Werx Limited » software development

node.js at Facebook

wes — Mon, 23 Jan 2012 14:18:24 +0000

No related content found.

Simple init.d script template

wes — Thu, 05 Jan 2012 19:25:24 +0000

Recently I found the need to create an init.d script and since I had a hard time finding an example elsewhere¹, here’s the overly simple script I came up with to get the job done:

#!/bin/bash
# myapp daemon
# chkconfig: 345 20 80
# description: myapp daemon
# processname: myapp

DAEMON_PATH="/home/wes/Development/projects/myapp"

DAEMON=myapp
DAEMONOPTS="-my opts"

NAME=myapp
DESC="My daemon description"
PIDFILE=/var/run/$NAME.pid
SCRIPTNAME=/etc/init.d/$NAME

case "$1" in
start)
	printf "%-50s" "Starting $NAME..."
	cd $DAEMON_PATH
	PID=`$DAEMON $DAEMONOPTS > /dev/null 2>&1 & echo $!`
	#echo "Saving PID" $PID " to " $PIDFILE
        if [ -z $PID ]; then
            printf "%s\n" "Fail"
        else
            echo $PID > $PIDFILE
            printf "%s\n" "Ok"
        fi
;;
status)
        printf "%-50s" "Checking $NAME..."
        if [ -f $PIDFILE ]; then
            PID=`cat $PIDFILE`
            if [ -z `ps axf | grep 5003 | grep -v grep` ]; then
                printf "%s\n" "Process dead but pidfile exists"
            else
                echo "Running"
            fi
        else
            printf "%s\n" "Service not running"
        fi
;;
stop)
        printf "%-50s" "Stopping $NAME"
            PID=`cat $PIDFILE`
            cd $DAEMON_PATH
        if [ -f $PIDFILE ]; then
            kill -HUP $PID
            printf "%s\n" "Ok"
            rm -rf $PIDFILE
        else
            printf "%s\n" "pidfile not found"
        fi
;;

restart)
  	$0 stop
  	$0 start
;;

*)
        echo "Usage: $0 {status|start|stop|restart}"
        exit 1
esac

This script will work in /etc/init.d on Xubuntu 11.10 (so most Debian-based systems) and CentOS 5.5 and you can control it via chkconfig.

No related content found.

That said, if you know of such an example I’d love to hear from you.

Share/Save

Fun with jsonselect

wes — Wed, 16 Nov 2011 16:39:07 +0000

One of the strengths of CSS and jQuery is that it provides a common and powerful mechanism known as a selector language for referencing bits of data, especially data whose structure is not exactly known at runtime which makes such an addressing scheme a perfect fit for the often lumpy world of HTML.

Increasingly JSON is being used as a transport medium for data and with the rise of NoSQL solutions, having a selector language for JSON makes a lot of sense when dealing with JSON documents whose structure isn’t deterministic.

JSONSelect provides a good implementation of just such a JSON selector language but after working with it on a project I found myself needing to do more than it allowed me to do. Namely, I wanted 1. to be able to perform a selection and receive matching paths instead of the data contained in those paths and I wanted 2. to be able to modify data specified at a path location in-place.

jsonselect.match(sel, obj, asPath); // Added the asPath flag to return a path instead of the values
jsonselect.forEach(sel, obj, fun, asPath); // Added the same flag to forEach, I use this to
jsonselect.get(path,obj); // For getting the value using a path
jsonselect.set(path, value, obj); // For setting the value of a path
jsonselect.del(path,root); // For deleting a path

Here is my modified version of jsonselect in case anyone needs help solving the same problems I mentioned above.

No related content found.

Share/Save

Finding yesterday’s beginning and ending unix timestamp

wes — Thu, 25 Aug 2011 20:03:58 +0000

When writing reports I’ve often come across the need to find the unix timestamp beginning and end of a day. Here is a Python snippet that does just that.

yesterday = datetime.datetime.now() - datetime.timedelta(days = 1)
yesterday_beginning = datetime.datetime(yesterday.year, yesterday.month, yesterday.day,0,0,0,0)
yesterday_beginning_time = int(time.mktime(yesterday_beginning.timetuple()))
yesterday_end = datetime.datetime(yesterday.year, yesterday.month, yesterday.day,23,59,59,999)
yesterday_end_time = int(time.mktime(yesterday_end.timetuple()))

print yesterday_beginning_time
print yesterday_end_time

No related content found.

Share/Save

Check an array for all null values

wes — Mon, 13 Jun 2011 20:38:00 +0000

Here is a simple function to check an array to see if it contains all null values.

function allNulls($arr) {
    if(is_array($arr) && count(array_diff($arr, array(null))) == 0) {
            return true;
    }

    return false;
}

echo (allNulls(array(null,null,null)) ? "true" : "false") . PHP_EOL;
echo (allNulls(array(null,1,null)) ? "true" : "false") . PHP_EOL;
echo (allNulls(array("test",null,null)) ? "true" : "false") . PHP_EOL;
echo (allNulls(array("",null,null)) ? "true" : "false") . PHP_EOL;
echo (allNulls(array(0,null,null)) ? "true" : "false") . PHP_EOL;

No related content found.

Share/Save

Simple PHP Proxy

wes — Tue, 24 May 2011 12:00:17 +0000

While developing apps that use external web services, a proxy often comes in handy in order to bypass the pesky XSS security settings found in most browsers. Here is a simple PHP proxy I’ve found quite helpful.

No related content found.

Share/Save

Dividing a file into chunks along line endings in Erlang

wes — Mon, 23 May 2011 12:26:38 +0000

I’ve been dabbling in Erlang recently. I’ve wanted to learn a functional programming language for a while now and Erlang’s concurrency make it rather attractive.

For my “hello world” app, I decided to write a simple log parser which processes chunks of a file in parallel. Here is a part of that app which produces a list of tuples which describes the chunks adjusted to the nearest newline (Unix newlines, \n, in this case).

getChunkDivisions(File, 0, Chunksize, ChunkDivisions) ->
	[{chunk,0,Chunksize}|ChunkDivisions];
getChunkDivisions(File, Size, Chunksize, ChunkDivisions) ->
	if
		Size-Chunksize=<0 ->
			ComputedChunkEnd = Chunksize-(Chunksize-Size),
			CorrectedChunkEnd = walkToNextLineBreak(File, ComputedChunkEnd),
			getChunkDivisions(File, 0, CorrectedChunkEnd, ChunkDivisions);
		true		 ->
			ComputedChunkEnd = Size-Chunksize,
			CorrectedChunkEnd = walkToNextLineBreak(File, ComputedChunkEnd),
			getChunkDivisions(File, CorrectedChunkEnd, Chunksize, [{chunk,CorrectedChunkEnd,Size}|ChunkDivisions])
	end.

walkToNextLineBreak(File,Start) ->
	file:position(File, Start-1),
	{ok, Data} = file:read(File, 1024),
	Start+string:chr(Data, $\n).

No related content found.

Share/Save

A Java String permutations utility

wes — Tue, 10 May 2011 03:21:31 +0000

On a recent project I need to find all the possible permutations of a given URL. Stripping off subdomains, paths, and query parameters. Here is the first part of the solution. A method which takes a string and strips it down based on a given divider in a given direction at a given interval.

Here’s the code:

private static String[] getPermutations(String whole, String divider, int lim, int dir) {
	   String[] chunks = whole.split((divider.matches("\\.") ? "\\" : "")+divider);
	   System.out.println("chunks.length: "+chunks.length);

	   if(chunks.length <= lim) {
		   System.out.println("return whole: "+whole);
		   return new String[]{whole};
	   }

	   String[] permutations = new String[chunks.length-lim];

	   if(dir == 1) {
		   	permutations[0] = whole;
   		    System.out.println("permutations[0]: "+permutations[0]);
			for(int i = 1; i < chunks.length-lim; i++) {
			   String permutation = "";
			   for(int o = i; o < chunks.length; o++) {
				   permutation += (o == i ? "" : divider) + chunks[o];
			   }
			   permutations[i] = permutation;
			   System.out.println("permutations["+i+"]: "+permutations[i]);
			}
	   } else if(dir == -1) {
		   for(int i = 0; i < chunks.length-lim; i++) {
			   String permutation = "";
	 		   for(int o = 0; o < chunks.length-i; o++) {
				   permutation += (o == 0 ? "" : divider) + chunks[o];
			   }
			   permutations[i] = permutation;
			   System.out.println("permutations["+i+"]: "+permutations[i]);
			}
	   }

	   return permutations;
   }

Here is an example of it being used.

Input:

      getPermutations("com",".",1, 1);
      getPermutations("google.com",".",1, 1);
      getPermutations("a.b.c.d.e.cool.google.com",".",1, 1);
      getPermutations("/path/asdf/a/b/c/d/e/f","/",0, -1);
      getPermutations("a=b&c=d&e=f","&",0, -1);

Output:

$ javac Runme.java && java Runme
chunks.length: 1
return whole: com
chunks.length: 2
permutations[0]: google.com
chunks.length: 8
permutations[0]: a.b.c.d.e.cool.google.com
permutations[1]: b.c.d.e.cool.google.com
permutations[2]: c.d.e.cool.google.com
permutations[3]: d.e.cool.google.com
permutations[4]: e.cool.google.com
permutations[5]: cool.google.com
permutations[6]: google.com
chunks.length: 9
permutations[0]: /path/asdf/a/b/c/d/e/f
permutations[1]: /path/asdf/a/b/c/d/e
permutations[2]: /path/asdf/a/b/c/d
permutations[3]: /path/asdf/a/b/c
permutations[4]: /path/asdf/a/b
permutations[5]: /path/asdf/a
permutations[6]: /path/asdf
permutations[7]: /path
permutations[8]:
chunks.length: 3
permutations[0]: a=b&c=d&e=f
permutations[1]: a=b&c=d
permutations[2]: a=b

Next I'll need to combine the URL components to get a list of valid URLs..

No related content found.

Share/Save

Javascript color gradient calculator

wes — Mon, 02 May 2011 15:00:18 +0000

Here is a color calculator I adapted from a friend’s PHP implementation:

Color = function() {
};

Color.hexdec = function(hex_string) {
    hex_string = (hex_string + '').replace(/[^a-f0-9]/gi, '');
    return parseInt(hex_string, 16);
}

Color.dechex = function(number) {
    if (number < 0) {
        number = 0xFFFFFFFF + number + 1;
    }
    return parseInt(number, 10).toString(16);
}

Color.pad = function(number, length) {
    var str = '' + number;
    while (str.length < length) {
        str = '0' + str;
    }
    return str;
}

Color.calcgrad = function(val, color1, color2) {

    if(!color1.match(/^#[0-9a-f]{6}/) || !color2.match(/^#[0-9a-f]{6}/)) return 'match err!';

    if (val > 1) {
        val = 1;
    }
    if (val < 0) {
        val = 0;
    }
    val = parseFloat(val);

    c1 = [Color.hexdec(color1.substr(1,2)), Color.hexdec(color1.substr(3,2)), Color.hexdec(color1.substr(5,2))]; //b
    c2 = [Color.hexdec(color2.substr(1,2)), Color.hexdec(color2.substr(3,2)), Color.hexdec(color2.substr(5,2))]; //r

    if (val < .5) {
        delta = [(c2[0] - c1[0]), (c2[1] - c1[1]), (c1[2] - c2[2])];
        arrColor = [c1[0] +¹ * 2), c1[1] -² * 2), c1[2] -³ * 2)];
    }
    return '#'+Color.pad(Color.dechex(arrColor[0]),2)+Color.pad(Color.dechex(arrColor[1]),2)+Color.pad(Color.dechex(arrColor[2]),2);
}

No related content found.

delta[0] * val) * 2), c1[1] + ((delta[1] * val) * 2), c1[2] - ((delta[2] * val) * 2)]; } else { delta = [(c1[0] - c2[0]), (c1[1] - c2[1]), (c1[2] - c2[2])]; arrColor = [c1[0] - ((delta[0] * (val - .5
delta[1] * (val - .5
delta[2] * (val - .5

Werx Limited » software development

node.js at Facebook

Simple init.d script template

Fun with jsonselect

Finding yesterday’s beginning and ending unix timestamp

Check an array for all null values

Simple PHP Proxy

Dividing a file into chunks along line endings in Erlang

A Java String permutations utility

Javascript color gradient calculator

Dan Cathy: High Tech for High Customer Touch