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Pipe Buffer Size #203

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Merged
merged 3 commits into from
Aug 10, 2017
Merged

Pipe Buffer Size #203

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a2df310
Added pipe buffer size that can be tweaked if stdin/stdout need to be…
kmvanbrunt Aug 10, 2017
2db18d0
Merge branch 'master' into buffer_size
tleonhardt Aug 10, 2017
c5f9ca9
Improved comment
kmvanbrunt Aug 10, 2017
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21 changes: 16 additions & 5 deletions cmd2.py
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Original file line number Diff line number Diff line change
Expand Up @@ -82,6 +82,12 @@
except ImportError:
pass

# BrokenPipeError is only in Python 3. Use IOError for Python 2.
if six.PY3:
BROKEN_PIPE_ERROR = BrokenPipeError
else:
BROKEN_PIPE_ERROR = IOError

__version__ = '0.7.6'

# Pyparsing enablePackrat() can greatly speed up parsing, but problems have been seen in Python 3 in the past
Expand Down Expand Up @@ -539,6 +545,11 @@ def __init__(self, completekey='tab', stdin=None, stdout=None, use_ipython=False
# Used when piping command output to a shell command
self.pipe_proc = None

# Size of the stdin/stdout buffers used when piping command output to a shell command via self.stdout.
# This should be increased in cases where large amounts of data are expected to be piped to the shell
# to prevent blocking when writing to self.stdout.
self._pipe_buffer_size = io.DEFAULT_BUFFER_SIZE

# ----- Methods related to presenting output to the user -----

@property
Expand Down Expand Up @@ -575,7 +586,7 @@ def poutput(self, msg, end='\n'):
self.stdout.write(msg_str)
if not msg_str.endswith(end):
self.stdout.write(end)
except BrokenPipeError:
except BROKEN_PIPE_ERROR:
# This occurs if a command's output is being piped to another process and that process closes before the
# command is finished. We intentionally don't print a warning message here since we know that stdout
# will be restored by the _restore_output() method. If you would like your application to print a
Expand Down Expand Up @@ -805,9 +816,9 @@ def _redirect_output(self, statement):

# Open each side of the pipe and set stdout accordingly
# noinspection PyTypeChecker
self.stdout = io.open(write_fd, write_mode)
self.stdout = io.open(write_fd, write_mode, buffering=self._pipe_buffer_size)
# noinspection PyTypeChecker
subproc_stdin = io.open(read_fd, read_mode)
subproc_stdin = io.open(read_fd, read_mode, buffering=self._pipe_buffer_size)

# We want Popen to raise an exception if it fails to open the process. Thus we don't set shell to True.
try:
Expand Down Expand Up @@ -852,7 +863,7 @@ def _restore_output(self, statement):
try:
# Close the file or pipe that stdout was redirected to
self.stdout.close()
except BrokenPipeError:
except BROKEN_PIPE_ERROR:
pass
finally:
# Restore self.stdout
Expand Down Expand Up @@ -2352,7 +2363,7 @@ def __nonzero__(self):
if __name__ == '__main__':
# If run as the main application, simply start a bare-bones cmd2 application with only built-in functionality.

# Set "use_iptyhon" to True to include the ipy command if IPython is installed, which supports advanced interactive
# Set "use_ipython" to True to include the ipy command if IPython is installed, which supports advanced interactive
# debugging of your application via introspection on self.
app = Cmd(use_ipython=False)
app.cmdloop()