What is FILE in C? What is the size of that?

Understanding FILE in C

Introduction

• In C programming, a FILE is a data structure used for performing operations on files.
• It provides a way to read from and write to files in a structured manner.

Anatomy of a FILE

A FILE is typically represented as a pointer to a structure.

The structure contains information about the file, such as its name, status flags, and current position.

FILE structure includes members like:

• _ptr: A pointer to the buffer, which holds the data read from or written to the file.
• _cnt: An integer representing the number of characters left in the buffer.
• _base: A pointer to the start of the buffer.
• _flag: An integer containing status flags for the file.
• _file: An integer representing the file descriptor.

Functions for FILE Handling

• fopen(): Used to open a file and return a pointer to the FILE structure.
• fclose(): Closes a file.
• fread(): Reads data from a file.
• fwrite(): Writes data to a file.
• fseek(): Sets the file position indicator.

Size of FILE

• The sizeof(FILE) may vary depending on the C compiler and system architecture.
• On most systems, the size of a FILE structure is typically around 64 to 128 bytes.
• It's essential to note that the exact size isn't standardized and can differ from one system to another.

Usage of FILE in C:

• Opening a File: To work with files, you usually open them using functions like fopen.
• Reading and Writing: Once a file is open, you can use functions like fread and fwrite to read from and write to the file, respectively.
• Closing a File: It's crucial to close a file using fclose when you're done with it to free up system resources.

Common FILE Operations:

• Reading from a File: Use fread or fgets to read data from a file.
• Writing to a File: Use fwrite or fprintf to write data to a file.
• Closing a File: Always close the file using fclose when finished.

Common Mistakes

• Forgetting to close a file after use can lead to resource leaks.
• Not checking the return value of fopen() for errors.

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Conclusion

• Understanding how to work with FILE in C is crucial for efficient file handling.

• Proper use of file functions ensures that your programs interact with files correctly.