In computer programming, standard streams are preconnected input and output communication channels between a computer program and its environment when it begins execution. The three I/O connections are called standard input (stdin), standard output (stdout) and standard error (stderr). Originally I/O happened via a physically connected system console (input via keyboard, output via monitor), but standard streams abstract this. When a command is executed via an interactive shell, the streams are typically connected to the text terminal on which the shell is running, but can be changed with redirection, e.g. via a pipeline. More generally, a child process will inherit the standard streams of its parent process.

Application

Users generally know these streams as mediums by which text incoming from an input device and text outgoing to display are handled. As they are used for input and output devices, they generally contain text, a sequence of characters in a predetermined encoding, such as Latin-1 or UTF-8.