Opening a new tab in the same directory and then some in Mac OS

For all of you that use the Mac OS Terminal, you've probably felt the frustation of opening a new tab and it opening on the $HOME path, unlike the Linux one's, that open in the path you were in.

Well, I've written a script that kind of solves this problem, and adds some extra functionality that I find really helpfull.


#!/bin/bash

COMMAND=$1

if [ -z "$1" ]
then
  COMMAND="cd $(pwd)"
fi

/usr/bin/osascript 2>/dev/null <<EOF
activate application "Terminal"
tell application "System Events"
  keystroke "t" using {command down}
end tell
tell application "Terminal"
  activate
  do script "$COMMAND" in window 1
end tell
return
EOF


First let's take a look at the applescript part (that's the part between EOF). Applescript code is very readable, but what it does is to open a new tab in the terminal, and then run the code in the COMMAND variable in that newly open window.

Then, there is that little bit of bash code, that assigns the string passed as an argument to be run or, if none is provided, it changes the directory to the one you were in.

So, you can open a new tab, by calling the script or, and this is the very handy thing for writing other scripts, open a new tab and run code in that tab, by calling the script with the string as an argument.

An Objective-C/Cocoa character counter program

I've been learning Objective-C and Cocoa since yesterday (yes, I'm a newbie, so don't judge... :P), but I'm really loving it.

For those who have no idea of what this is, Objective-C is a C object oriented extension and Cocoa is, according to the Wikipedia, one of Apple Inc.'s native object-oriented API's for the Mac OS X operating system. Both of them together provide a great way to create programs to Mac OS X.

I'm not going to try to explain Objective-C or Cocoa in detail, there are really good books for that (the idea for this example was taken from Cocoa® Programming for Mac® OS X (3rd Edition)), nor will I explain how to use Xcode as an IDE. I'll just write the code and a little explanation of what it does.

So, let's get to what really matters, the code! :D

Every class in Obj-C is composed by two files a header file (.h) and a source file (.m). The first one has the instance variables and methods declarations and the second one the actual code (remember that Objective-C is an extension of C).

Our header file will be something like this:

#import <Cocoa/Cocoa.h>

@interface Counter : NSObject {
    IBOutlet NSTextField *line;
    IBOutlet NSTextField *output;
}

-(IBAction)count:(id)sender;
@end

The first line imports the declaration of NSObject which Counter inherits from, similar to Java's Object. All the Objective-C keywords start with @, to minimize conflicts with C code, as @interface.

Both instance variables are of type pointer to NSTextField, that can be either a text field or a label. IBOutlet is a macro that evaluates to nothing, it's a hint to the Interface Builder.

Finally, there's the method declaration. The method has the name count, returns IBAction (the same as void, also a hint for the IB) and has one argument named sender and of type id (a pointer to any type of object).

The .m file will have to implement the declared method (Java's public methods), but other methods can be declared as well, new methods (Java's private methods) or override inherited methods. Ours will be like this:


#import "Counter.h"

@implementation Counter

-(void)awakeFromNib
{
    [output setStringValue:@"???"];
}
   
-(IBAction)count:(id)sender
{
    NSString *theLine = [line stringValue];
    int noChars = [theLine length];
    NSLog(@"Counted %d chars",noChars);
    [output setStringValue:[NSString stringWithFormat:@"'%@' has %d characters", theLine, noChars]];
}   

@end


The nib file is a collection of objects that have been archived. When the program is launched, the objects are brought back to life before the application handles any events from the user. After being brought to life but before any events are handled, all objects are automatically sent the message awakeFromNib. This means that the label will have the string value "???" when the program starts, it should look like the following picture:

In the Interface Builder you should connect the text field and label to the corresponding outlets and the action of the button to the count method. For this you will have to add an object of the class Counter to the Doc Window.

Now, you've made sure the count method will be called when the button is pressed. So, what does the count method do?

It's actually a pretty simple method, it gets the string the user has typed, by sending the stringValue message to the text field (this method is an accessor, the correspondent to Java's get). It then sends the length message to the string, to get the number of characters. We now have all the information we need.

After that it writes the character number to the console, and finally it sets the label's string.

The final result should be something like this:

In this code I assume that you have a version of Mac OS above 10.4 and that you have the garbage collector on. I'll cover the usage of retain counts, the alternative solution to the GC in the future.

Writing to NTFS with Mac OS

I recently had the need to write to an NTFS formatted disk and found out that I only had read permissions. I could not have this, therefore, and after some Internet searching,  I found out how to do this. This "hack" is a really easy one, but really useful as well, nonetheless.

Native file handling capabilities of the Mac Os can be extended using Google's MacFUSE, as can be read at the project's home page. At the same page you can download the .dmg and install it.

You're halfway through. Now you just need the NTFS part, that can be downloaded here, install it, restart and you're good to go!

The Tuxera product needs a license after 15 days, if you find one that works just the same and is free, please tell me something.

*UPDATE*: See the comments for a free product.

Change the password on someone else's Mac OS

Every modern OS has a mode that grants you superuser permissions, without the need for a password. This mode is supposed to be used to run tasks that require exclusive access to shared resources or if you lost your password, for example.

The only reason this mode exists is because these OS's are seen as multiuser and the environment in which the computer is set should be a friendly one. Nevertheless this mode, the single user mode, can be used for some very nasty things if you now your BASH (or the existing shell) basics. Here we're going to change the root password.

First, you have to turn the computer off, because this mode is entered at boot time. While the system is booting keep cmd+S pressed, until a console appears. When it does, you're good to go. Just mount the file system with mount -wu /.

Now for the final step, type passwd and return. You should be asked to enter the new root password twice. Once that's done, you have successfully gained root rights to the OS. Reboot it and try it out!

If you want to be "protected" from this, you can install SecureIt, that requests you to enter a password before showing the console, when booting.

Notes:

1. You cannot enter single user or verbose mode if the computer owner or administrator has enabled Open Firmware Password Protection.
2. When in single-user mode, the keyboard layout is US English.
3. In Linux systems you have to change the configuration of the booter, can be easily done
4. In Windows there's the Safe Mode