A shell exclamation mark is not for yelling. Be lazy | Hacker News Reader

A shell exclamation mark is not for yelling. Be lazy

refp.se

170 pointsrefp79 comments

Every time someone brings this up, I think "oh right, I could do that" and then immediately forget. Especially if you can type quickly, it's easier to just "drive straight ahead" with the command you want, than add another "mental branch" to interrupt the flow. For the same reason I'll often Ctrl+C and start again instead of trying to backspace and correct.

As an Emacs using degenerate, `M-.` is my friend. `!` is too awkward on the keyboard.

I guess you could map it to the right-hand M key?

Not while I've my keys mapped as the Lords of Lisp intended. Thumbs are always on the `Ctrl`s... https://en.wikipedia.org/wiki/Space-cadet_keyboard

As someone who can type rather quickly, I disagree. It can take some time to internalize, but once you do, it's much faster.

Same with Ctrl-C - once I got used to navigating by word instead of by character to correct things, it became much faster than starting over.

"sudo !!" is quite firmly burnt into my muscle memory, but the whole rest of the time when I type an exclamation mark I mean it literally, and I get annoyed when it turns into a syntax error of some variety.

Worse, the "press up-arrow to get the previous command, then fix the errors in it" flow is broken when an exclamation mark causes a syntax error.

I like to alias it to "please"

Oh, nice.

I alias'ed it to please as well. But because I use fish, I had to do this: alias please 'sudo (history -1)'

> For the same reason I'll often Ctrl+C and start again instead of trying to backspace and correct.

Try ctrl-x ctrl-e to edit the command in your choice of editor ($EDITOR).

Editing commands is not hard with a few keys. At least learn alt-b and alt-f to go a word back or forward. Often ctrl-left and ctrl-right will do the same thing easier (depends on your terminal). Ctrl-w deletes back to the previous space, alt-backspace and alt-d delete the previous and next word respectively. There are many more keys in the manual, but those cover most things.

Great advice. On the Mac, make sure to set up Alt/Option as "meta key".

So instead of just retyping the command (much less than 1s), I have to remember to open the editor, and then think of how to edit it, and then execute those steps? Hell no. At that point I'll have long lost my original train of thought. The original command, and at least the subsequent one, are already in my mind and can be output immediately. Any deviations from that plan are going to be much slower.

ctrl-x ctrl-e

Just thinking about that almost makes my fingers hurt. A chorded sequence of two keys, same side of the keyboard, nearly in a vertical line on the top and bottom row, is basically the slowest and most awkward possible combination to type.

Only because you’re typing it incorrectly. Use both hands. One presses the modifier, the other types the letter. That's why you have modifiers on both sides! C-x means to use your right hand to hold down control, while using your left to type the x.

X E is still a terribly slow sequence to type.

Not that slow; maybe you just need practice.

Alternatively just bind it to whatever key you prefer by editing your `~/.inputrc`. Add a line like this to it:

    "\C-e": edit-and-execute-command

and you will only have to type control-e to edit the current command. Don’t forget that `bind -P` will list all the current key bindings. It’s rarer, but you might also have some keys bound not to internal commands but to strings or external commands. You can list those with `bind -S` and `bind -X` respectively.

Also, don’t forget that lots of other things use readline too. You can use the same key bindings in many interactive environments, such as your favorite programming language’s REPL, your SQL prompt, calculators like bc or units, your favorite debugger, etc. If you come across a command environment that doesn’t use readline directly you can run it with rlwrap to remedy that. The more you use them the more places you will find where they are useful, and the more utility you will get out of them.

this is overkill and way slower for most short commands. And you still need to scroll to wherever you need to edit. doesn't save anything, really.

If you use vi or emacs you can edit directly using the bash/readline editor.

(Or if you use emacs, then you already have a full editor in your shell)

Decades ago, I was taught to use `!` and Co, by a Linux user who was fond of the `sudo !!` trick. Then I switched from this implicit interpolation to explicit shortcuts, and I'm glad I did.

As suggested in the FAQ at the bottom, instead of !… you can use ctrl-r. Or better, optionally type the first letters then alt-p or "up". It's more powerful and more extensible. Other shortcuts, like alt-., allow navigating into the past parameters.

With up, alt-p, alt-. and such, the command line displays the real command. The !… magic is more error-prone and ambiguous; with zsh, I'd suggest hitting TAB to expand the magic into a static text.

I would add other entries to the FAQ: When I enter `sudo !!` will it be stored unchanged in the shell history, or stored after interpolation of `!!`? When I start a command line with a space, so that zsh does not put it in the shell history, will !… also ignore that line? Is `!$` recursive?

Your questions would be a great addition to the FAQ, thank you!

> When I enter `sudo !!` will it be stored unchanged in the shell history, or stored after interpolation of `!!`?

event-designators themselves do not end up in history, it will be the expanded contents:

    $ echo "hello world"
    hello world
    $ echo !$:s/world/idoubtit/
    echo "hello idoubtit"
    hello idoubtit
    $ history
        1  echo "hello world"
        2  echo "hello idoubtit"
        3  history

The above is ironically enough quite annoying when writing a post about event-designators, as you'd want to reach for previous pre-interpolation commands.

> When I start a command line with a space, so that zsh does not put it in the shell history, will !… also ignore that line?

leading space to ignore adding things to the history is not default behavior, but event designators will still be able to capture their contents. Notice how "echo 321" is _not_ part of the history, but our usage of !$ is:

    % setopt HIST_IGNORE_SPACE
    % echo "abc"
    abc
    %  echo "321"
    321
    % echo last-argument-was !$
    echo last-argument-was "321"
    last-argument-was 321
    % history
    22092  setopt HIST_IGNORE_SPACE
    22093  echo "abc"
    22094  echo last-argument-was "321"

> Is `!$` recursive?

I think this is indirectly answered by the above, if not let me know and I will see if I can answer.

---

Will try to update the post within the next few hours with your additional questions — much much appreciate the feedback, and thanks for reading!

FAQ updated: https://refp.se/articles/your-shell-and-the-lazy-exclamation...

really appreciate the feedback, thanks a million!

IMO, !$ is most useful of them all (it is the one that gets replaced with the last argument of the last command).

!! you can do just as easily with up-arrow enter, which is just as quick. !ssh you can do with ctrl+r, which actually shows you what it's going to run and whether the last ssh is to where you think it is. sudo !! is up arrow, ctrl+a, 'sudo ', one more keystroke but it's natural if you know your readline. The rest are too complex and not worth learning. !$ is the sweet spot.

instead of !$, I use alt+. for the same reason `up` is preferable to `!!`.

!$:h is new to me. directory name of last argument is nice. I can imagine reaching for that. paired with alt-^ to replace the magic with the actual expanded text before hitting enter

thank you for alerting me to the presence of Alt+.

No idea how I've missed this for as long as I have

>!! you can do just as easily with up-arrow enter

  sudo !!

Ctrl-P-A then typing sudo is just as easy, it's simply up to preference

`IMO, !$ is most useful of them all (it is the one that gets replaced with the last argument of the last command).`

I've been liking Esc+. for this. It doesn't usually work in browser sessions though, have to do Ctrl+[+. which is a strange feeling 3 finger salute. For some reason I'm able to remember that one rather than !$

Edit: apparently Alt+. does the same, wow.

This is for teletypewriters. For those of us with interactive electronic video displays, we can use up-arrow to recall the last command or Ctrl-R to search history, then edit the recalled command.

I appreciate the true snark of this :)

And for editing that command line... I know a lot of people who know about Ctrl-a, Ctrl-e, Ctrl-k, but still hold down the left arrow key or delete key a lot to edit things in the middle.

Those people want to use:

    Alt-f    move cursor forward one word
    Alt-b    move cursor back one word
    Alt-d    delete to the end of the next word
    Alt-Del  delete backwards to the start of the previous word

    Ctrl-_   undo

Here's a cheatsheet: https://readline.kablamo.org/emacs.html

Ctrl-arrowkeys also works for word cursor movement in regular bash, and alt-backspace deletes a word.

Those people are fine just using arrows and backspace, as it isn't worth it to min-max this. I don't want to learn/use Emacs, this doesn't even work on macOS, and Ctrl+A interferes with my tmux keybind. This is why vi keybinds are nice in shells, but... defaults matter.

I haven't decided yet if I want to use NFS to malware my configs, or git. I think git is more flexible, but I don't want my configs in a public git.

Either way, I use atuin a lot, and before that history | fzf. Which is bound to ctrl+r for me. But again... not by default.

Rather than a sense of "cool" or "useful" somehow I end up just feeling despair at how organically convoluted it is to determine what something on a command-line really does. To be fair, I've always been biased towards "only the simplest scripts should be in shell languages."

This also adds an intriguing new dimensions to reviewing/verifying shell commands as benign and correct... How long until LLMs start (ab)using the trick in little requests they want me to approve?

man bash. That's the secret. man bash.

The cool thing about programming languages like Ruby is that they’re very conducive to one-liners. You can use them to generate bash statements that you can then pipe back to bash. `ls | ruby -nle 'puts "mv #{$_} #{$_.gsub(/_/, ".")}"' | bash` is a pattern I use all the time, for example. Easy way of generating complex bash statements without having to bother with the bash man page.

Do you need to pipe the ruby output to bash? Ruby could just run the mv directly by wrapping in backticks instead of quotes.

Running it through the pipe lets you preview the command first and make sure it actually looks correct. Then you just re-run the command and append the bash pipe.

ls | while read filename; do mv "$filename" "$(echo "$filename" | sed "s/_/./g")" || break; done

I think there's a variable expansion syntax that does replacement, but I haven't learned it so I use sed.

I find that piping to a while loop is often simpler and more flexible than something like you've written, but maybe not in this specific case with the weird string replacement syntax. However, mine doesn't have a command injection vulnerability (that I know of).

A real scripting language can also do this easily:

for f in os.listdir("."): os.rename(f, f.replace("_","."))

Sometimes I'm tempted to make Python my shell. The fewer different syntaxes you need to learn for the same basic operations, the better!

If you want to use ruby then just use ruby? That is a very fragile way to use bash that could easily lead to bad things.

Seems to be the flavour of the day :)

Maybe it's a bit like current C++ language spec:

There's enough complexity in the language spec that most people stick with a (fairly shared) subset.

Bash can be very powerful, but IMHO there's a certain point where I find it saner to accomplish the same thing via Python.

I think you are very much on point, I can definitely relate to the complexity of C++ turning it both into a wonderful adventure, but also a swamp where every step feels uncertain.

Disclaimer; author of this post, and also https://refp.se/articles/non-constant-constant-expressions and related post in that series.

Everyone need be aware, bash uses emac extensions by default. As I refuse to use emacs, I therefore refuse to use these extensions in bash!

In as most sensible people use vi, don't taint yourself by touching this foul and evil emacs magic. Being known as an emacs user could cost you a job, shorten your career, or even cause rifts with family and friends.

Instead my friends, if you must use such bash shenanigans, switch it to vi extensions. You'll feel better about yourself, stand taller, and be a better human being as a result.

Be safe.

Well, Emacs shenanigans are why I use Bash. Also, I last had a day job five years ago, I don't have anything that looks like a career, and well you're right about some of the family and friends.

You are a soothsayer!

It’s a funny comment, but it’s also sort of true. Back in the stone ages I had to go from Solaris to sunOS to QNX to Unixware to HPUX to Linux to BSD (maybe freeBSD was in there too) and many others that I can’t remember. Oh yea, Irix, too. This is all in a 2 year period. Vi was the only editor that was on all of these machines so I (to this day) could never be bothered to learn anything else.

> alt-. is great for what it is designed to do, iterating over the previous "last arguments" of your shell history. It's great at doing that, but it is also limited to doing just that one thing.

No, it isn't limited to just that. Alt-0 alt-. will give you the zeroth "argument" (the program), alt-1 alt-. will get you the next (the program's first argument), etc. Negative arguments count back from the end: alt-- 1 alt-. will get you the argument before the last one (note that alt is held for the "-" but not the digit).

When you do use event designators, ctrl-alt-e (or alt-^) is critical. It expands all the ! codes inline to what they refer to, so you can see what you're doing before you hit enter, and as you're constructing the command too.

Author here, thanks for reading and taking time to reply!

---

You are very much correct that `Alt-.` with modifiers can do more than what has been described, it is however important to note that the behavior of `Alt-<key>` changes heavily both between zsh and bash, but also between `vi-mode` and `emacs-mode`.

For instance, zsh will switch to `vi-mode` depending on env variables such as `$EDITOR`, making `Alt-<key>` unavailable in that regard.

---

It's also worth noting that `ctrl-alt-e` is _not_ a zsh default, though it is a fair point that it could have been added in the below linked section:

https://refp.se/articles/your-shell-and-the-lazy-exclamation...

For what it's worth, I had troubles finding a proper scope for the article contents — and with that the lines became a bit blurry in terms of what to include, and what not to include.

---

I really appreciate constructive comments like yours, and hope it together with the article can help future shell ninjas!

Also, on the note of "you can do everything with Alt-<key>", I'd like to highlight that modifiers such as `:h` (directory part), `:t` (filename), and `:r` (strip extension) etc., is what the article was aimed at when saying you can do more with event-designators.

What you can do with what is always hard to answer given that all roads lead to Rome, though some roads have more turns than others.

i use `shopt -s histverify` instead of ctrl-alt-e.

This article taught me about alt-. and it's probably going to become my new favorite fish shortcut: if I type a portion of a word (for example an ssh hostname), hitting alt-. searches all previous arguments and autofills the entire username+hostname at that position. Seems much more powerful than bash's implementation. (and allows you to go forward/backward with alt+arrow keys if you overshoot it)

Instead of alt-^, I set “magic-space” in `.inputrc`.

This will expand the event designator after you type space to end it. So you type “!” “$” “space” and the designated argument expands in-place.

I got used to doing this over many many years with the tcsh shell. I switched to Fish recently and I continue to be annoyed by its refusal to implement this feature. Yes, I tried using all the newfangled history-search thingamajigs. They all kind of work, and they all have their issues. But the !, together with in-place expansion, is something I still dearly miss.

sigh The usability of ! versus Ctrl+R in a shell is pretty much the same as the usability of ed versus vi, or moving files around using cp/mv versus using Midnight Commander or the like: in the first case, you have to accurately remember the past (which for many people is pretty difficult); in the second case, you don't have to, because you always have an immediate view of the state of the system and the preview of the effect you're about to incur.

And yeah, I've done editing with ed; it definitely beats "cat >file.txt" and copying parts around with head/tail and retyping the corrections manually, sure, and it works in every environment that can take line-oriented input from the user (so, literally everywhere), but that's about as much praise as I can give it.

> in the first case, you have to accurately remember the past

Right, as a matter of (relatively trivial) cybernetics between man and machine, it rests on the weaker parts of the human.

TBF, it'd make a lot more sense if every command on screen (or given the timescale perhaps teletype paper prinout) was already labeled with the necessary number.

You can just add something like (\\!) in your PS1 and get just that.

PS1="(\\!) \[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ "

as a full working example

> you have to accurately remember the past

From personal experience I rarely reach for event-designators beyond the current viewport of the terminal. Referring to a command beyond that is, as you very much correctly point out, an easy way to get behavior you don't want. However, if you are always referring to things that are near-memory or even still directly visible in your terminal buffer — the gun-to-foot ratio becomes manageable. I use many (many) of these daily without issues, but it does require some additional discipline.

Also, and this I find important to note, `!!` and `!$` sit outside of the memory argument as they always refer to the last command and last-command's last-argument respectively — as such there shouldn't be any recall related problems (unless you are context switching and come back to a shell in a state you don't remember).

A common occurrence when my posts acquire attention is that I retroactively realize that some things could have been conveyed better; I read every comment and yours is a blessing in disguise to improve future writing.

Thanks for reading the article, and thanks for indirectly making me a better writer!

---

EDIT:

by the way, for what it's worth, the below linked section describes how to effectively explicitly confirm what you would run as a safety measure if unsure:

https://refp.se/articles/your-shell-and-the-lazy-exclamation...

Frankly,

    !-2 && !!

and its variations (like '!-2 | !!') is pretty much the most use I've gotten out of this feature.

The above is a useful idiom that has a somewhat different feel than using !$, etc. Construction versus surgery.

! calls are vital for your sanity if you ever do remote support

trying to write shell commands on a hypervisor console window within a remote session on a jump box is excruciatingly laggy and annoying, and that's assuming your remote session connection to the client is behaving well in the first place

I have a script that does virsh send-key of whatever I need to send. In my specific case the motivation was the mismatch between my keyboard layout and the keyboard in the VMs, so I couldn't send M-# or even C-... into the VNC console.

I'm way too paranoid to ever use "!". I want to see the command I'm sending.

I'm much too lazy to memorise what all of these do, I'd rather just use fish wherever I can. Some combination of typing, arrow keys, and alt+arrow keys is always enough for me to find that thing I want to avoid fully retyping.

P.S. The alt+s shortcut is much quicker than writing sudo !!

I’ve been burnt before using ! and forgetting what command I typed previously, thus invoking the wrong command line.

!! is handy for the sudo example, but beyond that, I tend to prefer pressing the up arrow to cycle through the history rather than picking the first item. Eg:

  !ssh

  ssh[up]

It’s the same number of key strokes but less error prone

Agreed. I especially cringed at the author's example of mixing that with "sudo".

the "mixing of sudo"-example is using `!!`, which as explained is the immediately previous command, a little confused how that translates to the "execute command somewhere in the history" argument?

I suppose it depends on the kinds of mistakes to which one is prone.

That's mixing human memory with root access. Worse than AI :) I have lost more to mistakes than bugs over 30 years.

Worth noting that `ssh[up]` isn't available by default in bash nor zsh — though it wouldn't surprise me if helpers such as oh-my-zsh enables it for you. `ssh[up]` is certainly an awesome feature — though (perhaps sadly) not default behavior.

> I've been burnt before using ! and forgetting what command I typed previously

If you want to make sure you do not execute commands you did not intend to, the section linked below is a great start:

- https://refp.se/articles/your-shell-and-the-lazy-exclamation...

You may also look into `magic-space` which makes the expansion of event-designators happen inline, I thought about including it but the article felt long even without it.

Thanks for reading the article, I hope it was a worthwhile read even with alternate workflows elsewhere!

Thanks for the tips. These days I don’t use sh derivatives as my primary shell and the shell I do use has a few features to make command search more ergonomic and safer. But these are useful tips nonetheless

    bind space:magic-space

Or alt-^ to do it without any configuration.

If you find this interesting, don't wait for a random blogpost to appear by chance on HN, go read some manage today!

i love the mkdir example, so i’m going to exercise that muscle and see where it goes

and yeah ^r works, though i often type a few chars and ^p till i get the match. history-search-backward in your inputrc, iirc

edit: on a computer now :) my `if emacs` block, allowing arrows or ^n/^p to run through history. so for e.g., type "tar" and now as you shift through history with :binding:, it only shows history that began with "tar"

    $if mode=emacs
    "\e[A": history-search-backward
    "\e[B": history-search-forward
    "\C-p": history-search-backward
    "\C-n": history-search-forward
    ...
    $endif

That one was always worth its own function for me.

``` mkcd() { mkdir -p -- "$*" && cd -- "$*" } ```

> who haven't wished they could edit their long commands in an editor rather than in the shell?

That's called a shell script. I don't know what others thresholds are but mine is about three pipelines deep(or 80 characters whatever comes first) and I am going to write that son of a gun as a script. Mainly to have something named in the filesystem I can edit, same with my sql queries, I have a whole directory of long awkward mostly one off queries, psql has the \e command which helps but again I would rather have something named.

If you really want to be lazy, use a terminal file manager (I prefer lf[0]) it helps avoiding the cd && ls dance. That way, your history only contains commands you actually would want to rerun.

0: https://github.com/gokcehan/lf

> That way, your history only contains commands you actually would want to rerun.

just turn on the thing where a leading space doesn't commit to history and you can do this already.

Not knowing what command you are doing before you submit it is poor design. There are alternative ways to access old commands where you can see the actual command you are about to run before you submit it. The physical teletype era is over.

You can add :p to print the command.

> Not knowing what command you are doing before you submit it is poor design.

For this reason I recommend avoiding using history expansion features with any commands in history that might destructively modify file contents, such as `find ... -delete` in GNU find.

In the default Bash Emacs readline bindings, you can type Alt/Meta-^ to expand history on the current line without executing. You can also set `shopt -s histverify` to expand the history substitution on the following line after pressing enter/submitting the history substitution and it also does not execute the command.

Very annoying prose.

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