Shell tutorial part 14: advanced output redirection in tcsh скачать в хорошем качестве

Shell tutorial part 14: advanced output redirection in tcsh

We will learn about the standard & error outputs and how to redirect them using !, &, /dev/null, /dev/tty. Note: although most other shells can perform advanced redirection as shown in this video, usually the syntax for them is a bit different. So, if you want to use other shells instead of tcsh - read up on their advanced redirection syntax. ----------------------- Video content: 00:57 : single right-angled-bracket ! |file-path|. By using ! together with a single right-angled-bracket, we can "force" the shell to perform the redirection, even if the supplied path already exists. If it does exist, the shell will overwrite it with the new output (erase the previous content and then enter the new content). If it doesn't exist, it will work exactly as using a right-angled-bracket without !. 1:55 : double-right-angled-bracket ! |file-path|. By using ! together with a double-right-angled-bracket, we can "force" the shell to perform the redirection, even if the supplied path doesn't exists. If it doesn't exist, the shell will create the new file and then append the new output to the end of the file. If it does exist, it will work exactly as using a double-right-angled-bracket without !. 3:03 : Every command has two outputs - the error output (also called stderr), which is used for printing error messages, and the standard output (also called stdout), which is used for printing everything else. Using right-angled-bracket or double-right-angled-bracket, with or without !, we can only control stdout. 4:42 : &. By writing & after right-angled-bracket or double-right-angled-bracket (with or without !) we can redirect both stdout and stderr at the same time. 5:44 : stdout and stderr can be redirected to different files, by first redirecting stdout (using right-angled-bracket or double-right-angled-bracket) inside parentheses ('(' ')') and the using right-angled-bracket or double-right-angled-bracket together with & outside the parentheses. 7:25 : /dev/null. This path is the "trash-can" of the operating system - everything redirected to it is thrown away; not saved anywhere and not printed on the screen. 8:13 : /dev/tty. This path represents the current shell - everything redirected to it is printed in the shell. A note: you can mix all these different techniques together! Try it. ----------------------- Relevant links: The complete pipleining and input/output redirection playlist:    • Pipelining and input/output redirection   The complete shell tutorial playlist:    • A short tutorial to using the command line...