Andrew Beaton :: FAQ » Programming

Grep to find ^M (Windows carriage return)

Andrew — Wed, 13 Jul 2011 16:58:17 +0000

There are two options here, one we used before when searching for the ^M’s in VI, the other is new:

^M

$'\r'

So to find all files with the Windows carriage return in them, use one of the following…

grep -r "^M" *

grep -r $'\r' *

^M is entered by pressing Ctrl+V followed by Ctrl+M

View output of the dd command

Andrew — Thu, 23 Jun 2011 10:48:36 +0000

Recently whilst wiping some old hard disks I thought it would be useful to see what the ‘dd’ command was doing, rather than sitting there blankly for hour. I knocked up a little bash script to run in another terminal that will update the terminal running dd with some useful status information.

In this example, dd will be run as…

$ dd if=/dev/random of=/dev/sda

copy the following into ddUpdate.sh for example and run it…

#!/bin/sh ddpid=`ps auwx | awk '/dd if/ && !/awk/ { print $2}'` while [ "$ddpid" != "" ] do kill -USR1 $ddpid sleep 1 ddpid=`ps auwx | awk '/dd if/ && !/awk/ { print $2}'` done

This outputs the following to the terminal running dd…

xxxxxx records in xxxxxx records out xxxxxx bytes (xx nn) copied, xxxx s, xx MB/s

Get DateTime in YYYY-mm-dd HH:MM:SS format using Perl

Andrew — Thu, 14 Apr 2011 11:54:34 +0000

For many years I’ve been using the long process of obtaining everything from localtime(), adding 1900 to the year etc. etc. but I’ve just come across the method below, which uses strftime from the POSIX module.

use POSIX; my $DateTime = strftime "%F %T", localtime $^T;

This gives you:

2006-10-02 02:06:07

Now that’s a lot easier!

“Object reference not set to an instance of an object.” when using OpenSubKey

Andrew — Tue, 09 Nov 2010 20:17:37 +0000

Whilst using a working project on my new development machine, I came across an issue that stumped me for a while.

Microsoft.Win32.Registry.LocalMachine.OpenSubKey(“subkey”).GetValue(“blah”) was failing with the error above, even though it worked perfectly previously and the key was clearly in the registry.

After a bit of research I found it to be because I’m now using a 64 bit version of Windows. Even though the key existed in HKEY_LOCAL_MACHINE\SOFTWARE\, it did not exist in HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\

To fix this, I simply created a copy of the key in Wow6432Node.

This may not be the correct solution but it worked for me…

Read MP3 ID3 Tags in Perl

Andrew — Thu, 03 Dec 2009 20:59:12 +0000

The package I use for simple tag reading is MP3::Tag, available on CPAN with more information here.

The following example shows how easy it is to retrieve tags from an MP3 file.

use MP3::Tag; my $file = MP3::Tag->new($filename); my ($title, $track, $artist, $album, $comment, $year, $genre) = $file->autoinfo(); print "Title: [$title]\n"; print "Artist: [$artist]\n"; print "Album: [$album]\n"; print "Track: [$track]\n"; print "Year: [$year]\n"; print "Genre: [$genre]\n"; print "Comment: [$comment]\n\n";

Add a space in XSL

Andrew — Fri, 13 Nov 2009 23:35:52 +0000

The following shows you how to add a space or in XSL:

disable-output-escaping="yes"> >

Specifically target each browser in CSS

Andrew — Fri, 13 Nov 2009 23:31:33 +0000

The following CSS ‘hack’ can be used to target all browsers IE 7, IE 6 and IE < 6 ...

All browsers:

margin-top: 44px;

IE7 and below:

*margin-top: 26px;

IE6 and below:

_margin-top: 44px;

IE6 only:

_mar\gin-top: 44px;

All firefox:

#selector[id=selector] { color: red; }

All firefox:

@-moz-document url-prefix() { .selector { color: red; } }

All Gecko:

*>.selector { color: red; }

Firefox 1.5 and newer:

.selector, x:-moz-any-link, x:only-child { color: red; }

Firefox 2 and older:

body:empty .selector { color: red; }

Firefox 2 and older:

#selector[id=SELECTOR] { color: red; }

Firefox 2 and older:

html>/**/body .selector, x:-moz-any-link { color: red; }

Firefox 3:

html>/**/body .selector, x:-moz-any-link, x:default { color: red; }

Use a button as an A Href link

Andrew — Fri, 13 Nov 2009 23:06:42 +0000

To create an A Href link that can be used as a button, we can use one of the two following methods:

function SubmitFrom(){ document.myform.target.value="somescript.php3" document.myfrom.submit() } function ResetFrom(){ document.myfrom.reset() } <a href="javascript:SubmitForm()"><img src=....>a>

or

<FORM name=remove ACTION='removeItem.php3' METHOD='POST' ENCTYPE='application/x- www-form-urlencoded'> <a href="javascript:document.remove.submit()">remove from cart</a> </form>

Run only one instance of a program in C#

Andrew — Fri, 13 Nov 2009 22:45:22 +0000

This example shows you how to ensure that only one instance of an application is running.

// Ensure only one instance of this application is running. bool alone = false; Mutex m = new Mutex(true, "", out alone); if (!alone) { Console.WriteLine("Another instance is already running."); Console.ReadKey(); return; } Console.WriteLine("Running...\n"); Console.ReadKey(); // Needed to ensure only one instance is running. GC.KeepAlive(m);

Restart a Windows service using C#

Andrew — Fri, 13 Nov 2009 22:38:05 +0000

This example shows how to start, stop and restart a windows service programmatically in C#.

Start service

The following method tries to start a service specified by a service name. Then it waits until the service is running or a timeout occurs.

public static void StartService(string serviceName, int timeoutMilliseconds) { ServiceController service = new ServiceController(serviceName); try { TimeSpan timeout = TimeSpan.FromMilliseconds(timeoutMilliseconds); service.Start(); service.WaitForStatus(ServiceControllerStatus.Running, timeout); } catch { // ... } }

Stop service

The following method tries to stop the specified service and it waits until the service is stopped or a timeout occurs.

public static void StopService(string serviceName, int timeoutMilliseconds) { ServiceController service = new ServiceController(serviceName); try { TimeSpan timeout = TimeSpan.FromMilliseconds(timeoutMilliseconds); service.Stop(); service.WaitForStatus(ServiceControllerStatus.Stopped, timeout); } catch { // ... } }

Restart service

This method combinates both previous methods. It tries to stop the service (and waits until it’s stopped) then it begins to start the service (and waits until the service is running). The specified timeout is used for both operations together.

public static void RestartService(string serviceName, int timeoutMilliseconds) { ServiceController service = new ServiceController(serviceName); try { int millisec1 = Environment.TickCount; TimeSpan timeout = TimeSpan.FromMilliseconds(timeoutMilliseconds); service.Stop(); service.WaitForStatus(ServiceControllerStatus.Stopped, timeout); // count the rest of the timeout int millisec2 = Environment.TickCount; timeout = TimeSpan.FromMilliseconds(timeoutMilliseconds - (millisec2-millisec1)); service.Start(); service.WaitForStatus(ServiceControllerStatus.Running, timeout); } catch { // ... } }