# Shell history tips If you're a dev who is new to the terminal, or rarely uses it, you probably don't know much the shell's history and how to use it to your advantage. Time to change that by teaching you some tricks I use everyday. ## Hit ⌃+R to search the history Hey you, the dev hitting the (Up Arrow) key a hundred times to search for a command you typed yesterday, stop that. You’re just wasting your time! Instead, hit (Ctrl) + R and type keywords to search your history. (And nope, it’s not [Cmd] on macOS—it’s still ⌃.) It's your terminal's time machine. The more you use it, the faster it’ll be engrained in your muscle memory to the point you’ll never think of hitting ↑ anymore. Instead, let’s say you’re looking for the last `ls` command you typed, you’ll hit ⌃+R then `ls` and you’ll find it right away. The command history is a feature found in most shells enabled by default, including _Zsh_ and _Bash_. ## Command notes with `#`{:aria-label="Hash"} You typed a long complex command, maybe one that uses sed or awk or grep. You’d like to save it for later, but since it’s using a program you use often, you’re worried searching for it with ⌃+R won’t be enough to find it. You’ve probably did many trials and errors to come up with the correct command, and you don’t want to lose it and have to go through the process again. Here’s one thing you can do to help yourself. Once you’ve typed the correct command you want to save, add a comment at the end: ```sh echo hello-world | sed -E 's/-/_/g' # Convert all dashes to underscores ``` Like in shell scripts, the part of every line starting with a `#`—which is prefixed by a space if it’s not the first character of that line—is ignored. Meaning the above adds a comment to a command, like a note, which will be saved in history and is searching later. If you type the example above and do Ctrl+R then type “underscore,” that command will show up again. That’s much easier to find than having to go through a hundreds of `sed` commands you’ve tested before it. ## Prepare a command for later Extending the comment tip above, there are times you are writing a long command with dozens of arguments, but then you need to clear it because you just realised you need to run something else first. However, you don't want to lose what you just wrote! You may copy and paste the command out of your terminal into a text file or something. But there's a simpler way. Just go back to the beginning of the line, add a `#`{:aria-label="Hash"}, to turn the whole line into a comment that will be remembered—and be searchable—in your history: ```sh # ffmpeg -i input.mp4 -filter:v "crop=in_w:in_h-50,crop=ceil(in_w/2)*2:ceil(in_w/16*9/2)*2" # ^ The `#` in front saves the command as a comment in the history. ``` When you want to use that command, search for it with ⌃+R, go back to the beginning of the line, and remove the `#`{:aria-label="Hash"} and any leading space—because if you keep the space in, remember, the command will be excluded from the history—then run it! ## Repeat the last command with `!!`{:aria-label="Double Exclamation Mark"} Sometimes you wrote a long complicated command, but then you need to run it one more time with an extra argument or with `sudo`. Instead of searching for the command in the history and edit it, simply use `!!`{:aria-label="Double Exclamation Mark"}. That will get replaced by the previous command you ran: ```sh vim /etc/hosts sudo !! # Run the last command, `vim /etc/hosts`, with sudo. bundle show sinatra cd `!!` # Run `bundle show sinatra` again, but use its output with `cd`. ``` **Bonus:** For repeating the same command with `sudo`, you may also want to look into plugins available for your shell. For example, the `sudo` plugin for [_Oh My Zsh_](https://ohmyz.sh) lets you hit Esc to repeat the last command with `sudo`. ## Exclude from history with a space Keeping your commands in a history forever is great for later reference, but what if there are commands you don’t want to save? Maybe you’re inputting a command that has a secret key in it or some private details. Simple. Prefix your command with a blank space. If a line begins with a space (` `), it will act like your prompt’s incognito mode and will not save the command in history: ```sh # Command saved in history echo "I'm in your history" # Command not saved in history echo "I'm not in your history" # ^ Notice the blank space at the beginning. ``` However, that behaviour is set by default maybe only 95% of the time in every shell—test it first before you use it. If it’s not active, check your shell’s documentation on how to enable it. Also, keep in mind that any private information you type on the command line will likely be visible in the `ps` process listing while the command is running. The space prefix only affects history, not process listings. ## Select files with `fzf` This is not related to the history, but it's something that really falls in line with searching. [`fzf`](https://github.com/junegunn/fzf) is a command-line fuzzy finder. Once installed, while typing a command, it lets you search for files in the current directory by hitting ⌃+T. ## Better history with Atuin You can take your command history further by replacing it with [Atuin](https://atuin.sh). That tool imports your history from your favourite shell and replaces it to save any new command you’ll input. Everything is stored in a SQLite database and you can easily search through commands you’ve input for years. Atuin also lets you sync that database in their cloud, so you can use the same history on multiple machines. Although, I’m not fond of that solution, using it is up to you. You can also set up your own syncing server. Anyway, I hope these tips help. If anything, at least remember to use ⌃+R! ;)