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Notice that the initial ">" is numbered while the next isn't. That is because standard output is stream 1 along with the ">" divert supposes flow 1 if no number is given. To understand the workings of redirection, it is important to understand what sources of information your shell may redirect. In Linux there are three "streams" of data. The initial would be "standard input," numbered from the system as flow 0 (since computers count from 0). It is made up of instructions or the advice submitted to the shell for evaluation. Most of the time, this stems in the consumer typing things. Instead, we can use the "<" to redirect sorted versions of each file to "comm", that might look like this: $ find / -name wireless &> results.txt As an example, what if you wished to search your system for wireless port information that is accessible to consumers? For that, we could use the powerful "find" command. Redirecting Standard Error This is only a basic overview of how redirection in the shell works, but these building blocks are sufficient to allow possibilities. Like everything else about the terminal the best way to get a taste of the things it can do would be to try it out 3 Streams As you would imagine, it is the stream of data after doing some process, usually that the casing sparks. What if you wanted to save the results to their particular file, without cluttering your error document? Since streams can be redirected we can just put in our output redirection to the end of our control like so: $ mv date.txt trace1.txt Ultimately, in the Event You wanted All of the info from this command -- errors and successful finds -- hauled in the same place, you can redirect both flows to the Identical location using "&>" as follows: Ultimately, we returned data and can divert the stream of error to do mistakes, or things like error log files. This is helpful, by implementing an additional measure but we could build on it. Let's say you are trying to monitor the path your traffic takes over the Internet fluctuates from day to day. The "traceroute" command will tell us each router, including the nearest ones at the backbone of the Internet, that our connection travels through from source to destination, so the latter being a URL provided as a debate. Just like parentheses in math, the shell then proceeds with what is left and procedures orders in parentheses first. Here, the two documents are sorted and then fed into "comm", which then compares them and presents the results. $ date > date.txt Let us say you want to create a document that lists the time and date of today. Fortunately for us, there is a command that returns that info, aptly called "date". The info that that they process to shell output is usually returned by commands. To receive it into a file, we add ">" after the command and before the name of the destination document (using a space on link - Recommended Web page - each side). Ordinarily, when a non-root user runs "find" system-wide, it elevates standard output and standard error to the terminal, however there's generally more of the latter than former, making it hard to pick out the desired information. We can fix this Simply by redirecting standard error to a file with "2>" (because standard error is stream 2), and this leaves just standard output returned to the terminal window: With redirection, whatever file is specified following the ">" is overwritten, so unless you're certain that you won't shed anything significant, it is ideal to provide a fresh name, in the event a document with this name is going to be created. Let's call it "date.txt" (that the file extension following the period isn't important, but assists us humans with business). $ find / -name wireless two> denied.txt Now all we need to do is change the name of the document to something more descriptive, using the "mv" command with its original name as the primary argument and the new name as the next, like so: Redirecting Standard Output The final flow, "standard error," numbered flow 2, is comparable to standard output as it generally takes the form of data thrown into the terminal window. However, it is separate from output if desired, so that the flows can be handled. This is helpful when you've got a command working on lots of data in a complex functioning, and also you don't want errors and the data produced to have chucked in exactly the exact same file. Since we already have a document with a date inside, it would be sensible only to tack to the data from our scan to the end of that file ("date.txt"). To do this, we simply use two ">" characters next to each other (">>"). As you've probably guessed, redirection involves redirecting them from their destination to a different one and taking these flows. The terminal's command interpreter, for your shell, those symbols aren't wasted keys -- they are powerful operators that can link information together, divide it apart, plus much more. One of the simplest and most powerful shell surgeries is redirection. By using a "<" instead of ">", we can redirect standard input signal by simply substituting a file for this. $ comm <(kind list1.txt) <(kind list2.txt) There's a "sort" command, however although it will return a sorted listing to the terminal, and it won't permanently sort the listing, which places us back in square one. We can rescue the sorted version of each list to its own file using ">" and then run "comm", yet this approach will require two controls when we could accomplish the identical thing with you (and with no leftover files). You are likely at the point in which you need to start putting what you've learned if you have taken the time to get the hang of terminal basics. Sometimes issuing one at a time is enough, but there are instances when it may be tedious to enter command after command to carry out a simple task. The point where the additional symbols on your keyboard come in this is. Let us say you have two files, "list1.txt" and also "list2.txt", which each contain an unsorted list. There's some overlap, while every listing comprises items the other doesn't. We can find the traces which are in standard using the "comm" command, but only if the lists have been sorted. $ traceroute google.com >> date.txt