Jasny | Arnold's wor(l)ds

Linux desktop, PHP, Ubuntu

How to get a file extension

$ext = pathinfo($file_name, PATHINFO_EXTENSION);

my $ext = ($file_name =~ m/([^.]+)$/)[0];

ext = File.extname(file_name)

ext=${file_name##*.}
name=${file_name%.*}

import os
ext = os.path.splitext(file_name)[1]

31 May 2008 Arnold Daniels  

25 Responses to “How to get a file extension”

1. on 31 May 2008 at 22:20 1 Philip Olson

   It would be interesting to provide code with the following two examples:

   foo.tgz
   foo.tar.gz

   This would essentially require two snippets for each language… depending on what the user wanted to do.

2. on 31 May 2008 at 22:32 2 Jensen

   Python:
   import os
   ext = os.path.splitext(file_name)[1]

   If “file_name” is “my.file.txt” the “ext” variable will contain “.txt”.

3. on 31 May 2008 at 22:36 3 Arnold Daniels

   For .tar.gz, only gz is seen as the extension. If necessary, you need to make an exception for tar.gz.

   Also you might want to say that this it should only give an extension when the filename has a dot, eg README has no extension. This isn’t done correctly with the Perl and bash example.

   With a regex it would be

   /(?< =\.)(tar\.gz|[^./\/])$/

4. on 31 May 2008 at 23:03 4 Gareth Heyes

   Javascript:-

   /[^.]{1,3}$/.exec(’.testest.jpg’)

5. on 31 May 2008 at 23:04 5 Brutos

   Windows commandline:
   echo %~x1

6. on 31 May 2008 at 23:30 6 Bruce Weirdan

   @Gareth Heyes:
   extension is usually defined as last part after a dot (not limited to three characters). So it would be
   /[^.]+$/.exec(’filename.with.extension’) // here extension is ‘extension’

   @Arnold:
   Your comment form does not work with javascript off.

7. on 01 Jun 2008 at 02:09 7 Jeremy Privett

   C# –

   FileInfo f = new FileInfo(”test.txt”);
   string ext = f.Extension; # ext = txt

8. on 01 Jun 2008 at 04:05 8 Alan Knowles

   D
   char[] ext =std.path.getExt(fnam)

   gtkds (javascript)
   var ext= Path.getExt(fname)

9. on 01 Jun 2008 at 18:35 9 ace

   // what about writing classes/functions for common operations?

   $ext = File::ext($filename);

   // included file

   class File {
   static function ext($filename)
   {
   return pathinfo($file_name, PATHINFO_EXTENSION);
   }
   }

10. on 05 Jun 2008 at 10:26 10 gi_gio

    Hi Arnold, sorry if I’m posting here, but I did not found another way to contact you.
    I’ve just read a message that you posted on the forum of the mysql website.
    You wrote that you’ve got a php lib based on fast regexp that can parse a mysql query string to retrieve information like: operation (INSERT, UPDATE..), tables, fields… and so on.
    I was looking for such a library, can you help me, please?

    Thank you in advance!

11. on 10 Jun 2008 at 04:54 11 rx8wej

    in C# (alternative):

    string path = “C:\file.txt”;
    string ext = path.SubString(path.LastIndexOf(”.”) + 1);

12. on 26 Jun 2008 at 22:27 12 Henk

    @ ace for his ‘making it a class’ business, in a proper OO thingy, you’d more likely see a structure like

    $file = new File(’somefile.txt’);
    echo $file->GetExtension();

    since ‘putting it into a class’, as described by you, is basically just ‘wrapping the php function into another function, with the additional overhead of putting it into a class in order to simulate namespaces’.

13. on 21 Dec 2008 at 16:08 13 private credit record score in calgary alberta

    private credit record score in calgary alberta…

    redouble?missed,leafed!hatred,…

14. on 30 Dec 2008 at 23:40 14 diyopatino

    my ($ext) = $file_name =~ m/([^.]+$)/;

15. on 28 Feb 2009 at 18:03 15 Maelvon

    In a CGI with perl, I got the extension with:

    my $ext = ($file_name =~ m/.*\.(.+)$/)[0];

16. on 19 Jun 2009 at 05:47 16 Muhammad Azhar

    Thanks for ur kind help.

17. on 30 Sep 2009 at 16:18 17 NoMoreFreeBeer_Ban_Inbev_AnheuserBusch

    PHP
    Keep it simple!
    Use explode!

    $extension = end(explode(’.', $file));

    Returns everything after the last “.”.

18. on 30 Sep 2009 at 16:46 18 Arnold Daniels

    Using explode won’t give you the wanted result:

    $file = “/etc/passwd”;
    $extension = end(explode(’.’, $file));
    echo $extension; // Outputs ‘/etc/passwd’

    For PHP use pathinfo() as described in the above article.

19. on 30 Sep 2009 at 20:28 19 Sandor

    end(explode works quite well as posted. Without the “end” you will get the undesired result mentioned above.

    Here is some info on explode and also has an example of the end(explode method that shows that it does work quite well.

    http://us3.php.net/manual/en/function.explode.php#87049

    My expertise quite limited. Been writing in php off and on only about 5 years now. The explode method works for me though in many ways.

    The goal was to return the extension of a file name. Just like the examples at the top of the page here. Right?

    That explode example will do just that. I use it all the time in my snippets. Efficiency is relative to the end app I guess though.

    $file = “someimage.jpg”; //or even some.image.jpg

    $extension = end(explode(’.', $file));

    outputs jpg

    // It does everything after the last ‘.’

    I was told by many it is the most efficient way to grab a file name extension with php. If there is a way that uses less resources, I will use it instead.

    Using pathinfo:

    $path_parts = pathinfo(’/www/index.html’);

    Enables me to:

    echo $path_parts['dirname'], “\n”;
    echo $path_parts['basename'], “\n”;
    echo $path_parts['extension'], “\n”;
    echo $path_parts['filename'], “\n”;

    I “think” pathinfo uses more “resources” than just getting the specific result as I did in the explode example. I could be very wrong. If someone could prove one is method “better” that the other, I will use the better one for sure! I also become concerned about security. The explode method exposes more by far. But it is php.

    Now, in cases where you need to break a file name up, do some pattern matching or directory creation then reconstruct it all later for some reason or another, pathinfo has everything you need all ready and waiting. I use it for that frequently. But, when I don’t, I use the explode method to grab parts of a string or file. When I actually write apps in php that is..

    Great topic. So many ways to perform a seemingly simple task. But, just because it is simple does not mean it is easy!

    Thanks guys!

20. on 01 Oct 2009 at 11:39 20 Arnold Daniels

    Sandor: Thanks for you input, but please have a closer look at my comment.

    Using explode will not work correctly if the file does not have an extension. It will work for ‘/var/www/someimage.jpg’, but not for ‘/etc/group’. Please execute the code and see for your self.

    Please also note the PATHINFO_% constants. You don’t need to get the whole array and than get the extension part from that.

    This is most definitely faster than doing an explode + end, since you don’t need to create an array, which is a relative expensive operation.

    define('LOOP', 10000);
     
    function wasteTime() {
        for ($i=0; $i<LOOP; $i++);
    }
     
    function usePathinfo() {
    	for ($i=0; $i<LOOP; $i++) pathinfo("/var/www/image.jpg", PATHINFO_EXTENSION);
    }
     
    function useExplode() {
    	for ($i=0; $i<LOOP; $i++) end(explode('.', "/var/www/image.jpg"));
    }
     
    wasteTime();
    usePathinfo();
    useExplode();

    

    I made a error in the benchmark code. Updated the profiling results

21. on 01 Oct 2009 at 13:50 21 Sandor

    Excellent, thank you… Your input here forces me to test all my snippets in Zend studio. What’s the use of having it if I don’t use it!

    As far as the security holes when no extension is present (and other possibilities), I was sanitizing before I got to explode. Chalking up some more time on to the explode method.

    Thanks again!

22. on 01 Oct 2009 at 14:34 22 Sandor

    So in PERL, would using

    $string= do some /stuff $ENV(’PATH_INFO’)/g;

    be a better/safer way to grab an extension or even a whole ?query. Replacing the need for a query and even avoiding loading a perl module like CGI. Hence more security and a so on like:

    #!/usr/bin/perl -Tw
    use strict;
    use warnings;
    BEGIN{$SIG{__DIE__} = \&FatalErr} #my dies go to a sub#
    $ENV{PATH} = “bin:/usr/bin”;
    delete ($ENV{qw(IFS CDPATH BASH_ENV ENV)});
    my $string=”";
    $string= do some /stuff with $ENV(’PATH_INFO’) /here/;
    #sanitize $string here
    #split it up as needed..

    All vars are now ready…

    Prob a one liner that can break up the whole deal after taint.

    That was just a quick type so, don’t take it literally, just a concept.

    I have a PERL sub I am working on that I would like to share here for help in developing it. Everyone who serves up images could use it when done. I will find the proper category to post it here when I clean it up a bit..

23. on 04 Dec 2009 at 23:02 23 Cully Larson

    For Perl, you forgot the parens around your match group:

    my $ext = ($file_name =~ m/([^.]+)$/)[0];

24. on 21 Dec 2009 at 10:20 24 satan

    Thanks! This helped a lot!!

25. on 18 Feb 2010 at 23:33 25 Nathan L Smith

    CommonJS:

    From http://wiki.commonjs.org/wiki/Filesystem/A, works on Narwhal:

    require(”file”).extension(fileName);

Leave a Reply

Name (required)

Mail (hidden) (required)

Website