FILE HANDLING IN C

TYPES OF FILES�

• When dealing with files, there are two types of files you should know about:
• Text files
• Binary files

​

 TEXT FILES�

• Text files are the normal .txt files. We can easily create text files using any simple text editors such as Notepad.
• When We open those files, we'll see all the contents within the file as plain text. We can easily edit or delete the contents.

​

TEXT FILES�

• File handling in C is the process in which we create, open, read, write, and close operations on a file.
• C provides different functions such as fread(), fseek(), fprintf(), etc. to perform input, output, and many different C file operations in our program.

OPENING A FILE

• Before we perform any operations on a file, we need to open it.
• We do this by using a file pointer.
• The type FILE defined in stdio.h allows us to define a file pointer. Then you use the function fopen() for opening a file.
• Once this is done one can read or write to the file using the fread() or fwrite() functions, respectively.

2. BINARY FILES�

• Binary files are mostly the .bin files in your computer.

​

• Instead of storing data in plain text, they store it in the binary form (0's and 1's).

​

FILE OPERATIONS�

• In C, we can perform four major operations on files, either text or binary:
• Creating a new file
• Opening an existing file
• Closing a file
• Reading from and writing information to a file

​

WORKING WITH FILES�

• When working with files, you need to declare a pointer of type file. This declaration is needed for communication between the file and the program.
• FILE *fptr;

​

OPENING A FILE - FOR CREATION AND EDIT�

• Opening a file is performed using the fopen() function defined in the stdio.h header file.
• The syntax for opening a file in standard I/O is:

​

SYNTAX OF FOPEN()�

​

• FILE* fopen(*file_name, *access_mode);
• Parameters
• file_name: name of the file when present in the same directory as the source file. Otherwise, full path.
• access_mode: Specifies for what operation the file is being opened.

​

​

CREATE/OPEN A FILE

• Example

​

• fp = fopen(“one.txt", "r");

​

RETURN VALUE�

​

• If the file is opened successfully, returns a file pointer to it.

​

​

• If the file is not opened, then returns NULL.

​

FILE OPENING MODES�

• File opening modes or access modes specify the allowed operations on the file to be opened.
• They are passed as an argument to the fopen() function. Some of the commonly used file access modes are listed below:

​

FILE ACCESS_MODE

• File Mode Description
• r Open a text file for reading
• w Create a text file for writing, if it exists, it is overwritten.
• a Open a text file and append text to the end of the file.
• rb Open a binary file for reading
• wb Create a binary file for writing, if it exists, it is overwritten.
• ab Open a binary file and append data to the end of the file.

FILE ACCESS_MODE

• r+ Open the existing file for both reading and writing

​

• w+ Open the file for both reading and writing

​

• a+ Open the file for both appending and reading
•  

​

FCLOSE()

​

• The fclose() function is used for closing opened files. The only argument it accepts is the file pointer.
• If a program terminates, it automatically closes all opened files. But it is a good programming habit to close any file once it is no longer needed.

​

• fclose(FILE *fp);

WRITE TO A FILE�

​

• The file write operations can be performed by the functions fprintf() and fputs().
• C programming also provides some other functions that can be used to write data to a file such as:

​

READING FROM A FILE�

• The file read operation in C can be performed using functions fscanf() or fgets().
• Both the functions performed the same operations as that of scanf() and gets but with an additional parameter, the file pointer.
• There are also other functions we can use to read from a file. Such functions are listed below:

​

READING FROM A FILE

READING AND WRITING TO A BINARY FILE�

• Functions fread() and fwrite() are used for reading from and writing to a file on the disk respectively in case of binary files.
•  

​

WRITING TO A BINARY FILE�

• To write into a binary file, we need to use the fwrite() function. The functions take four arguments:
• address of data to be written in the disk
• size of data to be written in the disk
• number of such type of data
• pointer to the file where we want to write.

​

SYNTAX

• fwrite(addressData, sizeData, numbersData, pointerToFile);

​

READING FROM A BINARY FILE�

• Function fread() also take 4 arguments similar to the fwrite() function as above.
• fread(addressData, sizeData, numbersData, pointerToFile);

​

GETTING DATA USING FSEEK()�

• The fseek() function is used to move the file pointer associated with a given file to a specific location in the file.
• It provides random access capabilities, which allow the programmer to randomly move the file pointer to any location in the file to read or write data.

FSEEK

SYNTAX OF FSEEK()�

• fseek(FILE * stream, long int offset, int position);

​

FTELL()

• The ftell() function in C is part of the standard input/output library (<stdio.h>) and is used to retrieve the current position of the file position indicator for a specified file stream. 
•  ftell() is used to determine the position of the file pointer in the file from the beginning of the file
• This position is typically measured in bytes from the beginning of the file.
• syntax
• long int ftell(FILE *stream);

FGETC()

• fgetc() is used to obtain input from a file single character at a time. 
• int fgetc(FILE *pointer)

​

FGETS() FUNCTION

• The fgets() function in C is a standard library function used for reading a string from a specified input stream. It is part of the <stdio.h> header file and provides a safer alternative to gets() by preventing buffer overflows.
• char *fgets(char *str, int n, FILE *stream);

FSCANF (FILE SCAN FORMATTED):�

• Formatted input: 
• fscanf reads formatted input from a file stream, attempting to match the input with a specified format string. It can directly convert text representations to various data types (integers, floats, strings, etc.).
• fscanf(FILE *stream, const char *format, ...);