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"""Wrapper around subprocess to run commands."""
from __future__ import annotations
import platform
import re
import subprocess
from typing import TYPE_CHECKING, List, Union
from uuid import uuid4
if TYPE_CHECKING:
import pexpect
class BashProcess:
"""Wrapper for starting subprocesses.
Uses the python built-in subprocesses.run()
Persistent processes are **not** available
on Windows systems, as pexpect makes use of
Unix pseudoterminals (ptys). MacOS and Linux
are okay.
Example:
.. code-block:: python
from langchain_community.utilities.bash import BashProcess
bash = BashProcess(
strip_newlines = False,
return_err_output = False,
persistent = False
)
bash.run('echo \'hello world\'')
"""
strip_newlines: bool = False
"""Whether or not to run .strip() on the output"""
return_err_output: bool = False
"""Whether or not to return the output of a failed
command, or just the error message and stacktrace"""
persistent: bool = False
"""Whether or not to spawn a persistent session
NOTE: Unavailable for Windows environments"""
def __init__(
self,
strip_newlines: bool = False,
return_err_output: bool = False,
persistent: bool = False,
):
"""
Initializes with default settings
"""
self.strip_newlines = strip_newlines
self.return_err_output = return_err_output
self.prompt = ""
self.process = None
if persistent:
self.prompt = str(uuid4())
self.process = self._initialize_persistent_process(self, self.prompt)
@staticmethod
def _lazy_import_pexpect() -> pexpect:
"""Import pexpect only when needed."""
if platform.system() == "Windows":
raise ValueError(
"Persistent bash processes are not yet supported on Windows."
)
try:
import pexpect
except ImportError:
raise ImportError(
"pexpect required for persistent bash processes."
" To install, run `pip install pexpect`."
)
return pexpect
@staticmethod
def _initialize_persistent_process(self: BashProcess, prompt: str) -> pexpect.spawn:
# Start bash in a clean environment
# Doesn't work on windows
"""
Initializes a persistent bash setting in a
clean environment.
NOTE: Unavailable on Windows
Args:
Prompt(str): the bash command to execute
"""
pexpect = self._lazy_import_pexpect()
process = pexpect.spawn(
"env", ["-i", "bash", "--norc", "--noprofile"], encoding="utf-8"
)
# Set the custom prompt
process.sendline("PS1=" + prompt)
process.expect_exact(prompt, timeout=10)
return process
def run(self, commands: Union[str, List[str]]) -> str:
"""
Run commands in either an existing persistent
subprocess or on in a new subprocess environment.
Args:
commands(List[str]): a list of commands to
execute in the session
"""
if isinstance(commands, str):
commands = [commands]
commands = ";".join(commands)
if self.process is not None:
return self._run_persistent(
commands,
)
else:
return self._run(commands)
def _run(self, command: str) -> str:
"""
Runs a command in a subprocess and returns
the output.
Args:
command: The command to run
"""
try:
output = subprocess.run(
command,
shell=True,
check=True,
stdout=subprocess.PIPE,
stderr=subprocess.STDOUT,
).stdout.decode()
except subprocess.CalledProcessError as error:
if self.return_err_output:
return error.stdout.decode()
return str(error)
if self.strip_newlines:
output = output.strip()
return output
def process_output(self, output: str, command: str) -> str:
"""
Uses regex to remove the command from the output
Args:
output: a process' output string
command: the executed command
"""
pattern = re.escape(command) + r"\s*\n"
output = re.sub(pattern, "", output, count=1)
return output.strip()
def _run_persistent(self, command: str) -> str:
"""
Runs commands in a persistent environment
and returns the output.
Args:
command: the command to execute
"""
pexpect = self._lazy_import_pexpect()
if self.process is None:
raise ValueError("Process not initialized")
self.process.sendline(command)
# Clear the output with an empty string
self.process.expect(self.prompt, timeout=10)
self.process.sendline("")
try:
self.process.expect([self.prompt, pexpect.EOF], timeout=10)
except pexpect.TIMEOUT:
return f"Timeout error while executing command {command}"
if self.process.after == pexpect.EOF:
return f"Exited with error status: {self.process.exitstatus}"
output = self.process.before
output = self.process_output(output, command)
if self.strip_newlines:
return output.strip()
return output
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