# Additional Topics ## Tab Completion Hitting `` autocompletes what you're typing, based on the names of the files and directories in your current directory. Hit `` constantly to make yourself more productive. ## Filename Wildcards Sometimes we want to refer to a bunch of similar files, to do this we can use wildcards. Think of wildcards as placeholders for any text. The most common wildcard to use is `*` usually along with a file extension. ``` ls -la *.txt ``` The above command lists all files that end in `.txt`, but begin with anything. ## History Lastly, there are a few different commands for checking your terminal's history. What have we been up to? Use the up and down arrow keys, or the `history` command. ``` history ``` ## Environment Variables Your current terminal session has variables called **environment variables**. There are really useful for storing commonly used commands and settings. Try typing `env` to view all of your environment variables. You can also set your own environment variables in your shell's configuration file `~/.zshrc`. Storing the variables in the configuration file will load them for every session. If you want to create a temporary environment variable, here's an example: ``` export MY_SETTING='subl .' ``` To access the variable: ``` $MY_SETTING ``` ## Getting Help For any command we discuss here, the command `man`, short for **manual**, will give a (hopefully) detailed explanation of that command. Sometimes that explanation will be too detailed for you. When you get lost in a man page and you want to understand it, start again from the beginning of of the **man page** and keep repeating. Hopefully you will get further into the page each time you read it. Many third party commands also accept the --help option, but not all, but if you get stuck it can be worth a try. Most of the commands covered in this lesson overview do not support this feature. However, commands like `git` do! ## Useful Links * [Terminal Cheat Sheet](https://github.com/0nn0/terminal-mac-cheatsheet) * You may want to start bookmarking this and other resources you find helpful * [Different Flavors of Shells](http://www.tutorialspoint.com/unix/unix-shell.htm) * You can try entering these shells by typing their names * **Example:** `bash` opens the bash shell. Type `exit` to exit the shell * [Command Line Crash Course](http://cli.learncodethehardway.org/book/) * A useful tutorial similar to ours, but with a few additional commands * [File Permissions](http://en.flossmanuals.net/command-line/permissions/) * [Shell Scripts](http://www.howtogeek.com/67469/the-beginners-guide-to-shell-scripting-the-basics/) * We won't cover this much, but there's a whole scripting language for running programs in the shell! Try going through this sometime to become a productivity mastermind.