nushell

Original：🇺🇸 English

Translated

Use when writing or running Nushell commands, scripts, or pipelines - via the Nushell MCP server (mcp__nushell__evaluate), via Bash (nu -c), or in .nu script files. Also use when working with structured data (JSON, YAML, TOML, CSV, Parquet, SQLite), doing ad-hoc data analysis or exploration, or when the user's shell is Nushell.

1installs

Sourcenushell/nu_scripts

Added on2026-03-14

NPX Install

npx skill4agent add nushell/nu_scripts nushell

SKILL.md Content

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Using Nushell

Nushell is a structured-data shell. Commands pass tables, records, and lists through pipelines - not text.

Two execution paths:

MCP server:
```
mcp__nushell__evaluate
```
- persistent REPL (variables survive across calls)
Bash tool:
```
nu -c '<code>'
```
- one-shot (use single quotes for outer wrapper)

Critical Rules

NEVER use bare
print
in MCP stdio mode. Output will be lost (returns empty

[]

). Use

print -e "msg"

for stderr, or just return the value (implicit return).

String interpolation uses parentheses, NOT curly braces:

nu

# WRONG:  $"hello {$name}"
# CORRECT: $"hello ($name)"
$"($env.HOME)/docs"    $"2 + 2 = (2 + 2)"    $"files: (ls | length)"

Gotcha:

$"(some text)"

errors - parens are evaluated as code. Escape literal parens:

\(text\)

.

No bash syntax:

cmd1; cmd2

not

&&

,

o+e>|

not

2>&1

,

$env.VAR

not

$VAR

,

(cmd)

not

$(cmd)

.

Common Mistakes

Mistake	Fix
`$"hello {$name}"`	`$"hello ($name)"`
`print "msg"` in MCP	`print -e "msg"` or return value
`command 2>&1`	`command o+e>\| ...`
`$HOME/path`	`$env.HOME` or `$"($env.HOME)/path"`
`export FOO=bar`	`$env.FOO = "bar"`
Mutating in closure	Use `reduce` , `generate` , or `each`
`\u001b` for ANSI	`ansi strip` to remove, `char --unicode '1b'` for ESC
`where ($in.a > 1) and ($in.b > 2)`	Second `$in` rebinds to bool. Use bare cols: `where a > 1 and b > 2`
`where not ($in.col \| cmd)`	`not` breaks `$in` . Use `where ($in.col \| cmd) == false`
`where col \| cmd` (no parens)	Parsed as two pipeline stages. Use `where ($in.col \| cmd)`

When to Use Nushell

Always prefer Nushell for:

Any structured data (JSON, YAML, TOML, CSV, Parquet, SQLite) - unifies all formats
CLI tools with
```
--json
```
flags - pipe JSON output directly into Nushell for querying (e.g.
```
^gh pr list --json title,state | from json
```
)
Ad-hoc data analysis and exploration - faster than Python setup
Initial data science/analytics - histograms, tabular output, basic aggregations
Polars plugin for large datasets - DataFrames without Python overhead

Use Bash only when: bash-specific tooling, MCP unavailable, or bash-syntax integrations.

Reference Files

Read the relevant file(s) based on what you need:

File	Read when you need...
commands.md	Command reference tables (filters, strings, conversions, filesystem, math, dates)
types-and-syntax.md	Type system, string types, operators, variables, control flow, cell-paths
data-analysis.md	Format conversion, HTTP, Polars, SQLite, aggregation patterns
advanced.md	Custom commands, modules, error handling, jobs, external commands, env config
bash-equivalents.md	Complete Bash-to-Nushell translation table
http-transport.md	Differences when using HTTP transport instead of stdio

MCP Server Quick Notes

mcp__nushell__evaluate

- run code;

mcp__nushell__list_commands

- discover;

mcp__nushell__command_help

- help

State persists between calls.
```
$history
```
stores prior results (access
```
$history.0
```
, etc.)
Use
```
| to text
```
or
```
| to json
```
for large outputs. Use
```
ansi strip
```
for color removal.