shell-skill

Shell Tool

Execute short-lived shell commands in the workflow workspace. The backend uses Nushell when nu is installed. Otherwise it passes the command to the host shell (cmd.exe on Windows or the platform /bin/sh-style shell on POSIX). Shell-specific syntax is therefore conditional on the installed runner.

External binaries on PATH (npm, node, python, git, etc.) are available to whichever runner is selected.

For portable calls, prefer one external command with ordinary arguments, such as git status or python -V. Use file_read, file_modify, or fs_search for filesystem work; they avoid runner-specific parsing.

Runner-dependent syntax

The node rejects space-delimited && and || before selecting a runner, so those operators are unsupported even when the host shell would normally accept them. Prefer separate tool calls. If the environment is known to have Nushell, its equivalents include:

try { npm install } catch { print 'install failed'; exit 1 }
open README.md --raw | lines | first 20

Do not send Nushell pipelines, Bash substitutions, PowerShell cmdlets, or cmd.exe builtins unless the selected environment is known to support that syntax. GNU utilities such as sed, awk, and grep are not generally available on Windows.

shell_execute Tool

Schema

Field	Type	Required	Description
command	string	Yes	Command interpreted by Nushell when installed, otherwise by the host shell
timeout	int	No	Seconds (default 30, max 600)

Response

{
  "stdout": "command output",
  "exit_code": 0,
  "truncated": false,
  "command": "ls"
}

Exit code	Meaning
0	Success
124	Timed out
non-zero	Failure

Nushell reference (only when nu is installed)

Bash / cmd.exe form	Nushell form
cmd1 && cmd2 (and-then)	cmd1; cmd2 (unconditional sequential — see below for short-circuit)
`cmd1
$VAR substitution	$env.VAR
`cmd` or $(cmd)	(cmd) (parens, no dollar)
cmd > file.txt	cmd | save file.txt
cmd >> file.txt	cmd | save --append file.txt
cmd 2>&1	cmd | complete | get stdout (all output is captured anyway)
if [ -f x.txt ]; then ...	if ('x.txt' | path exists) { ... }
for f in *.py; do ...	glob '*.py' | each { |f| ... }
* glob in argv (auto-expand)	wrap in quotes or use glob
~/path	('~/path' | path expand)
sed -n '1,N p' file	open file --raw | lines | first N (prefer file_read with limit)
head -n N file	open file --raw | lines | first N
tail -n N file	open file --raw | lines | last N
sed -i 's/a/b/' file	use file_modify (edit op) — not the shell
grep 'pat' file	open file --raw | find 'pat' (prefer fs_search)
grep -r 'pat' src/	use fs_search (grep mode)
wc -l file	open file --raw | lines | length
find . -name '*.py'	glob '**/*.py'
xargs cmd	each { |x| cmd $x }