How to replace tabs by spaces in whole codebase?

I’ve stared working on a project on github, written in php, that have mixed spaces and tabs for indent, I’m using GNU/Linux so I thought that I just replace all tabs by spaces using bash. Here is the command I’ve used that just did that:

find . -type f -name '*.php' | while read file; do
     grep $'\t' $file > /dev/null && sed -ie 's/\t/    /g' $file


  • find . -type f -name '*.php' – this will search for all files with php extension, in current directory. I’ve used -type f to return only files since there where directories that end with php.
  • while read file; do ... done – while loop over files found by find, the filename will be in file variable
  • grep $'\t' $file > /dev/null – this will return true if file contain tabs
  • & & execute next command if previous is true
  • sed -ie 's/\t/ /g' $file – replace tabs by spaces in file inline (-i option)

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Get list of github contributors in node.js

Recently I needed to send emails to all contributors to my github project, so I wrote a little script in node.js (actually my first try was ruby, but have problems with https). Here is the script using only native modules:


var https = require('https');
var path = require('path');
function get(host, path, callback) {
    var options = {
        host: host,
        path: path,
        headers: {
            'User-Agent': 'Node.js' //required by github api
    https.get(options, function(res) {
        var output = '';

        res.on('data', function (chunk) {
            output += chunk;

        res.on('end', function() {

if (process.argv.length == 4) {
    var user = process.argv[2];
    var repo = process.argv[3];
    var path = '/repos/' + user + '/' + repo + '/contributors'
    get('', path, function(contributors) {
        contributors.forEach(function(contributor) {
            if (contributor.login != user) {
                var path = contributor.url.replace(/https:\/\/[^\/]+/, '');
                get('', path, function(user) {
                    if ( {
                        var email = ? ' <' + + '>' : ''; 
                        console.log( + email);
} else {
    console.log('usage: \n' + path.basename(process.argv[1]) + ' user repo');

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Reading GET, POST and Cookie values in guile scheme

I’ve start playing with cgi in guile scheme and I came up with the functions to read GET, POST and Cookie values that I want to share. here is the code:

(use-modules (web uri)) ;; includes uri-decode procedure

(define (read-port port)
    (let iter ((result '()) (chr (read-char port)))
        (if (eof-object? chr)
            (list->string result)
            (iter (append result (list chr)) (read-char port)))))

(define (params->alist string fn sep)
  (map (lambda (pair)
          (let* ((list (string-split pair #\=))
                 (key (fn (string-trim (car list))))
                 (value (fn (string-trim (string-join (cdr list) "=")))))
             (cons key value)))
       (string-split string sep)))

(define (create-param-proc string fn sep)
   (if (or (equal? string #f) (equal? string ""))
       (lambda (var) "")
       (let ((query (params->alist string fn sep)))
          (lambda (var)
             (let ((pair (assoc var query)))
               (if (null? pair)
                   (cdr pair)))))))

(define GET (create-param-proc (getenv "QUERY_STRING") uri-decode #\&))
(define POST (create-param-proc (read-port (current-input-port)) uri-decode #\&))
(define COOKIE (create-param-proc (getenv "HTTP_COOKIE") identity #\;))

And to get the values you just execute one of GET, POST, COOKIE procedures:

(display (string-append "foo: " (GET "foo")))

(display (string-append "foo: " (POST "foo")))
(display (string-append "foo: " (COOKIE "foo")))

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Async shell command execution in GNU Emacs

In GNU Emacs if you execute shell command for instance using exec function the whole Editor freeze until shell command is finished. So I’ve written asynchronous version of exec:

(defun async-exec-command (command &rest success)
  (interactive "MExecute command: ")
  (let* ((buffer-name (generate-new-buffer-name "**shell**"))
         (buffer (get-buffer-create buffer-name))
         (process (apply #'start-process
                         (append (list buffer-name buffer)
                                 (split-string command " ")))))
    (lexical-let ((buffer buffer) (success (car success)) (command command))
      (set-process-sentinel process
                            (if success
                                (lambda (process str)
                                    (set-buffer buffer)
                                    (let ((content (buffer-string)))
                                      (kill-buffer buffer)
                                      (if (or (string= str "finished\n")
                                              (string-match "exited abnormally" str))
                                          (funcall success content)
                                        (message content)))))
                              (lambda (proces str)
                                (kill-buffer buffer)))))
    (concat "execute: " command)))

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How to backup 8GB file or larger on fat32 from linux

I have external USB hard drive that use Fat32 (so I can use it on windows machine as well on GNU/Linux). I needed to reinstall my OS (Xubuntu) and repartition the disk, so I need to copy all my files to external drive. But I’ve got 15GB virtualbox file.

On GNU/Linux or MacOS X you can use standard tools to split the file and then merge it back.

Here is a code that will compress and create 4GB chunks.

tar czvf file.tar.gz directory/
split -b $(echo "4*(2^30)-1" | bc) --verbose file.tar.gz file.tar.gz-

it will create files like file.tar.gz-aa file.tar.gz-ab that can be copy to Fat32 partition because they are smaller then 4GB (2^30 is 1GB in bytes).

to merge those files together you can just cat them

cat file.tar.gz-aa file.tar.gz-ab > file.tar.gz

if you want to see progress bar you can use pv command. This is the smallest way I came up with to do this:

cat file.tar.gz-aa file.tar.gz-ab | pv -s $(ls -l file.tar.gz-aa file.tar.gz-ab | cut -d' ' -f5 | tr '\n' '+' | sed -e 's/+$//' -e 's/.*/echo -n $(( & ))/' | bash) > file.tar.gz

Here is a function that can be put into .bashrc file

function cat-pv () {
    cat $@ | pv -s $(ls -l $@ | cut -d' ' -f5 | tr '\n' '+' | sed -e 's/+$//' -e 's/.*/echo -n $(( & ))/' | bash)

Here I found shorter way to calculate size of list of files it use awk:

ls -lrt | awk '{ total += $5 }; END { print total }'

So the function can be strink to

function cat-pv () {
     cat $@ | pv -s $(ls -lrt $@ | awk '{ total += $5 }; END { print total }')

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Cross-Domain LocalStorage

As you may know, LocalStorage is domain based. You can’t read or write from localstorage that’s on different domain, even if that’s subdomain. But there is iframe trick that you can use to store data from domain to it’s subdomain.

Basically you create an iframe that’s hosted on your other domain, then you send PostMessage to that iframe and inside iframe you set that value of localStorage.
Here is the code:


window.onmessage = function(e) {
  if (e.origin !== "") {
  var payload = JSON.parse(;
  localStorage.setItem(payload.key, JSON.stringify(;

main file

window.onload = function() {
    var win = document.getElementsByTagName('iframe')[0].contentWindow;
    var obj = {
       name: "Jack"
    win.postMessage(JSON.stringify({key: 'storage', data: obj}), "*");

<a href=""></a>

If you want to save and load value from LocalStorage, you can PostMessage with method key that will indicate what action it need to take. You can also send message back from iframe to it’s parent with data read from localStorage.


document.domain = "";
window.onmessage = function(e) {
    if (e.origin !== "") {
    var payload = JSON.parse(;
    switch(payload.method) {
        case 'set':
            localStorage.setItem(payload.key, JSON.stringify(;
        case 'get':
            var parent = window.parent;
            var data = localStorage.getItem(payload.key);
            parent.postMessage(data, "*");
        case 'remove':

Your main page on

window.onload = function() {
    var iframe = document.getElementsByTagName('iframe')[0];
    var win;
    // some browser (don't remember which one) throw exception when you try to access
    // contentWindow for the first time, it work when you do that second time
    try {
        win = iframe.contentWindow;
    } catch(e) {
        win = iframe.contentWindow;
    var obj = {
       name: "Jack"
    // save obj in subdomain localStorage
    win.postMessage(JSON.stringify({key: 'storage', method: "set", data: obj}), "*");
    window.onmessage = function(e) {
        if (e.origin != "") {
        // this will log "Jack"
    // load previously saved data
    win.postMessage(JSON.stringify({key: 'storage', method: "get"}), "*");

Here is a demo that use my sysend library to send messages to other tab in same browser (the library use localStorage for this). It use iframe proxy to send message from to and vice versa. Iframe is hosted on both domains.

The only caveat is that in Firefox, it seems that you need to enable CORS on Iframe. If you use apache server you can enable it in .htaccess file with this code:

Header set Access-Control-Allow-Origin "*"
Header set Access-Control-Allow-Methods: "GET"

it will enable CORS for all files, if you want to enable CORS for a single file, this should work:

<Files "iframe.html">
  Header set Access-Control-Allow-Origin "*"
  Header set Access-Control-Allow-Methods: "GET"

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40 JavaScript libraries you may not know about

Here is a list of useful libraries I had in my bookmarks, libraries that I need to use in some of my future projects.

  • Drawing and animation
  • Language extensions
  • Utilites
    • URI.js – library for handling urls
    • rangy – Text range library
    • color-thief – pick color(s) from image
    • stacktrace.js – get the stacktrace
    • XRegExp – extended regular expressions
    • -prefix-free – CSS3 without prefixes
    • mathjs – An extensive math library for JavaScript and Node.js
    • numeraljs – library for formatting and manipulating numbers
    • String.js – string manipulation library
    • Ocrad.js – Optical Character Recognition in Javascript
    • filer.js – wrapper over HTML5 File API
  • DOM
  • Events
    • jwerty – keyboard events
    • jquery-simulate – simulate keyboard and mouse events
    • Mousetrap – keyboard shortcuts
    • jQuery hashchange – hashchange event
    • jquery-waypoints – Execute a function when you sroll to the element
    • Steady.js – A jank-free module to do logic on the onscroll event without performance regressions in a @media-query like conditions.
    • sysend.js – Send messages between open pages in the browser (this one is actually my own)


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