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Working with Files in C

File handling in C enables you to store data permanently on a storage device. By using file operations, you can create, write, read, and manipulate files directly from your C programs.

Key Topics

1. Basic File Operations

The basic operations that can be performed on files are:

  • Creating a new file
  • Opening an existing file
  • Reading from a file
  • Writing to a file
  • Closing a file

2. File Pointers

In C, files are managed using a file pointer of type FILE *. This pointer is used to access and manipulate files.

FILE *fptr;

3. Opening and Closing Files

Files are opened using the fopen() function and closed using the fclose() function.

Example: Opening a File

FILE *fptr;
fptr = fopen("filename.txt", "r"); // Open file for reading
if (fptr == NULL) {
    printf("Error opening file!\n");
    exit(1);
}

File Modes

Mode Description
"r"Open for reading. The file must exist.
"w"Open for writing. Creates a new file if it doesn't exist or truncates the file if it exists.
"a"Open for appending. Data is added to the end of the file.
"r+"Open for both reading and writing. The file must exist.
"w+"Open for reading and writing. Creates a new file if it doesn't exist or truncates the file if it exists.
"a+"Open for reading and appending. Creates a new file if it doesn't exist.

Example: Closing a File

fclose(fptr);

Best Practices

  • Always check if the file was opened successfully.
  • Close files using fclose() to free resources.
  • Use appropriate file modes based on the required operations.

Key Takeaways

  • File handling allows data to be stored and retrieved from files.
  • Use FILE * pointers to manage files.
  • Properly opening and closing files is crucial for resource management.
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