Input and Output (Windows CE 5.0)
Developing an Application > Microsoft C Run-time Library for Windows CE > Run-time Routines by Category
Input and output functions process data in different sizes and formats, from single characters to large data structures.
These functions also provide buffering, which can improve performance. The default size of a stream buffer is 4K.
Input and output functions affect buffers created by the run-time library routines and have no effect on buffers created by the OS.
| Routine | Use |
|---|---|
| clearerr | Clears error indicator for stream |
| fclose, _fcloseall | Closes stream |
| feof | Tests for end of file on stream |
| ferror | Tests for error on stream |
| fflush | Flushes stream to buffer or storage device |
| fgetc, fgetwc | Reads character from stream |
| fgetpos | Gets position indicator of stream |
| fgets, fgetws | Reads string from stream |
| _fileno | Gets file handle associated with stream |
| _flushall | Flushes all streams to buffer or storage device |
| fopen, _wfopen | Opens stream |
| fprintf, fwprintf | Writes formatted data to stream |
| fputc, fputwc | Writes a character to a stream |
| fputs, fputws | Writes string to stream |
| fread | Reads unformatted data from stream |
| fscanf, fwscanf | Reads formatted data from stream |
| fseek | Moves file position to given location |
| fsetpos | Sets position indicator of stream |
| ftell | Gets current file position |
| fwrite | Writes unformatted data items to stream |
| getchar, getwchar | Reads character from stdin |
| gets, _getws | Reads line from stdin |
| printf, wprintf | Writes formatted data to stdout |
| putchar, putwchar | Writes character to stdout |
| puts, _putws | Writes line to stream |
| scanf, wscanf | Reads formatted data from stdin |
| _snprintf | Writes formatted data of specified length to string |
| sprintf, swprintf | Writes formatted data to string |
| sscanf, swscanf | Reads formatted data from string |
| ungetc, ungetwc | Pushes character back onto stream |
| vfprintf, vfwprintf | Writes formatted data to stream |
| vprintf, vwprintf | Writes formatted data to stdout |
| _vsnprintf, _vsnwprintf | Writes formatted data of specified length to buffer |
| vsprintf, vswprintf | Writes formatted data to buffer |
| _wfdopen | Associates a stream with a file opened for low-level IO |
| _wfreopen | Reassigns a file pointer |
When a program begins execution, the startup code automatically opens several streams: standard input (pointed to by stdin), standard output (pointed to by stdout), and standard error (pointed to by stderr). These streams are directed to the console (keyboard and screen) by default.
Files opened using the stream routines are buffered by default. The stdout and stderr functions are flushed whenever they are full or, if you are writing to a character device, after each library call.
If a program terminates abnormally, output buffers may not be flushed, resulting in loss of data. Use fflush or _flushall to ensure that the buffer associated with a specified file or all open buffers are flushed to the operating system, which can cache data before writing it to disk.
The commit-to-disk feature ensures that the flushed buffer contents are not lost in the event of a system failure.
There are two ways to commit buffer contents to disk:
- Link with the file COMMODE.OBJ to set a global commit flag. The default setting of the global flag is n, for no-commit.
- Set the mode flag to c with fopen or _fdopen.
Any file specifically opened with either the c or the n flag behaves according to the flag, regardless of the state of the global commit/no-commit flag.
If your program does not explicitly close a stream, the stream is automatically closed when the program terminates. However, you should close a stream when your program finishes with it, as the number of streams that can be open at one time is limited.
Input can follow output directly only with an intervening call to fflush or to a file-positioning function (fseek, fsetpos, or rewind). Output can follow input without an intervening call to a file-positioning function if the input operation encounters the end of the file.
See Also
Microsoft C Run-time Library for Windows CE | Run-time Library Reference
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