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Before talking about redirection of streams, let me quickly summarize key points of what we know so

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far.

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Every process has three different data streams.

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stdIn stdout and stderr.

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And by default, when you are connected to shell and start corresponding process like mkdir you name

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or something else.

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Picture looks like this.

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There was keyboard and using keyboard, you enter some commands and those commands are sent to stdin

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of the shell.

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Because Shell is also a process like bash, shell or shell and it also has those three data streams

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stdin stdout and stderr.

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And when you go to the terminal and enter ls, you actually interact with stdin of shell process.

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And inside of that process it creates one more process and connects to stdin of that process.

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In this example LS process also by default there will be connection from stdout and stderr data streams

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of new process to corresponding shell process.

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And that's why if I enter LHS here and press enter, I see this output in the terminal.

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That's because data stream from LHS process STD out was redirected to Schell process and Schell process

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has printed this result to the screen.

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That's how it works.

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Same applies to stderr data stream.

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If I enter again mkdir without any arguments, I see text that was produced by stderr of mkdir process.

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It was sent to Schell process and Schell process has produced this error to the screen.

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That's how it works.

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But afterwards, when I have tried to redirect output from stdout of specific process to the file,

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we have tried that above using command.

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This one, For example, we have redirected STD out data stream of RLS process to the file.

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I have changed this default behavior and I have moved STD out stream to the file.

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Here I have sent output from STD out to the file like this.

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All right, let's now proceed.

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And next, let me explain you what are numeric ids of stdin stdout and stderr and how you could redirect

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simultaneously stdout data stream and stderr data stream.

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And also I will show you first example of the process that accepts data via stdin data stream because

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actually LHS and mkd are processes.

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Don't accept any input via stdin.

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You are not able to supply some additional text to stdin of LHS process.

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All right, let's proceed and I will see you next.

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Bye.