractor()
        .matches(/regex1/, cb1)
        .matches(/regex2/, cb2)
        .matches(/regex3/, cb3).watch('/var/log/*.log');

In this case an additionnal parameter is passed to the callback function to indicate which file triggered the pattern.

    var extractor = require('file-extractor');

    extractor()
        .matches(/regex3/, function(match, vars, file){
          console.log('pattern found in : ' + file);
        }).watch('/var/log/*.log');

installation

$ npm install file-extractor

API

extractor(ac={})

The constructor function creates a new extractor. Optionnaly pass an accumulator as parameter. Accumulator may be used to share data across callbacks.

.matches(regex, callback)

Register a new matching pattern and corresponding callback. Each match is notified using callback.

• First callback parameter is regex.exec result.
• Second parameter is the accumulator object.
• optionnaly the third parameter is file name (in watch mode).

Return value is this to enable method chaining.

.start(readableStream=process.stdin)

Start scanning stream and notify callbacks. If readableStream is empty use standard input process.stdin.

.watch(filename)

Start watching file filename for modification, may contains wildcard (see minimatch by @izs). Each new lines will trigger matching callbacks.

.close()

Clean up method. Remove any watcher on file.

Events

'end'

Sent when end of stream is reached. The current accumulator is given as first parameter to the event listener. Only emited in no-watch mode (start method).

'error'

Sent when watching files with wildcards (*) and an error occurred when selecting files. Only emited in watch mode (watch method).