I/O Operations with File Systems

File Input And Output

•          The file is a collection of data stored on a disk with a specific name and very often with a directory path.

•          When we open the file for reading data or writing data, it becomes a stream.

•          Stream is a sequence of bytes travelling from source to a destination over a communication path.

•          The operations use the namespace “System.IO”

Two basic streams are:

•        Input Stream: used for a read operation

•        Output Stream: used for performing a write operation.

Class Name	Description
FileStream	Used to read from and write to any location within a file.
BinaryReader	Used to read primitive data types from a binary stream.
BinaryWriter	Used to write primitive data types in binary format.
StreamReader	Used to read characters from a byte stream.
StreamWriter	Used to write characters to a stream.
StringReader	Used to read from a string buffer.
StringWriter	Used to write into a string buffer.
DirectoryInfo	Used to perform operations on directories.
FileInfo	Used to perform operations on files.

FileStream Class

•          We can use the FileStream class in the System.IO namespace to read from, to write and to close files.

•          This class inherits from the abstract class “Stream”.

FileStream = new FileStream(,

, ,)

FileMode Enumerator

Defines various methods for opening files.

FileMode	Functionality
Append	Opens the file if it exists and places the cursor at the end of the file or creates new line
Create	Creates a new file.
CreateNew	Specifies to an operating system that is should create a new file.
Open	Opens an existing file.
OpenOrCreate	Specifies to the operating system that it should open a file if it exists,  else create new file.
Truncate	Opens an existing file and truncate it to zero bytes.

File Access Enumerator

This enumerator indicates wheather you want to read data from the file, write to the file, or perform both the operations.

The member of the FileAccess enumerator are:

•          Read

•          ReadWrite

•          Write

FileShare Enumerator

FileShare	Functionality
Inheritable	Allows a file handle to pass inheritance to the child processes.
None	Declines sharing of a current file.
Read	Allows opening of a file for reading purpose.
ReadWrite	Allows opening a file for the purpose of reading and writing.
Write	Allows opening of a file for writing purpose.

StreamReader Class

FileStream fs = new FileStream(“C://Myfile.txt”,FileMode.Open,FileAccess.Read);

StreamReader sr = new StreamReader(fs);

Methods	Description
Close	Closes the object of StreamReader class and the underlying stream, and releases any system resources associated with the reader.
Peek	Returns the next available character but does not consume it.
Read	Reads the next character or the next set of character but does not consume it.
ReadLine	Reads a line of characters from the current stream and returns data as a string.
Seek	Allows the read/write position to be moved to any position within the file.

using System;

using System.IO;

Class FileRead

{

            public void ReadData()

            {

                        FileStream fs = new FileStream(“C://Myfile.txt”,FileMode.Open,FileAccess.Read);

                        StreamReader sr = new StreamReader(fs);

                        sr.BaseStram.Seek(0,SeekOrigin.Begin);

                        string str = sr.ReadLine();

                        while(str!=null)

                        {

                                    Console.WriteLine(“{0}”,str);

                                    str = sr.ReadLine();

                        }

                        sr.Close();

                        fs.Close();

            }

            public static void Main(String[] args)

            {

                        FileRead fr = new FileRead();

                        fr.ReadData();

            }

}

StreamWritter class

The StreamWriter class is inherited from the abstract class TextWritter.

Methods	Description
Close	Closes the current StreamWriter object and the underlying stream.
Flush	Clears all buffers for the current writer and causes any buffered data to be written to the underlying stream.
Write	Writes to the stream.
WriteLine	Writes data specific by the overloaded parameters followed by end of line.

using System;

using System.IO;

Class FileWrite

{

            public void WriteData()

            {

                        FileStream fs = new FileStream(“C://Myfile.txt”,FileMode.Open,FileAccess.Write);

                        StreamWriter w = new StreamWriter(fs);

                        Console.WriteLine(“Enter a string”);

                        string str = Console.ReadLine();

                        w.Write(str);

                        w.Flush();

                        w.Close();

                        fs.Close();

            }

            public static void Main(String[] args)

            {

                        FileWrite fw = new FileWrite();

                        fw.WriteData();

            }

}

DirectoryInfo Class

Property	Description
Attributes	Gets or sets the attributes associated with the file. This property is inherited from FileSystemInfo.
Creationtime	Gets or sets the creation time of the file.
Exists	Gets a boolean value indicating whether the directory exists or not.
Extension	Gets a string containing the file extension.
FullName	Gets a string containing full path of the directory.
LastAccessTime	Gets a string containing time of the directory.
Name	Gets a string containing the name of a given file.
Create	Create a directory.
CreateSubdirectory	Creates a directory.
Delete	Delete a directory.

FileInfo Class

Property	Description
Attributes	Gets or sets attributes associated with the file. This property is inherited from File SystemInfo.
CreationTime	Gets or sets Creation time of the current file.
Directory	Gets an instance of the directory which the file belongs to.
Exists	Gets a boolean indicating whether the file exists or not.
Extension	Gets a string containing the file extention.
FullName	Gets a string containing the full path of the file.
LastAccessTime	Gets the last accessed time of the file.
LastWriteTime	Gets the time of the last written activity of the file.
Length	Gets the size of the file.
Name	Gets a string contatining the name of a given file.
Create	Creates a file.
AppendText	Appends a text to the file represented by the FileInfo object
Delete	Deletes a file.
Open	Opens file.
OpenRead	Opens a file in read-only mode.

using System;

using System.IO;

Class Tester

{

            public static void Main()

            {

                        DirectoryInfo mydir = new DirectoryInfo(@”c:\Windows”);

                        FileInfo[] FileInDir = mydir.GetFiles();

                        foreach(FileInfo file in FileInDir)

                        {

                                    Console.WriteLine(“File Name: {} Size: {1} bytes”,file.Name,file.Length);

                        }

            }

}

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