pager.py

# Copyright (c) 2013, Intel Corporation
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are met:
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#       this list of conditions and the following disclaimer.
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#       and/or other materials provided with the distribution.
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#       may be used to endorse or promote products derived from this software
#       without specific prior written permission.
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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"""pager module: context managers to enable and disable the pager."""

__all__ = ["pager", "nopager"]

import contextlib
import os

@contextlib.contextmanager
def _doenv(var, val):
    orig = os.getenv(var)
    os.environ[var] = val
    yield
    if orig is None:
        del os.environ[var]
    else:
        os.environ[var] = orig

@contextlib.contextmanager
def pager():
    """Context manager to enable the pager."""
    with _doenv('pager', '1'):
        yield

@contextlib.contextmanager
def nopager():
    """Context manager to disable the pager."""
    with _doenv('pager', '0'):
        yield