| # Aliases | |
| Aliases in Nushell offer a way of doing a simple replacement of command calls (both external and internal commands). This allows you to create a shorthand name for a longer command, including its default arguments. | |
| For example, let's create an alias called `ll` which will expand to `ls -l`. | |
| ```nu | |
| > alias ll = ls -l | |
| ``` | |
| We can now call this alias: | |
| ```nu | |
| > ll | |
| ``` | |
| Once we do, it's as if we typed `ls -l`. This also allows us to pass in flags or positional parameters. For example, we can now also write: | |
| ```nu | |
| > ll -a | |
| ``` | |
| And get the equivalent to having typed `ls -l -a`. | |
| ## List all loaded aliases | |
| Your useable aliases can be seen in `scope aliases` and `help aliases`. | |
| ## Persisting | |
| To make your aliases persistent they must be added to your _config.nu_ file by running `config nu` to open an editor and inserting them, and then restarting nushell. | |
| e.g. with the above `ll` alias, you can add `alias ll = ls -l` anywhere in _config.nu_ | |
| ```nu | |
| $env.config = { | |
| # main configuration | |
| } | |
| alias ll = ls -l | |
| # some other config and script loading | |
| ``` | |
| ## Piping in aliases | |
| Note that `alias uuidgen = uuidgen | tr A-F a-f` (to make uuidgen on mac behave like linux) won't work. | |
| The solution is to define a command without parameters that calls the system program `uuidgen` via `^`. | |
| ```nu | |
| def uuidgen [] { ^uuidgen | tr A-F a-f } | |
| ``` | |
| See more in the [custom commands](custom_commands.md) section of this book. | |
| Or a more idiomatic example with nushell internal commands | |
| ```nu | |
| def lsg [] { ls | sort-by type name -i | grid -c | str trim } | |
| ``` | |
| displaying all listed files and folders in a grid. | |
| ## Replacing existing commands using aliases | |
| > Caution! When replacing commands it is best to "back up" the command first and avoid recursion error. | |
| How to back up a command like `ls`: | |
| ```nu | |
| alias core-ls = ls # This will create a new alias core-ls for ls | |
| ``` | |
| Now you can use `core-ls` as `ls` in your nu-programming. You will see further down how to use `core-ls`. | |
| The reason you need to use alias is because, unlike `def`, aliases are position-dependent. So, you need to "back up" the old command first with an alias, before re-defining it. | |
| If you do not backup the command and you replace the command using `def` you get a recursion error. | |
| ```nu | |
| def ls [] { ls }; ls # Do *NOT* do this! This will throw a recursion error | |
| #output: | |
| #Error: nu::shell::recursion_limit_reached | |
| # | |
| # × Recursion limit (50) reached | |
| # ╭─[C:\Users\zolodev\AppData\Roaming\nushell\config.nu:807:1] | |
| # 807 │ | |
| # 808 │ def ls [] { ls }; ls | |
| # · ───┬── | |
| # · ╰── This called itself too many times | |
| # ╰──── | |
| ``` | |
| The recommended way to replace an existing command is to shadow the command. | |
| Here is an example shadowing the `ls` command. | |
| ```nu | |
| # An escape hatch to have access to the original ls command | |
| alias core-ls = ls | |
| # Call the built-in ls command with a path parameter | |
| def old-ls [path] { | |
| core-ls $path | sort-by type name -i | |
| } | |
| # Shadow the ls command so that you always have the sort type you want | |
| def ls [path?] { | |
| if $path == null { | |
| old-ls . | |
| } else { | |
| old-ls $path | |
| } | |
| } | |
| ``` | |