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自动选题: 20191002 7 Bash history shortcuts you will actually use

sources/tech/20191002 7 Bash history shortcuts you will actually use.md

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+[#]: 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/