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Notice that the first ">" is plotted while the second isn't. That is because standard output is flow 1 and also the ">" divert assumes flow 1 if no number is provided. To comprehend the workings of redirection, it is important to understand what resources of information your shell could redirect. In Linux there are three "streams" of data. It consists of the information or directions . Most of the moment, this comes from the consumer typing things into the terminal window. Rather, we can use the "<" to divert sorted variations of every file to "comm", that might look like that: No find / -name wireless &> results.txt As an example, suppose that you wanted to search your entire system for wireless port information that is available to non-root consumers? For this, we could use the powerful "find" command. Redirecting Standard Error These building blocks are enough to allow possibilities, although this is only a basic outline of redirection in the shell works. Like everything else about the terminal, However, the best way to get a taste of what it can do is to try it out to yourself 3 Streams It's the flow of data after performing some procedure, usually that the shell outputs as you could imagine. Imagine if you wanted to conserve the results to their own record, without cluttering your error file? We can put in our Normal output redirection towards the finish of our command like this since streams can be redirected individually: $ mv date.txt trace1.txt Finally, in Case You wanted All of the information from this control -- errors and successful finds -- hauled in the same place, you could redirect both streams to the Identical location using "&>" as follows: We can divert the flow of mistake to do things such as error log files, or errors and returned information. This is not terribly useful, by executing another measure but we can build on it. Let's say you are attempting to track the route your traffic takes on the Internet fluctuates from day to day. The "traceroute" command will inform us each router, for instance, infrastructural ones in the backbone of the Internet, that our link goes through from origin to destination, and the latter being a URL provided as a debate. Much like parentheses in math, with what is left, the shell procedures orders in parentheses and then proceeds. Here, the two files have been piled and then fed into "comm", which then contrasts them and presents the results. $ date > date.txt Let's say you want to create a record that lists the date and time of today. The info that that they process to shell output is usually returned by commands. To receive it in a file, we insert ">" after the command and before the name of the destination document (using a space on either side). Normally, when a non-root user conducts "find" system-wide, it disturbs standard output and standard error to the terminal, however there's usually more of the latter than prior, making it difficult to find out the desired information. We can content (site) fix this Simply by redirecting standard error to a file with "2>" (because regular error is flow 2), which leaves just normal output returned to the terminal window: With redirection, whatever file is specified after the ">" is overwritten, so unless you're confident that you won't lose anything significant, it's best to provide a fresh name, in which instance a document with that name is going to be generated. Let us call it "date.txt" (the file extension after the period typically is not significant, but assists us humans with organization). We all Will Need to do is change the title of the file to a more descriptive, using the "mv" command using its original name as the primary argument and the new name since the second, like so: Redirecting Standard Output The concluding stream, "standard error," numbered flow 2, is similar to standard output since it generally takes the kind of data dumped into the terminal window. But, it is conceptually different from output if desired, so that the flows can be handled independently. This is helpful once you have a command working on plenty of information in a complex operation, and you also do not want the data and errors produced to have dumped in exactly the exact same file. Because we already have a record with a date in it, it would be sensible just to tack on the information from our scanning into the end of that record ("date.txt"). Our brand new redirection looks like this: As you have probably guessed, redirection entails redirecting them and carrying these streams. This is accomplished using the ">" and "<" characters in a variety of combinations, depending on the place you need your information to end up. For the shell, the command interpreter of the terminal, these symbols aren't wasted keys -- they are strong operators that could link information together, divide it. One of the simplest and shell surgeries is redirection. By employing a "<" instead of ">", we can redirect standard input signal by substituting a document for it. $ comm <(sort list1.txt) <(sort list2.txt) There is a "sort" command, however even though it is going to return a sorted listing to the terminal, and it won't permanently sort the listing, which places us back in square one. We can save the sorted version of each set to its own document with ">" and then conduct "comm", yet this approach would require two controls when we could achieve the identical thing with you (and with no leftover files). If you've taken the opportunity to get the hang of terminal basics, you are probably at the point where you wish to start putting together what you've learned. There are cases when it may be tedious to get into command after control to perform a simple task, although sometimes issuing orders one at a time is sufficient. Where the extra symbols on your keyboard come in, this is. Let's say that you have two documents, "list1.txt" and "list2.txt", which each comprise an unsorted list. There is some overlap, while every list contains things the other does not. We can discover the traces which are in standard with the "comm" command, however, only as long as the lists have been sorted. $ traceroute google.com >> date.txt