Reading Data from a File Once a file has been opened and assigned a file handle, the contents of that file may be read from the current offset position.
To delete the entire contents of a file, specify an offset of 0 when calling this method: Note that this does not insert data but rather overwrites any existing data in the file at the corresponding location. As discussed in the previous chapter, the NSFileManager class contains a class method named defaultManager that is used to create an instance of the class.
As with the move method, this takes as arguments the source and destination pathnames and an optional NSError object. The data read is returned encapsulated in an NSData object: This method takes as arguments the paths to the two files to be compared and returns a boolean YES or NO to indicate whether the file contents match: Without knowing where the current offset is in a file it is impossible to know where in the file data will be read or written.
The following example opens a file for reading and then performs a number of method calls to move the offset to different positions, outputting the current offset after each move: This means that any read or write operations we perform using the NSFileHandle methods will take place at offset 0 in the file.
Writing Data to a File The writeData method writes the data contained in an NSData object to the file starting at the location of the offset. As such, it is not a certainty that your program will have read or write access to a particular file, or the appropriate permissions to delete or execute it.
This is referred to as the offset. When a file is first opened the offset is set to 0 the beginning of the file. For example to move the current offset to the end of the file, use the seekToEndOfFile method.
Finally, the current offset may be identified using the offsetInFile method. This takes as arguments the path of the symbolic link, the path to the file to which the link is to refer and an optional NSError object.
If no error description information is required, this argument may be set to NULL. For example, the following code excerpt checks to find out if a file is writable: In addition to files, this class can also be used for working with devices and network sockets.
The quick brown fox jumped over the lazy dog Next, we will write a program that opens the file for updating, seeks to position 10 and then writes some data at that location:. Join GitHub today. GitHub is home to over 28 million developers working together to host and review code, manage projects, and build software together.
Replace a file using the NSSavePanel in a sandboxed application at elonghornsales.com | Latest informal quiz & solutions at programming language problems an. I'd like to suggest that a new init() function be added that has another flag to specify the type of log rotation desired (size, time) and number of rotations (history of files to keep).
The logger would simply append a rotating integer (number of rotations-1) that is being used. On launch the logger would append instead of overwrite the file. Replace a file using the NSSavePanel in a sandboxed application at elonghornsales.com | Latest informal quiz & solutions at programming language problems an.
HYFileManager A Practical Tools Of File Operations.
HYFileManager is a simple tool of iOS file operations base on NSFileManager. It offers a range of static methods, only a small amount of code to handle file operations often need to deal with, making work easier and faster. Labels: Create File, Delete File, IOS, NSFileManager, Read File, Rename File, Write File On iOS Programming, one of the most frequent tasks is Manipulation with Files.
Using Local Files is one of the most efficient way to store your local data, other ways may include NSUserDefault, Core Data, but local files is very easy to be implemented and organized.Createfileatpath overwrite a file