Source code for ubelt.util_cmd

# -*- coding: utf-8 -*-
This module exposes the :func:`ubelt.cmd` command, which provides a simple
means for interacting with the commandline. While this does use
:class:`subprocess.Popen` under the hood, the key draw of :func:`ubelt.cmd` is
that you can capture stdout/stderr in your program while simultaneously
printing it to the terminal in real time.

    >>> import ubelt as ub
    >>> # Running with verbose=1 will write to stdout in real time
    >>> info = ub.cmd('echo "write your command naturally"', verbose=1)
    write your command naturally
    >>> # Unless `detatch=True`, `cmd` always returns an info dict.
    >>> print('info = ' + ub.repr2(info))
    info = {
        'command': 'echo "write your command naturally"',
        'cwd': None,
        'err': '',
        'out': 'write your command naturally\n',
        'proc': <...Popen...>,
        'ret': 0,
from __future__ import absolute_import, division, print_function, unicode_literals
import sys
import warnings

__all__ = ['cmd']

POSIX = 'posix' in sys.builtin_module_names

    import select
else:  # nocover
    select = NotImplemented

PY2 = sys.version_info[0] == 2
PY34 = sys.version_info[0:2] == (3, 4)
if PY2:
    import six
    string_types = six.string_types
    string_types = (str,)

def _textio_iterlines(stream):
    Iterates over lines in a TextIO stream until an EOF is encountered.
    This is the iterator version of stream.readlines()
    line = stream.readline()
    while line != '':
        yield line
        line = stream.readline()

def _proc_async_iter_stream(proc, stream, buffersize=1):
    Reads output from a process in a separate thread
    from six.moves import queue
    from threading import Thread
    def enqueue_output(proc, stream, stream_queue):
        while proc.poll() is None:
            line = stream.readline()
            # print('ENQUEUE LIVE {!r} {!r}'.format(stream, line))

        for line in _textio_iterlines(stream):
            # print('ENQUEUE FINAL {!r} {!r}'.format(stream, line))

        # print("STREAM IS DONE {!r}".format(stream))
        stream_queue.put(None)  # signal that the stream is finished
        # stream.close()
    stream_queue = queue.Queue(maxsize=buffersize)
    _thread = Thread(target=enqueue_output, args=(proc, stream, stream_queue))
    _thread.daemon = True  # thread dies with the program
    return stream_queue

def _proc_iteroutput_thread(proc):
    Iterates over output from a process line by line

        WARNING. Current implementation might have bugs with other threads.
        This behavior was seen when using earlier versions of tqdm. I'm not
        sure if this was our bug or tqdm's. Newer versions of tqdm fix this,
        but I cannot guarantee that there isn't an issue on our end.

        Tuple[str, str]: oline, eline: stdout and stderr line

        .. [SO_375427]
    from six.moves import queue

    # Create threads that read stdout / stderr and queue up the output
    stdout_queue = _proc_async_iter_stream(proc, proc.stdout)
    stderr_queue = _proc_async_iter_stream(proc, proc.stderr)

    stdout_live = True
    stderr_live = True

    # read from the output asynchronously until
    while stdout_live or stderr_live:
        if stdout_live:  # pragma: nobranch
                oline = stdout_queue.get_nowait()
                stdout_live = oline is not None
            except queue.Empty:
                oline = None
        if stderr_live:
                eline = stderr_queue.get_nowait()
                stderr_live = eline is not None
            except queue.Empty:
                eline = None
        if oline is not None or eline is not None:
            yield oline, eline

def _proc_iteroutput_select(proc):
    Iterates over output from a process line by line

    UNIX only. Use :func:`_proc_iteroutput_thread` instead for a cross platform
    solution based on threads.

        Tuple[str, str]: oline, eline: stdout and stderr line
    from six.moves import zip_longest
    # Read output while the external program is running
    while proc.poll() is None:
        reads = [proc.stdout.fileno(), proc.stderr.fileno()]
        ret =, [], [])
        oline = eline = None
        for fd in ret[0]:
            if fd == proc.stdout.fileno():
                oline = proc.stdout.readline()
            if fd == proc.stderr.fileno():
                eline = proc.stderr.readline()
        yield oline, eline

    # Grab any remaining data in stdout and stderr after the process finishes
    oline_iter = _textio_iterlines(proc.stdout)
    eline_iter = _textio_iterlines(proc.stderr)
    for oline, eline in zip_longest(oline_iter, eline_iter):
        yield oline, eline

def _tee_output(proc, stdout=None, stderr=None, backend='thread'):
    Simultaneously reports and captures stdout and stderr from a process

    subprocess must be created using (stdout=subprocess.PIPE,
    logged_out = []
    logged_err = []
    if backend == 'auto':
        # backend = 'select' if POSIX else 'thread'
        backend = 'thread'

    if backend == 'select':
        if not POSIX:  # nocover
            raise NotImplementedError('select is only available on posix')
        # the select-based version is stable, but slow
        _proc_iteroutput = _proc_iteroutput_select
    elif backend == 'thread':
        # the thread version is fast, but might run into issues.
        _proc_iteroutput = _proc_iteroutput_thread
    else:  # nocover
        # The value of "backend" should be checked before we create the
        # processes, otherwise we will have a dangling process
        raise AssertionError('Validate "backend" before creating the proc')

    for oline, eline in _proc_iteroutput(proc):
        if oline:
            if stdout:  # pragma: nobranch
        if eline:
            if stderr:  # pragma: nobranch
    return proc, logged_out, logged_err

[docs]def cmd(command, shell=False, detach=False, verbose=0, tee=None, cwd=None, env=None, tee_backend='auto', check=False, **kwargs): """ Executes a command in a subprocess. The advantage of this wrapper around subprocess is that (1) you control if the subprocess prints to stdout, (2) the text written to stdout and stderr is returned for parsing, (3) cross platform behavior that lets you specify the command as a string or tuple regardless of whether or not shell=True. (4) ability to detach, return the process object and allow the process to run in the background (eventually we may return a Future object instead). Args: command (str | List[str]): bash-like command string or tuple of executable and args shell (bool, default=False): if True, process is run in shell. detach (bool, default=False): if True, process is detached and run in background. verbose (int, default=0): verbosity mode. Can be 0, 1, 2, or 3. tee (bool | None): if True, simultaneously writes to stdout while capturing output from the command. If not specified, defaults to True if verbose > 0. If detach is True, then this argument is ignored. cwd (str | PathLike | None): Path to run command. Defaults to current working directory if unspecified. env (Dict[str, str] | None): environment passed to Popen tee_backend (str, default='auto'): backend for tee output. Valid choices are: "auto", "select" (POSIX only), and "thread". check (bool, default=False): if True, check that the return code was zero before returning, otherwise raise a CalledProcessError. Does nothing if detach is True. **kwargs: only used to support deprecated arguments Returns: dict: info - information about command status. if detach is False ``info`` contains captured standard out, standard error, and the return code if detach is False ``info`` contains a reference to the process. Note: Inputs can either be text or tuple based. On UNIX we ensure conversion to text if shell=True, and to tuple if shell=False. On windows, the input is always text based. See [SO_33560364]_ for a potential cross-platform shlex solution for windows. CommandLine: xdoctest -m ubelt.util_cmd cmd:6 python -c "import ubelt as ub; ub.cmd('ping localhost -c 2', verbose=2)" pytest "$(python -c 'import ubelt; print(ubelt.util_cmd.__file__)')" -sv --xdoctest-verbose 2 References: .. [SO_11495783] .. [SO_7729336] .. [SO_33560364] Example: >>> import ubelt as ub >>> info = ub.cmd(('echo', 'simple cmdline interface'), verbose=1) simple cmdline interface >>> assert info['ret'] == 0 >>> assert info['out'].strip() == 'simple cmdline interface' >>> assert info['err'].strip() == '' Example: >>> import ubelt as ub >>> info = ub.cmd('echo str noshell', verbose=0) >>> assert info['out'].strip() == 'str noshell' Example: >>> # windows echo will output extra single quotes >>> import ubelt as ub >>> info = ub.cmd(('echo', 'tuple noshell'), verbose=0) >>> assert info['out'].strip().strip("'") == 'tuple noshell' Example: >>> # Note this command is formatted to work on win32 and unix >>> import ubelt as ub >>> info = ub.cmd('echo str&&echo shell', verbose=0, shell=True) >>> assert info['out'].strip() == 'str' + chr(10) + 'shell' Example: >>> import ubelt as ub >>> info = ub.cmd(('echo', 'tuple shell'), verbose=0, shell=True) >>> assert info['out'].strip().strip("'") == 'tuple shell' Example: >>> import pytest >>> import ubelt as ub >>> info = ub.cmd('echo hi', check=True) >>> import subprocess >>> with pytest.raises(subprocess.CalledProcessError): >>> ub.cmd('exit 1', check=True, shell=True) Example: >>> import ubelt as ub >>> from os.path import join, exists >>> fpath1 = join(ub.get_app_cache_dir('ubelt'), 'cmdout1.txt') >>> fpath2 = join(ub.get_app_cache_dir('ubelt'), 'cmdout2.txt') >>> ub.delete(fpath1) >>> ub.delete(fpath2) >>> # Start up two processes that run simultaneously in the background >>> info1 = ub.cmd(('touch', fpath1), detach=True) >>> info2 = ub.cmd('echo writing2 > ' + fpath2, shell=True, detach=True) >>> # Detached processes are running in the background >>> # We can run other code while we wait for them. >>> while not exists(fpath1): ... pass >>> while not exists(fpath2): ... pass >>> # communicate with the process before you finish >>> # (otherwise you may leak a text wrapper) >>> info1['proc'].communicate() >>> info2['proc'].communicate() >>> # Check that the process actually did finish >>> assert (info1['proc'].wait()) == 0 >>> assert (info2['proc'].wait()) == 0 >>> # Check that the process did what we expect >>> assert ub.readfrom(fpath1) == '' >>> assert ub.readfrom(fpath2).strip() == 'writing2' """ import subprocess # TODO: stdout, stderr - experimental - custom file to pipe stdout/stderr to if kwargs: # nocover if 'verbout' in kwargs: warnings.warn( '`verbout` is deprecated and will be removed. ' 'Use `tee` instead', DeprecationWarning) tee = kwargs.pop('verbout') if 'detatch' in kwargs: warnings.warn( '`detatch` is deprecated (misspelled) and will be removed. ' 'Use `detach` instead', DeprecationWarning) detach = kwargs.pop('detatch') if kwargs: raise ValueError('Unknown kwargs: {}'.format(list(kwargs.keys()))) # Determine if command is specified as text or a tuple if isinstance(command, string_types): command_text = command command_tup = None else: import pipes command_tup = command command_text = ' '.join(list(map(pipes.quote, command_tup))) if shell or sys.platform.startswith('win32'): # When shell=True, args is sent to the shell (e.g. bin/sh) as text args = command_text else: # When shell=False, args is a list of executable and arguments if command_tup is None: # parse this out of the string # NOTE: perhaps use the solution from [3] here? import shlex command_tup = shlex.split(command_text) # command_tup = shlex.split(command_text, posix=not WIN32) args = command_tup if tee is None: tee = verbose > 0 if tee and tee_backend not in {'auto', 'thread', 'select'}: raise ValueError('tee_backend must be select, thread, or auto') if verbose > 1: import os import platform import getpass from ubelt import shrinkuser if verbose > 2: try: print('┌─── START CMD ───') except Exception: # nocover print('+=== START CMD ===') cwd_ = os.getcwd() if cwd is None else cwd compname = platform.node() username = getpass.getuser() cwd_ = shrinkuser(cwd_) ps1 = '[ubelt.cmd] {}@{}:{}$ '.format(username, compname, cwd_) print(ps1 + command_text) # Create a new process to execute the command def make_proc(): # delay the creation of the process until we validate all args proc = subprocess.Popen(args, stdout=subprocess.PIPE, stderr=subprocess.PIPE, shell=shell, universal_newlines=True, cwd=cwd, env=env) return proc if detach: info = {'proc': make_proc(), 'command': command_text} if verbose > 0: # nocover print('...detaching') else: if tee: # We logging stdout and stderr, while simulaniously piping it to # another stream. stdout = sys.stdout stderr = sys.stderr proc = make_proc() proc, logged_out, logged_err = _tee_output(proc, stdout, stderr, backend=tee_backend) try: out = ''.join(logged_out) except UnicodeDecodeError: # nocover out = '\n'.join(_.decode('utf-8') for _ in logged_out) try: err = ''.join(logged_err) except UnicodeDecodeError: # nocover err = '\n'.join(_.decode('utf-8') for _ in logged_err) (out_, err_) = proc.communicate() else: proc = make_proc() (out, err) = proc.communicate() # calling wait means that the process will terminate and it is safe to # return a reference to the process object. ret = proc.wait() info = { 'out': out, 'err': err, 'ret': ret, 'proc': proc, 'cwd': cwd, 'command': command_text } if verbose > 2: # try: print('└─── END CMD ───') except Exception: # nocover print('L___ END CMD ___') if check: if info['ret'] != 0: if PY2 or PY34: raise subprocess.CalledProcessError( info['ret'], info['command'], info['out']) else: raise subprocess.CalledProcessError( info['ret'], info['command'], info['out'], info['err']) return info