# Shell Tasks


# ShellTask

class

prefect.tasks.shell.ShellTask

(command=None, env=None, helper_script=None, shell="bash", return_all=False, log_stderr=False, **kwargs)[source]

Task for running arbitrary shell commands.

Args:

  • command (string, optional): shell command to be executed; can also be provided post-initialization by calling this task instance
  • env (dict, optional): dictionary of environment variables to use for the subprocess; can also be provided at runtime
  • helper_script (str, optional): a string representing a shell script, which will be executed prior to the command in the same process. Can be used to change directories, define helper functions, etc. when re-using this Task for different commands in a Flow
  • shell (string, optional): shell to run the command with; defaults to "bash"
  • return_all (bool, optional): boolean specifying whether this task should return all lines of stdout as a list, or just the last line as a string; defaults to False
  • log_stderr (bool, optional): boolean specifying whether this task should log the output from stderr in the case of a non-zero exit code; defaults to False
  • **kwargs: additional keyword arguments to pass to the Task constructor
Example:

    from prefect import Flow
    from prefect.tasks.shell import ShellTask

    task = ShellTask(helper_script="cd ~")
    with Flow("My Flow") as f:
        # both tasks will be executed in home directory
        contents = task(command='ls')
        mv_file = task(command='mv .vimrc /.vimrc')

    out = f.run()

methods:                                                                                                                                                       

prefect.tasks.shell.ShellTask.run

(command=None, env=None)[source]

Run the shell command.

Args:

  • command (string): shell command to be executed; can also be provided at task initialization. Any variables / functions defined in self.helper_script will be available in the same process this command runs in
  • env (dict, optional): dictionary of environment variables to use for the subprocess
Returns:
  • stdout (string): if return_all is False (the default), only the last line of stdout is returned, otherwise all lines are returned, which is useful for passing result of shell command to other downstream tasks. If there is no output, None is returned.
Raises:
  • prefect.engine.signals.FAIL: if command has an exit code other than 0



This documentation was auto-generated from commit 4a4acb5
on October 23, 2020 at 16:22 UTC