The Old New Thing

Quotation marks around spaces aren't necessary in the PATH environment variable

September 29, 2006 Sep 29, 2006 09/29/06

Raymond Chen

The purpose of quotation marks is to allow a character that would normally be interpreted as a delimiter to be included as part of a file name. Most of the time, this delimiter is the space. The function uses a space to separate the program name from its arguments. Most programs separate their command line arguments with a space. But the ...

The redirection operator can occur in the middle of the command line

May 18, 2006 May 18, 2006 05/18/06

Raymond Chen

Although the redirection operator traditionally appears at the end of a command line, there is no requirement that it do so. All of these commands are equivalent: All of them echo "A B" to the file "C". You can use this trick to avoid the redirection problem we discussed last time. We saw that writing inadvertently interprets the "2...

Beware of digits before the redirection operator

May 17, 2006 May 17, 2006 05/17/06

Raymond Chen

If you want to put the string "Meet at 2" into the file "schedule", you might be tempted to use If you try this, however, you'll see the string "Meet at" on the screen and the "schedule" file will be blank. [Typo fixed, 10am] What happened? A digit immediately before a redirection operator modifies which stream the redirection operator...

Command line redirection is performed by the command line interpreter

May 16, 2006 May 16, 2006 05/16/06

Raymond Chen

The magic characters like <, >, and | in command lines like are interpreted by the command interpreter ; they aren't built into the function. (This is obvious if you think about it. That command line created two processes; which one should return a handle to?) If you pass a command line like this to , it will merely run the ...

Doing quick arithmetic from the command prompt

May 4, 2006 May 4, 2006 05/4/06

Raymond Chen

The command processor comes with a mini-calculator that can perform simple arithmetic on 32-bit signed integers: Note that we had to quote the shift operator since it would otherwise be misinterpreted as a "redirect stdout and append" operator. For more information, type at the command prompt...

The ForceAutoLogon setting doesn't do what most people think

March 6, 2006 Mar 6, 2006 03/6/06

Raymond Chen

The folks on the logon team wish me to remind you that the ForceAutoLogon setting does more than just log on an account automatically. They've had to deal with large numbers of people who set the key without really understanding what it does, and then getting into trouble because what they get is not what they expected. In addition to ...

Why do words beginning with "home" get treated as URLs?

January 13, 2006 Jan 13, 2006 01/13/06

Raymond Chen

Vitaly from the Suggestion Box asked (with grammatical editing), Could you explain why Windows starts the web browser if the file name passed to ShellExecute starts with "home". First thing to note is that this URL-ization happens only after the function has tried all the other possible interpretations. If a file named "homestar" is ...

The undeletable Outlook folder

October 17, 2005 Oct 17, 2005 10/17/05

Raymond Chen

For a while, I've had a few "undeletable Outlook folders". Even after deleting all the messages from them, Outlook just complains when I try to delete them. There was some sort of error message, but of course I didn't read it. The only option was OK, so I clicked it. As I recall, the message said something about "Can't delete because blah ...

Windows Server 2003 can take you back in time

September 6, 2005 Sep 6, 2005 09/6/05

Raymond Chen

If you are running Windows Server 2003, you owe it to yourself to enable the Volume Shadow Copy service. What this service does is periodically (according to a schedule you set) capture a snapshot of the files you specify so they can be recovered later. The copies are lazy: If a file doesn't change between snapshots, a new copy isn't made. Up...