Sometimes called "switches", they are tailored to the needs of different user groups. Or they simply do not want to control one as they are power users (see below).Ĭomputers (and all their standard software) can flawlessly be controlled without a pointing device (for example a mouse) by using system wide and application specific keyboard shortcuts and quick keys.Įven for users who are not able to control a common keyboard, there are various special input devices.Either they cannot control one due to a motor impairment.Many users do not use a mouse (or similar pointing device): For macOS, Linux, and others, there exist similar keyboard shortcuts. Notice: we are talking specifically about Windows operating systems here. This does not only benefit disabled users, but also power users. Thus, it's crucial that any software (including websites) is operable by keyboard only. Many users control a computer using keyboard only, so no mouse or similar pointing device is available. Live the good life and use redirection.Controlling a computer with a keyboard only You may not use redirection all the time, but learning to use it when you need it can save you a lot of needless opening files and copying and pasting data, all of which generally require mouse movement and lots of key presses. Redirection is an efficient way to get data from one place to another in Bash. The find command processes that as an error, so you can redirect just the error messages to /dev/null: $ find ~ -type f 2> /dev/null For instance, the find command tends to be verbose, and it often reports permission conflicts while searching through your files: $ find ~ -type fįind: `/home/seth/foggy': Permission deniedįind: `/home/seth/groggy': Permission deniedįind: `/home/seth/soggy': Permission denied You can send data to /dev/null using redirection. It's called null, and it's located in /dev, so it's often pronounced "devnull" by people who use it too frequently to say "slash dev slash null." Just as there are locations for standard in, standard out, and error, there's also a location for nowhere on the Linux filesystem. An introduction to programming with Bash.This command directs error messages to a file called output.log: $ ls /nope 2> output.log Sending data to /dev/null As long as you don't forget to end the clause with your end-of-file marker, it's an effective way to avoid unwieldy lists of echo or printf statements.Ī here-string is similar to a here-doc, but it consists of just one string (or several strings disguised as a single string with quotation marks): $ cat for the purposes of redirection. It can be useful, however, when a command expects a list of arguments, and you have those arguments in a file and want to quickly "copy and paste" them from the file into your terminal (except you don't actually want to copy and paste): $ sudo dnf install $( fooĪ here-doc is a common trick used by Bash scripters to dump several lines of text into a file or onto the screen. This is arguably less useful than redirecting output because many commands are already hard-coded to take input from an argument you provide. You can redirect input "into" a command, too. (In case you're wondering why you'd ever want to do that, it's for a sometimes-useful repercussion on file permissions.) Redirecting input You can use redirection for binary data: $ cat image.png > picture.png It doesn't have to be a text file, either. This is so versatile, in fact, that you can even use it to copy the contents of one file to another. You don't see the output of ls as you normally would, because the output is written to the list.txt file instead of your screen. The basics of redirection are simple: use some number of > characters to redirect output, and some number of list.txt You can see them in /dev: $ ls can't do much with them directly, but it's sometimes useful to think of them as meta-locations where you can send data. Standard in, standard out, and standard error exist as filesystem locations on Linux. Understanding that these data streams exist enables you to control where information goes when you're using a shell, such as Bash or Zsh. Input gets read from stdin (standard input, usually your keyboard or mouse), output goes to stdout (standard output, a text or data stream), and errors get sent to stderr. Technically, it happens inherently whenever you interact with a computer. Redirection of input and output is a natural function of any programming or scripting language.
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