fopen in C: File Opening Explained

The fopen function is used in the C programming language to open files, and its usage is as follows:

Open a file with the specified name and mode.

In this case, filename is the name of the file to be opened, and mode is the mode in which the file should be opened. The modes can include the following options:

1. “r”: Open the file in read-only mode, the file must exist.
2. “w”: Open the file in writing mode, truncate the file if it exists, or create the file if it doesn’t exist.
3. Option: “Open the file in append mode, create the file if it doesn’t exist, and position the file pointer at the end of the file.”
4. “r+”: Open the file in read-write mode, the file must exist.
5. Open the file for reading and writing, truncating the file if it already exists or creating it if it does not.
6. “a+” : open the file for reading and writing, create the file if it doesn’t exist, the file pointer points to the end of the file.

The fopen function returns a pointer to a FILE structure. If the file opening fails, it returns NULL. After successfully opening a file, you can use this pointer to read and write files. Remember to use the fclose function to close the file after completing the operation.