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FILE OPEN MODES

FILE OPEN MODES. File open modes. ios::app ios::ate ios::binary ios::in ios::out ios::trunc ios::nocreate ios::noreplace. ios::app. Write all output to the end of file, no matter how you set the seekp pointer. ofstream: open file, write data to the end of file.

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FILE OPEN MODES

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  1. FILE OPEN MODES

  2. File open modes • ios::app • ios::ate • ios::binary • ios::in • ios::out • ios::trunc • ios::nocreate • ios::noreplace

  3. ios::app • Write all output to the end of file, no matter how you set the seekp pointer. • ofstream: open file, write data to the end of file. • ifstream: open file, read data from file. • fstream: open file, write data to the end of file, BUT cannot read data from file. • If the file does not exist, the program will create a new file.

  4. Before Alex Zhao Andrew Nguyen Vincent Tran After Alex Zhao Andrew Nguyen Vincent Tran Tyler Price Example fstream File (“myFile.txt”, ios::app); File.seekp (0);File << “Tyler Price”;

  5. ios::ate • Open a file for output and move pointer to the end of file. Data can be write anywhere in the file. • ofstream: open file, write data to the end of file. • ifstream: open file, but CANNOT read data • fstream: CANNOT open file. • If the file does not exist, the program will create a new file.

  6. Before Alex Zhao Andrew Nguyen Vincent Tran After Tyler PriceAndrew Nguyen Vincent Tran Example fstream File (“myFile.txt”, ios::ate); File.seekp (0);File << “Tyler Price”;

  7. ios::binary • Open a file for binary input and output. • ofstream: open file, discard the file’s content, write data to the file. • ifstream: open file, discard the file’s content. • fstream: CANNOT open file. • If the file does not exist, the program will create a new file.

  8. Before Alex Zhao Andrew Nguyen Vincent Tran After Tyler Price Example ostream File (“myFile.dat”, ios::binary); File .write (interpret_cast <const char *> (&data), sizeof (data));

  9. ios::in • Open a file for input. • ofstream: not support ios::in. • ifstream: open file, read data from file. • fstream: open file, read data from file. • If the file does not exist, the program will create a new blank file.

  10. ios::out • Open a file for output. • ofstream: open file, discard the file’s content, then • write data to the file. • ifstream: not support ios::out. • fstream: open file, discard the file’s content, then • write data to the file. • If the file does not exist, the program will create a new file.

  11. Before Alex Zhao Andrew Nguyen Vincent Tran After Tyler Price Example ostream File (“myFile.txt”, ios::out); File << “Tyler Price”;

  12. ios::trunc • Discard the file’s contents if it exists. • ofstream: open file, discard the file’s content, then • write data to the file. • ifstream: open file, discard the file’s content. • fstream: open file, discard the file’s content, then • write data to the file. • If the file does not exist, the program will create a new file.

  13. ios::nocreate • ofstream: open file, discard the file’s content, then • write data to the file. • ifstream: open file, read data from file. • fstream: cannot open file. • If the file does not exist, the open operation fails.

  14. ios::noreplace • If the file exists, the open operation fails. • ofstream: create a file, then write data to the file. • ifstream: create a blank file. • fstream: cannot open file.

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