Modes   | Description
r Open a file for read only. File pointer starts at the beginning of the file
w Open a file for write only. Erases the contents of the file or creates a new file if it doesn’t exist. File pointer starts at the beginning of the file
a Open a file for write only. The existing data in file is preserved. File pointer starts at the end of the file. Creates a new file if the file doesn’t exist
x Creates a new file for write only. Returns FALSE and an error if file already exists
r+ Open a file for read/write. File pointer starts at the beginning of the file
w+ Open a file for read/write. Erases the contents of the file or creates a new file if it doesn’t exist. File pointer starts at the beginning of the file
a+ Open a file for read/write. The existing data in file is preserved. File pointer starts at the end of the file. Creates a new file if the file doesn’t exist
x+ Creates a new file for read/write. Returns FALSE and an error if file already exists

When you open the file do you want to create the file, then write to it or do you want to open the file and append to it?

For creating/writing/reading use w+
For opening/appending/reading use r+

“r”
Open a file for reading. The file must exist.

“w”
Create an empty file for writing. If a file with the same name already exists its content is erased and the file is treated as a new empty file.

“a”
Append to a file. Writing operations append data at the end of the file. The file is created if it does not exist.

“r+”
Open a file for update both reading and writing. The file must exist.

“w+”
Create an empty file for both reading and writing. If a file with the same name already exists its content is erased and the file is treated as a new empty file.

“a+”
Open a file for reading and appending. All writing operations are performed at the end of the file, protecting the previous content to be overwritten. You can reposition the internal pointer to anywhere in the file for reading, but writing operations will move it back to the end of file. The file is created if it does not exist.

Advertisements