def-env for core

Define a custom command, which participates in the caller environment

Signature

> def-env (def_name) (params) (block)

Parameters

  • def_name: definition name
  • params: parameters
  • block: body of the definition

Notes

This command is a parser keyword. For details, check:
  https://www.nushell.sh/book/thinking_in_nu.html

=== EXTRA NOTE ===
All blocks are scoped, including variable definition and environment variable changes.

Because of this, the following doesn't work:

def-env cd_with_fallback [arg = ""] {
    let fall_back_path = "/tmp"
    if $arg != "" {
        cd $arg
    } else {
        cd $fall_back_path
    }
}

Instead, you have to use cd in the top level scope:

def-env cd_with_fallback [arg = ""] {
    let fall_back_path = "/tmp"
    let path = if $arg != "" {
        $arg
    } else {
        $fall_back_path
    }
    cd $path
}

Examples

Set environment variable by call a custom command

> def-env foo [] { let-env BAR = "BAZ" }; foo; $env.BAR