10 February 2010Seven essential WordPress plugins

Here are the plugins I recommend for use on a WordPress blog.

Most (not all) of these plugins are generic, meaning that they are not bound to a specific type of blog and may (or should) be used regardless of what you write.

All of these plugins are top quality (IMHO) and provide an invaluable service for any blogger. I wholeheartedly recommend that you use and support them. I think that all of these should be apart of a standard WordPress installation.
Read more…

Post a comment
Filed under: Security, Uncategorized
Tags: , , , , , , , , ,

9 February 2010@font-face for a programmer’s blog?

See Consolas in action

I’m sure that many of you are well aware of the exceptional @font-face CSS3 rule, which made life much easier for many designers, I would think. A few days ago I started wondering if it would be appropriate to use such an instrument on my blog… the site you’re on! Yoopie!

And, why not!? I love the idea of making my source codes more readable by using some custom font (Consolas anyone?). Anyway, I started looking around for some fonts and was not pleased with any of them (well to be fair I did like DejaVu Sans Mono but not as much as Consolas, unfortunately).
Read more…

Post a comment
Filed under: Graphics, Web-development
Tags: , , , , , ,

3 February 2010URI parsing using Bash built-in features

A bit of background

A while ago I posted an article describing how one could parse complete URIs in Bash using the sed program. Since then, I have realized that there is a better way to do it, a much better way: via Bash built-in pattern matching! 
Here are some benefits of this improvement:

  • It is no longer needed to execute an external program (i.e. sed) for the pattern matching. This translates to higher speed and lower memory and CPU usage, which means that you could use this parser to do much more intense URI parsing.
  • The new regular expressions are drastically simplified thanks to the ${BASH_REMATCH[*]} array that is able to hold more than 9 matched sub-expressions, unlike sed that can only work with single-digit escapes: \1-\9 (yuck!).
  • The parsing algorithm is contained in a single Bash function, so no external file is needed to hold the regular expressions. This also means, obviously, that the pattern file is no longer loaded from disk on every execution (so HDD is saved as well).
  • The generated variables are named identically to the first version, so you should be able to upgrade your scripts to this version with absolutely minimal effort.
  • [Edit]
    No eval instruction is needed (unlike in the first version), further improving performance.

Read more…

4 Comments
Filed under: Bash scripting, Command line tools
Tags: , , , , , ,

2 February 2010Quality Coding Practices

This is a set of guidelines that I put together starting a while back, which I try to respect when I write code. It is mostly (at least for now) oriented towards programming in C, but any systems programming language could benefit. Be aware that these do not apply to everyone or every scenario, adaptation and clever compromises are essential!

Now, this is obviously only a humble start, so I would like to ask the community (yes, you!) to pitch in and help grow (and correct) this list of useful principles, so that, in time, it may actually become something used by folks around the web to better their coding practices. C’mon, this will be fun, fun, fun! :D Read more…

Post a comment
Filed under: Projects, Tutorials
Tags: , , , , , , ,

2 February 2010First impressions on Loomiere/Stream performance

As promised, here are some of the first monitoring statistics of Loomiere/Stream in a production environment after moving away from psstream. Only one server is considered, a Quad-core Xeon with 8GB RAM (not that they are used anymore).

This shows the memory usage over one week (the switch was made on the 29th as is obvious).

Read more…

Post a comment
Filed under: Networking
Tags: , , , , , , , ,

30 January 2010Loomiere/Stream – A high performance streaming server

ATTENTION: Due to the fact that myself and my company are not yet satisfied with some issues regarding the legal terms of Loomiere/Stream, I think it is wise to take it (temporarily) offline until we resolve our concerns! Also some of the technical characteristics have been retracted.

Are you killing psstream?

Well, yes! I am sure that many of you already know about psstream (the PHP streaming extension I made a while back). Well, many things happened since then and I came to realize I could do better; a whole lot better actually. As of now the ‘psstream’ project is officially no longer developed (see below). It will remain on the website for some time to come for archiving purposes but that is it.

But wait, why did you do it?

For some time now I have be looking into improving the streaming mechanism for a large video-sharing project run by my company. PSStream was a first effort, and it did the job but soon ran into problems. None of our servers was able to properly stream more than 150 clients simultaneously and the resources were grossly wasted, hence, Loomiere/Stream. Read more…

4 Comments
Filed under: Networking, Projects
Tags: , , , , , , , , , , , , , , , ,

16 December 2009Recursive chmod with discrimination on files or directories

Version 3

An even better method is:

find "$target" -type f -exec chmod -c "$mode_files" {} \; \
      -or -type d -exec chmod -c "$mode_dir" {} \;

A true one-liner! :D

Version 2

A better method is this:

find "$target" -type f -exec chmod -c "$mode_files" {} \;
find "$target" -type d -exec chmod -c "$mode_dir" {} \;

This one can also be used from the command line.

Version 1

Many times I needed to apply certain permissions recursively on a given path but with different permissions on files than on directories (i.e. I want 0644 for files and 0744 for directories). This behaviour is not provided by the chmod tool so here is a simple and effective bash function to do just that:

# Recursively apply chmod to path.
# If mode_files is missing then apply mode_dir to files too.
# Params: target mode_dir [mode_files]
function deep_chmod() {
    function _walk() {
        local F
        for F in `find "$1"`; do
            local M="$3"; [[ `file -b "$F"` == "directory" ]] && M="$2"
            chmod -c "$M" "$F" > /dev/null
        done
    }
    if [[ $# > 2 ]]; then
        _walk "$1" "$2" "$3"
    else
        chmod -Rc "$2" "$1"
    fi
}

I’m looking for a way to improve on this since it is quite costly for large directories: for each file or directory at least two programs are executed (file and chmod) which is not very efficient! For now, it gets the job done.
Enjoy! :)

Post a comment
Filed under: Command line tools, One-liners
Tags: , , , ,

16 November 2009Bash URI parser using SED

Warning! This version is now obsolete!
Check out the new and improved version (using only Bash built-ins) here!

Here is a command-line (bash) script that uses sed to split the segments of an URI into usable variables. It also validates the given URI since malformed strings produce the text “ERROR” which can be handled accordingly:

# Assembling a sample URI (including an injection attack)
uri_1='http://user:pass@www.example.com:19741/dir1/dir2/file.php'
uri_2='?param=some_value&array[0]=123&param2=\`cat /etc/passwd\`'
uri_3='#bottom-left'
uri="$uri_1$uri_2$uri_3"

# Parse URI
op=`echo "$uri" | sed -nrf "uri.sed"`

# Handle invalid URI
[[ $op == 'ERROR' ]] && { echo "Invalid URI!"; exit 1; }

# Execute assignments
eval "$op"

# ...work with URI components...

Notice the "uri.sed" file given to sed?
Read more…

8 Comments
Filed under: Command line tools, Networking
Tags: , , , , , ,

6 November 2009Recursive file/directory change-detection

Version 2

Another, much faster method would be to use ls -lR to browse over the filesystem. On a newly installed Debian virtual machine (on Xen) hashing the entire filesystem (the root directory) took approximately 1.7 seconds. So, here it is:

ls -lR "$D" | sha1sum | sed 's/[ -]//g'

This method is sensitive to file name, size and modification size; usually that would be enough but if you need more control use…

Version 1

Detect when the contents of a file or directory ($D) changes:

find "$D" | while read f; do stat -t "$f"; done | sha1sum | sed 's/[ -]//g'

This yields a hash of the current state of the file or directory which is extremely sensitive to even the most subtle changes (even a simple touch to any file/directory somewhere inside “$D” changes the generated hash).

Read more…

4 Comments
Filed under: Command line tools, One-liners
Tags: , ,

6 November 2009Detect number of CPUs on a machine

Detect how many CPU cores are present on the running machine:

cat /proc/cpuinfo | grep -c processor

This can be very useful when writing multi-threaded programs to properly match the number of threads with the number of CPU cores.

Read more…

Post a comment
Filed under: Command line tools, One-liners
Tags: , , , , , ,