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    slice-file

    1.0.0 • Public • Published

    slice-file

    stream file slices by line number indexes

    build status

    example

    positive slice

    var sf = require('slice-file');
    var words = sf('/usr/share/dict/words');
    words.slice(22398,22408).pipe(process.stdout);
    beep
    beep's
    beeped
    beeper
    beeper's
    beepers
    beeping
    beeps
    beer
    beer's
    

    tail

    var sf = require('slice-file');
    var xs = sf('/usr/share/dict/words');
    xs.slice(-10).pipe(process.stdout);
    élan's
    émigré
    émigré's
    émigrés
    épée
    épée's
    épées
    étude
    étude's
    études
    

    follow

    Like tail -f, slice-file can stream updates after the initial slice.

    var sf = require('slice-file');
    var xs = sf('/var/mail/' + process.env.USER);
    xs.follow(-10).pipe(process.stdout);
    

    at first the previous 10 lines will render:

    $ node example/mail.js 
        id A2181740063; Fri, 12 Apr 2013 03:08:30 -0700 (PDT)
    Subject: beep boop
    To: <substack@beep>
    X-Mailer: mail (GNU Mailutils 2.2)
    Message-Id: <20130412100830.A2181740063@beep>
    Date: Fri, 12 Apr 2013 03:08:30 -0700 (PDT)
    From: substack@beep
    
    oh hello
    
    
    

    then if a message is sent:

    $ echo ahoy thar | mail -s 'oy' substack
    

    we see more data from the file:

    From substack@beep  Fri Apr 12 03:09:13 2013
    Return-Path: <substack@beep>
    X-Original-To: substack@beep
    Delivered-To: substack@beep
    Received: by beep (Postfix, from userid 1000)
        id 5E0C7740063; Fri, 12 Apr 2013 03:09:13 -0700 (PDT)
    Subject: oy
    To: <substack@beep>
    X-Mailer: mail (GNU Mailutils 2.2)
    Message-Id: <20130412100913.5E0C7740063@beep>
    Date: Fri, 12 Apr 2013 03:09:13 -0700 (PDT)
    From: substack@beep
    
    ahoy thar
    
    

    reverse

    You can also slice in reverse order, which is more efficient for negative-indexed slices because the lines don't need to be buffered:

    var sf = require('slice-file');
    var xs = sf('/usr/share/dict/words');
    xs.sliceReverse(-10).pipe(process.stdout);
    événements
    événement
    évolués
    évolué
    étuis
    étui's
    étui
    études
    étude's
    étude
    

    methods

    var sf = require('slice-file')

    var xs = sf(filename, opts={})

    Create a slice-file instance xs from a filename and some options opts.

    These opts are passed to fs.open():

    • opts.flags - string flags to open the file with, default "r"
    • opts.mode - mask to open the file with, default 0666

    If you already have a file descriptor open you can pass opts.fd to skip calling fs.open().

    Use opts.bufsize to set how much data to read in each chunk. Default 4096.

    var stream = xs.slice(i, j, cb)

    Return a readable stream that emits each line between line numbers [i,j) exactly like Array.prototype.slice(). Each line data buffer includes a trailing "\n" except for the last line if there is no trailing newline before the EOF.

    Just like Array.prototype.slice(), i and j may be negative.

    If cb(err, lines) is given, the lines will be buffered into lines.

    var stream = xs.sliceReverse(i, j, cb)

    Return a readable stream that emits each line between line numbers [i,j) just like .slice() but in reverse order. This is more efficient for negative-indexed slices because the lines don't need to be buffered.

    If cb(err, lines) is given, the lines will be buffered into lines.

    var stream = xs.follow(i, j)

    Return a readable stream of lines like xs.slice(), but instead of ending when the end of the file is reached, watch the file and stream new lines appended to the end of the file.

    This feature takes its name from tail -f.

    xs.close()

    Close the underlying file descriptor, stop any streams, and stop any file watchers.

    install

    With npm do:

    npm install slice-file
    

    license

    MIT

    Install

    npm i slice-file

    DownloadsWeekly Downloads

    113

    Version

    1.0.0

    License

    MIT

    Last publish

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