2.5. Standard I/O Streams

When a file is opened with append mode, the file position indicator is initially positioned at the beginning of the file.

The characteristics of unbuffered and fully buffered streams are supported.

Fully buffered streams use all bytes in the allocated buffer.

Line buffered streams are supported for all file types.

Note: As a QNX Neutrino extension, you can use the STDIO_DEFAULT_BUFSIZE environment variable to override BUFSIZ as the default buffer size for stream I/O. The value of STDIO_DEFAULT_BUFSIZE must be greater than that of BUFSIZ.

2.5.1. Interaction of File Descriptors and Standard I/O Streams

Input is seen exactly once provided the application follows the rules specified.