09_connecting_things_together.md

Connecting Things Together

Normally output and errors goes to stdout, the terminal, and input comes from stdin, the keyboard. Stdin, stdout, and stderr are data streams.

                    +---------------+ 
                    |               |-----> STDOUT(1)
     STDIN(0) ----->|    Program    |
                    |               |
                    +---------------+ 
                               |
                               |
                               +------> STDERR(2)

Sometimes we don't want this. We can move data from output/input/error streams to/from a file using redirection. We can also combine several commands together with piping.

Redirection

Redirection is all about files.

When we redirect input to a command, data is taken from a file by redirecting the stdin stream. When we redirect output to a file, output from a command is sent to a file by redirecting the output stream.

Redirect Input and Output

Piping

Piping is all about processes.

With piping, we connect the stdout of one command to the stdin of another command as if there were a pipe or a stream of data between the two.

Piping Commands Together

Back: Reading User Input Forward: Redirect Input and Output