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660
Alec Smart

Is there something similar to @import in CSS in JavaScript that allows you to include a JavaScript file inside a JavaScript file?

Answered By: e-satis ( 727)

There is no import / include / require in javascript, but there are two main ways to achieve what you want:

1 - You can load it with an AJAX call then use eval.

This is the most straightforward way but it's limited to your domain because of the Javascript safety settings, and using eval is opening the door to bugs and hacks.

2 - Add a script tag with the script URL in the HTML.

Definitely the best way to go. You can load the script even from a foreign server, and it's clean as you use the browser parser to evaluate the code. You can put the <script /> tag in the head of the web page, or at the bottom of the body.

Both of these solutions are discussed and illustrated here.

Now, there is a big issue you must know about. Doing that implies that you remotely load the code. Modern web browsers will load the file and keep executing your current script because they load everything asynchronously to improve performances.

It means that if you use these tricks directly, you won't be able to use your newly loaded code the next line after you asked it to be loaded, because it will be still loading.

E.G : my_lovely_script.js contains MySuperObject

var js = document.createElement("script");

js.type = "text/javascript";
js.src = jsFilePath;

document.body.appendChild(js);

var s = new MySuperObject();

Error : MySuperObject is undefined

Then you reload the page hitting F5. And it works! Confusing...

So what to do about it ?

Well, you can use the hack the author suggests in the link I gave you. In summary, for people in a hurry, he uses en event to run a callback function when the script is loaded. So you can put all the code using the remote library in the callback function. E.G :

function loadScript(url, callback)
{
    // adding the script tag to the head as suggested before
   var head = document.getElementsByTagName('head')[0];
   var script = document.createElement('script');
   script.type = 'text/javascript';
   script.src = url;

   // then bind the event to the callback function 
   // there are several events for cross browser compatibility
   script.onreadystatechange = callback;
   script.onload = callback;

   // fire the loading
   head.appendChild(script);
}

Then you write the code you want to use AFTER the script is loaded in a lambda function :

var myPrettyCode = function() {

   // here, do what ever you want

};

Then you run all that :

loadScript("my_lovely_script.js", myPrettyCode);

Ok, I got it. But it's a pain to write all this stuff.

Well, in that case, you can use as always the fantastic free jQuery framework, which let you do the very same thing in one line :

$.getScript("my_lovely_script.js", function(){


   alert("Script loaded and executed.");
   // here you can use anything you defined in the loaded script

});
536
avdgaag

Say I'm in a Git repository. I delete a file and commit that change. I continue working and make some more commits. Then, I find I need to restore that file.

I know I can checkout a file using git checkout HEAD^ foo.bar, but I don't really know when that file was deleted.

  1. What would be the quickest way to find the commit that deleted a given filename?
  2. What would be the easiest way to get that file back into my working copy?

I'm hoping I don't have to manually browse my logs, checkout the entire project for a given SHA and then manually copy that file into my original project checkout.

Answered By: Charles Bailey ( 652)

Find the last commit that affected the given path. As the file isn't in the HEAD commit, this commit must have deleted it.

git rev-list -n 1 HEAD -- <file_path>

Then checkout the version at the commit before.

git checkout <deleting_commit>^ -- <file_path>

Or in one command, if $file is the file in question.

git checkout $(git rev-list -n 1 HEAD -- "$file")^ -- "$file"
521
spence91

How do I check if a file exists, using Python, without using a try: statement?

Answered By: Brian ( 518)

Just to add to the answers - it's usually safer to use the following approach:

try:
   with open('filename'): pass
except IOError:
   print 'Oh dear.'

os.path.exists() only tells you that the file existed at that point. In the tiny interval between that and running code that depends on it, it is possible that someone will have created or deleted the file.

This is a race condition that can often lead to security vulnerabilities. An attacker can create a symlink to an arbitrary file immediately after the program checks no file exists. This way arbitrary files can be read or overwritten with the privilege level your program runs with.

172
Pete

It has always bothered me that the only way to copy a file in Java involves opening streams, declaring a buffer, reading in one file, looping through it, and writing it out to the other steam. The web is littered with similar, yet still slightly different implementations of this type of solution.

Is there a better way that stays within the bounds of the Java language (meaning does not involve exec-ing OS specific commands)? Perhaps in some reliable open source utility package, that would at least obscure this underlying implementation and provide a one line solution?

Answered By: delfuego ( 133)

As toolkit mentions above, Apache Commons IO is the way to go, specifically FileUtils.copyFile(); it handles all the heavy lifting for you.

And as a postscript, note that recent versions of FileUtils (such as the 2.0.1 release) have added the use of NIO for copying files; NIO can significantly increase file-copying performance, in a large part because the NIO routines defer copying directly to the OS/filesystem rather than handle it by reading and writing bytes through the Java layer. So if you're looking for performance, it might be worth checking that you are using a recent version of FileUtils.

171
jodonnell

By default, Eclipse won't show my .htaccess file that I maintain in my project. It just shows an empty folder in the Package Viewer tree. How can I get it to show up? No obvious preferences.

Answered By: scubabbl ( 289)

In the package explorer, in the upper right corner of the view, there is a little down arrow. Tool tip will say view menu.

Click that, Select Filters. uncheck .* resources.

So Package Explorer -> View Menu -> Filters -> uncheck .* resources.

143
Mark Biek

I have a script that needs to do some stuff based on file creation & modification dates but has to run on Linux & Windows.

What's the best cross-platform way to get file creation & modification date/times in Python?

Answered By: Bryan Oakley ( 152)

You have a couple of choices. For one, you can use the os.path.getmtime and os.path.getctime functions:

import os.path, time
print "last modified: %s" % time.ctime(os.path.getmtime(file))
print "created: %s" % time.ctime(os.path.getctime(file))

Your other option is to use os.stat:

import os, time
(mode, ino, dev, nlink, uid, gid, size, atime, mtime, ctime) = os.stat(file)
print "last modified: %s" % time.ctime(mtime)

Note: ctime() does not refer to creation time on *nix systems, but rather the last time the inode data changed. (thanks to kojiro for making that fact more clear in the comments by providing a link to an interesting blog post)