diff --git a/sources/tech/20191002 7 Bash history shortcuts you will actually use.md b/sources/tech/20191002 7 Bash history shortcuts you will actually use.md new file mode 100644 index 0000000000..d2cd9c1906 --- /dev/null +++ b/sources/tech/20191002 7 Bash history shortcuts you will actually use.md @@ -0,0 +1,236 @@ +[#]: collector: (lujun9972) +[#]: translator: ( ) +[#]: reviewer: ( ) +[#]: publisher: ( ) +[#]: url: ( ) +[#]: subject: (7 Bash history shortcuts you will actually use) +[#]: via: (https://opensource.com/article/19/10/bash-history-shortcuts) +[#]: author: (Ian Miell https://opensource.com/users/ianmiell) + +7 Bash history shortcuts you will actually use +====== +Save time on the command line with these essential Bash shortcuts. +![Command line prompt][1] + +Most guides to Bash history shortcuts exhaustively list every single one available. The problem with that is I would use a shortcut once, then glaze over as I tried out all the possibilities. Then I'd move onto my working day and completely forget them, retaining only the well-known [**!!** trick][2] I learned when I first started using Bash. + +So most of them were never committed to memory. + +This article outlines the shortcuts I _actually use_ every day. It is based on some of the contents of my book, [_Learn Bash the hard way_][3]; (you can read a [preview][4] of it to learn more). + +When people see me use these shortcuts, they often ask me, "What did you do there!?" There's minimal effort or intelligence required, but to really learn them, I recommend using one each day for a week, then moving to the next one. It's worth taking your time to get them under your fingers, as the time you save will be significant in the long run. + +### 1\. The "last argument" one: !$ + +If you only take one shortcut from this article, make it this one. It substitutes in the last argument of the last command into your line. + +Consider this scenario: + + +``` +$ mv /path/to/wrongfile /some/other/place +mv: cannot stat '/path/to/wrongfile': No such file or directory +``` + +Ach, I put the **wrongfile** filename in my command. I should have put **rightfile** instead. + +You might decide to retype the last command and replace wrongfile with rightfile completely. Instead, you can type: + + +``` +$ mv /path/to/rightfile !$ +mv /path/to/rightfile /some/other/place +``` + +and the command will work. + +There are other ways to achieve the same thing in Bash with shortcuts, but this trick of reusing the last argument of the last command is one I use the most. + +### 2\. The "_n_th argument" one: !:2 + +Ever done anything like this? + + +``` +$ tar -cvf afolder afolder.tar +tar: failed to open +``` + +Like many others, I get the arguments to **tar** (and **ln**) wrong more often than I would like to admit. + +[![xkcd comic][5]][6] + +When you mix up arguments like that, you can run: + + +``` +$ !:0 !:1 !:3 !:2 +tar -cvf afolder.tar afolder +``` + +and your reputation will be saved. + +The last command's items are zero-indexed and can be substituted in with the number after the **!:**. + +Obviously, you can also use this to reuse specific arguments from the last command rather than all of them. + +### 3\. The "all the arguments" one: !:1-$ + +Imagine I run a command like: + + +``` +`$ grep '(ping|pong)' afile` +``` + +The arguments are correct; however, I want to match **ping** or **pong** in a file, but I used **grep** rather than **egrep**. + +I start typing **egrep**, but I don't want to retype the other arguments. So I can use the **!:1$** shortcut to ask for all the arguments to the previous command from the second one (remember they’re zero-indexed) to the last one (represented by the **$** sign). + + +``` +$ egrep !:1-$ +egrep '(ping|pong)' afile +ping +``` + +You don't need to pick **1-$**; you can pick a subset like **1-2** or **3-9** (if you had that many arguments in the previous command). + +### 4\. The "last but _n_" one: !-2:$ + +The shortcuts above are great when I know immediately how to correct my last command, but often I run commands _after_ the original one, which means that the last command is no longer the one I want to reference. + +For example, using the **mv** example from before, if I follow up my mistake with an **ls** check of the folder's contents: + + +``` +$ mv /path/to/wrongfile /some/other/place +mv: cannot stat '/path/to/wrongfile': No such file or directory +$ ls /path/to/ +rightfile +``` + +I can no longer use the **!$** shortcut. + +In these cases, I can insert a **-_n_:** (where _**n**_ is the number of commands to go back in the history) after the **!** to grab the last argument from an older command: + + +``` +$ mv /path/to/rightfile !-2:$ +mv /path/to/rightfile /some/other/place +``` + +Again, once you learn it, you may be surprised at how often you need it. + +### 5\. The "get me the folder" one: !$:h + +This one looks less promising on the face of it, but I use it dozens of times daily. + +Imagine I run a command like this: + + +``` +$ tar -cvf system.tar /etc/system + tar: /etc/system: Cannot stat: No such file or directory + tar: Error exit delayed from previous errors. +``` + +The first thing I might want to do is go to the **/etc** folder to see what's in there and work out what I've done wrong. + +I can do this at a stroke with: + + +``` +$ cd !$:h +cd /etc +``` + +This one says: "Get the last argument to the last command (**/etc/system**) and take off its last filename component, leaving only the **/etc**." + +### 6\. The "the current line" one: !#:1 + +For years, I occasionally wondered if I could reference an argument on the current line before finally looking it up and learning it. I wish I'd done so a long time ago. I most commonly use it to make backup files: + + +``` +$ cp /path/to/some/file !#:1.bak +cp /path/to/some/file /path/to/some/file.bak +``` + +but once under the fingers, it can be a very quick alternative to … + +### 7\. The "search and replace" one: !!:gs + +This one searches across the referenced command and replaces what's in the first two **/** characters with what's in the second two. + +Say I want to tell the world that my **s** key does not work and outputs **f** instead: + + +``` +$ echo my f key doef not work +my f key doef not work +``` + +Then I realize that I was just hitting the **f** key by accident. To replace all the **f**s with **s**es, I can type: + + +``` +$ !!:gs/f /s / +echo my s key does not work +my s key does not work +``` + +It doesn't work only on single characters; I can replace words or sentences, too: + + +``` +$ !!:gs/does/did/ +echo my s key did not work +my s key did not work +``` + +### Test them out + +Just to show you how these shortcuts can be combined, can you work out what these toenail clippings will output? + + +``` +$ ping !#:0:gs/i/o +$ vi /tmp/!:0.txt +$ ls !$:h +$ cd !-2:h +$ touch !$!-3:$ !! !$.txt +$ cat !:1-$ +``` + +### **Conclusion** + +Bash can be an elegant source of shortcuts for the day-to-day command-line user. While there are thousands of tips and tricks to learn, these are my favorites that I frequently put to use. + +If you want to dive even deeper into all that Bash can teach you, pick up my book, [_Learn Bash the hard way_][3] or check out my online course, [Master the Bash shell][7]. + +* * * + +_This article was originally posted on Ian's blog, [Zwischenzugs.com][8], and is reused with permission._ + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/19/10/bash-history-shortcuts + +作者:[Ian Miell][a] +选题:[lujun9972][b] +译者:[译者ID](https://github.com/译者ID) +校对:[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译,[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/ianmiell +[b]: https://github.com/lujun9972 +[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/command_line_prompt.png?itok=wbGiJ_yg (Command line prompt) +[2]: https://opensource.com/article/18/5/bash-tricks +[3]: https://leanpub.com/learnbashthehardway +[4]: https://leanpub.com/learnbashthehardway/read_sample +[5]: https://opensource.com/sites/default/files/uploads/tar_2x.png (xkcd comic) +[6]: https://xkcd.com/1168/ +[7]: https://www.educative.io/courses/master-the-bash-shell +[8]: https://zwischenzugs.com/2019/08/25/seven-god-like-bash-history-shortcuts-you-will-actually-use/