Stephen Royle

There are a few one-liners that I use in the shell to do some really
nifty stuff. I struggle to quickly find and reuse these and asked for a
solution on Mastodon.

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A handy one-liner might be something like (taken from
[here](https://quantixed.org/2021/11/20/convertible-using-ffmpeg-to-convert-audio-files/){data-type="post"
data-id="2508"}):

::: {.wp-block-syntaxhighlighter-code}
``` {.brush: .bash; .title: .; .notranslate title=""}
find . -iname '*.flac' -exec bash -c 'D=$(dirname "{}"); B=$(basename "{}"); mkdir "$D/mp3/"; ffmpeg -i "{}" -ab 320k -map_metadata 0 -id3v2_version 3 "$D/mp3/${B%.*}.mp3"' \;\n
```
:::

This converts all the flac files in subfolders into mp3 files.
Obviously, we don't want to rekey this. And maybe it's called once a
week, with a lot of history in-between. How do we quickly find and reuse
this handy one-liner?

To recap: to find a previously used command it's possible to:

- use the up arrow to find the command. This is great if it was the last
  one or two, not so great if it was 15 lines ago
- call `history 1` find the line that is needed and then do `!500` for
  line 500. Works but is a bit clunky
- it's more efficient to do `history 1 | grep yout` or something to find
  only the lines that feature `youtube-dl` commands. But still not ideal
- It's possible to do ctrl + r and type in `yout` or something to find a
  previously line but I find this hard to use.
- Store useful commands somewhere. I have Notable set up, in which I
  record all kinds of stuff including one-liners. I have handy code
  written in all kinds of places (gists, ELN, this website etc.). It
  gets hard to remember what is where, so I wanted a better solution.

I should say I am using terminal on macOS with zsh as the shell.

## The responses {#the-responses .wp-block-heading}

I got some very useful replies to explore:

- auto-complete plug-in for zsh (suggested by Andrew)
- [espanso](https://espanso.org) (suggested by Tom Stafford)
- alias and functions (Hal Pomeranz) and a slightly more complex
  implementation of these (by Will Palmer)

I liked the look of espanso as a system-wide way of expanding text. It
seems very useful, beyond the terminal, so I set it aside for now.

I first tried this [zsh auto-complete
plug-in](https://github.com/marlonrichert/zsh-autocomplete). It is
actively maintained on GitHub and was simple to install. As described it
shows recently-used commands and is great for suggesting commands and
directories etc. Unfortunately, I found that it would cause terminal to
lock up. This was annoying because I lost my immediate history in the
lock-up. It sped up the process of locating one-liners for sure, but it
was still a little cumbersome. I uninstalled it and decided to look at
aliases and shortcuts.

## Aliases and functions {#aliases-and-functions .wp-block-heading}

OK, so these were not exactly new to me, but I hadn't been bothered to
set them up. So here's how I did it, if anyone wants to try.

An **alias** might be something like `ytd` instead of typing
`youtube-dl`.

A **function** is something more like a chunk of code, where you would
want to set some parameters via arguments.

Thinking about the one-liner example above, should it be an alias or a
function? It's arguable, but let's call it an **alias**.

Now, both aliases and functions can go directly into the `.zshrc` file.
But for tidiness it's best to put them into a distinct file and get
`.zshrc` to initialise that file when the shell starts.

### Edit .zshrc {#edit-.zshrc .wp-block-heading}

In home, open `.zshrc` with your favourite editor e.g.

::: {.wp-block-syntaxhighlighter-code}
``` {.brush: .bash; .title: .; .notranslate title=""}
nano .zshrc
```
:::

Then add the following to the file:

::: {.wp-block-syntaxhighlighter-code}
``` {.brush: .plain; .title: .; .notranslate title=""}
# Alias definitions

if [ -f ~/.zsh_aliases ]; then
    . ~/.zsh_aliases
fi
```
:::

This basically says, if there is a file called `.zsh_aliases` in home,
then load it. Save `.zshrc` by ctrl + x and y.

So now, let's make that file and edit it.

### Make .zsh_aliases file {#make-.zsh_aliases-file .wp-block-heading}

::: {.wp-block-syntaxhighlighter-code}
``` {.brush: .bash; .title: .; .notranslate title=""}
touch .zsh_aliases
nano .zsh_aliases
```
:::

In here, you can list as many aliases as you like. They take the form

::: {.wp-block-syntaxhighlighter-code}
``` {.brush: .plain; .title: .; .notranslate title=""}
alias name="oneliner"
```
:::

So for example, you might add:

::: {.wp-block-syntaxhighlighter-code}
``` {.brush: .plain; .title: .; .notranslate title=""}
alias hg="history 1 | grep yout"
```
:::

And this would allow you to type `hg` on the command line to search for
lines in the history that feature the string `yout`. This is not very
useful, so let's look at our previous one-liner.

::: {.wp-block-syntaxhighlighter-code}
``` {.brush: .bash; .title: .; .notranslate title=""}
find . -iname '*.flac' -exec bash -c 'D=$(dirname "{}"); B=$(basename "{}"); mkdir "$D/mp3/"; ffmpeg -i "{}" -ab 320k -map_metadata 0 -id3v2_version 3 "$D/mp3/${B%.*}.mp3"' \;\n
```
:::

To add this, we'd need to add:

::: {.wp-block-syntaxhighlighter-code}
``` {.brush: .plain; .title: .; .notranslate title=""}
alias flac2mp3="find . -iname '*.flac' -exec bash -c 'D=\$(dirname \"{}\"); B=\$(basename \"{}\"); mkdir \"\$D/mp3/\"; ffmpeg -i \"{}\" -ab 320k -map_metadata 0 -id3v2_version 3 \"\$D/mp3/\${B%.*}.mp3\"' \;\n"
```
:::

The thing to note here is that the original one-liner has a mix of
single and double quotes, and we need to enclose all of that in quotes
(either single of double). So we can use single quotes within a
double-quoted one-liner, but if we have double-quotes they need escaping
with a backslash. In addition, the `$` character also needs escaping.

Once you have added all the aliases you need, simply save and exit.
Remember that they won't get loaded until you rerun `.zshrc` once more,
which can be invoked by simply closing and reopening the terminal.

Now we can run this one-liner by simply typing:

::: {.wp-block-syntaxhighlighter-code}
``` {.brush: .bash; .title: .; .notranslate title=""}
flac2mp3
```
:::

To add **functions**, you can simply add another if statement to your
`.zshrc` file and make another file called `.zsh_functions` and put them
there.

*Thanks to everyone who replied on Mastodon, for their suggestions.*

---

The post title comes from "Over and Over" by The Beat from their 1981 LP
"Wha'ppen?". Did you think I was going to say: by Hot Chip?


There are a few one-liners that I use in the shell to do some really nifty stuff. I struggle to quickly find and reuse these and asked for a solution on Mastodon.

Messaggi di Rogue Scholar

Over and Over: quick ways to reuse handy shell one-liners