We all learn new things over time as we use applications with a vast amount of possibilities. Of course, some of those things would have been so useful if we had known them earlier. Here are 10 command line tricks that I wish I had learned much sooner. Note: these tricks apply to bash, which is the default shell on most Linux systems. Solution: ensure your cursor is at the end of your current command shortcut: Ctrl+Epress Ctrl+U to get a clean line, type the other command you need to execute first, execute it, then press Ctrl+Y and voila. Your long command is back on the line. No mouse needed for copying, just quick hotkeys. The quickest way to retrieve and execute it is to press Ctrl+R and type a few characters that are part of your command. And, last but not least, you can still edit the command you found using Ctrl+R before hitting Enter; just press the right or left arrow to get out of the history search mode, and edit away. When working over an ssh connection, commands that take long to execute can seriously get in your way. Both annoyances melt away when you use screen. The screen command allows you to run multiple terminal sessions inside a single terminal session, and manage the multiple sessions using hotkeys. This will take quite long and block your terminal. However, if you press Ctrl+A, let go of the keys, and then press C, you will get a fresh new terminal ready to take commands. The sleep command on the other terminal keeps running without being interrupted. To cycle between the two open terminals, use Ctrl+A N for next and Ctrl+A P for previous remember to let go of all keys after pressing Ctrl+A. Finally, to shut down screen without interrupting the commands that are running, press Ctrl+A D for detach. To exit a screen session, just exit all terminals in it as you would normally exit terminals Ctrl+D. Whenever you want to execute a command on multiple files, or for every line of a certain file, xargs is the first tool to look at. This command does it for you in an instant. The null character is never used in filenames, while a newline may be, so it is safer to separate by null characters. It minds the limits the system imposes on the amount and size of command line arguments, and will run svn multiple times as necessary while still invoking it as few times as possible. Using xargs is safer and more versatile than using the -exec option of find. linux multiple commands per line For ultimate versatility, however, use the slightly less elegant for loop, which is described in the second part of this list. linux multiple commands per line Using bash as a simple calculator. Sometimes you need to quickly do a calculation that is too large or too important to do using your head. Fortunately, you can do basic calculations within bash itself. The syntax also supports showing the decimal equivalent of a hexadecimal or octal number. Using bc, you can perform floating point operations with any precision you like. The scale variable controls the amount of decimals behind the dot that are calculated. I used 12 here because kcalc uses that amount by default, but you can increase or decrease it as you like. It even supports more advanced mathematical functions, such as the arctangent or the natural logarithm. There also exist operations to strip from the back of the string useful for removing file extensionsto search and replace in a string and to extract substrings. To learn more about string manipulation, visit. Or, the other way around, sometimes you are in a certain network and you need unobstructed access to the internet, but some hyperactive firewall is in the way. If you have ssh access to a computer that does have the internet access you need, you can use it as an anonymous tunneling proxy without any additional tools. Just add the following option when you ssh into the server: ssh -D user remotehost The -D option tells ssh to set up a dynamic port forward on local port. I like to use port number 1337, but almost any port between 1024 and 65535 will do. This setting is usually found in the same place as the other options for using a web proxy. Ever wanted to diff the outputs of two commands quickly. It takes four lines, however. Using process substitution, we can do this is just a single line: diffgives the path of that file to cat, and cat reads the output of echo from that file. The shortened diff command above does the same, only for two slightly more complicated commands. This technique can be applied in any place where a temporary file is needed, but it does have a limitation. The temporary file can only be read once before it disappears. If you need multiple accesses to the output of a program, use an old-fashioned temporary file or see if you can use pipes instead. Thought you would only get 10 tricks. And, to take it even further, you can linux multiple commands per line bash on Windows by installing!.
