"""Shell detection utilities for completion generation.
This module provides functionality to detect the current shell type by inspecting
environment variables. This is useful for dynamically generating appropriate completion
scripts for different shell environments.
"""
import os
import subprocess
from pathlib import Path
from typing import Literal
class ShellDetectionError(Exception):
"""Raised when the shell type cannot be detected."""
def _extract_shell_name(shell_string: str) -> Literal["zsh", "bash", "fish"] | None:
"""Extract shell name from a string (path or process name).
Parameters
----------
shell_string : str
String that may contain a shell name (e.g., "/bin/bash", "zsh", "-bash").
Returns
-------
Literal["zsh", "bash", "fish"] | None
The detected shell type, or None if not recognized.
"""
shell_lower = shell_string.lower()
if "zsh" in shell_lower:
return "zsh"
elif "bash" in shell_lower:
return "bash"
elif "fish" in shell_lower:
return "fish"
return None
def detect_shell() -> Literal["zsh", "bash", "fish"]:
"""Detect the current shell type using multiple detection methods.
Returns
-------
Literal["zsh", "bash", "fish"]
The detected shell type.
Raises
------
ShellDetectionError
If the shell type cannot be determined from any detection method.
Examples
--------
>>> shell = detect_shell() # doctest: +SKIP
>>> print(f"Detected shell: {shell}") # doctest: +SKIP
Detected shell: bash
"""
if os.environ.get("ZSH_VERSION"):
return "zsh"
elif os.environ.get("BASH_VERSION"):
return "bash"
elif os.environ.get("FISH_VERSION"):
return "fish"
try:
ppid = os.getppid()
result = subprocess.run(
["ps", "-p", str(ppid), "-o", "comm="],
capture_output=True,
text=True,
timeout=1,
)
if result.returncode == 0 and result.stdout:
parent_process = result.stdout.strip()
shell = _extract_shell_name(parent_process)
if shell:
return shell
except (subprocess.SubprocessError, FileNotFoundError, OSError):
pass
shell_path = os.environ.get("SHELL", "")
if shell_path:
shell_name = Path(shell_path).name
shell = _extract_shell_name(shell_name)
if shell:
return shell
raise ShellDetectionError("Unable to detect shell type.")
