68 lines
1.7 KiB
Python
68 lines
1.7 KiB
Python
#
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#
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#
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from __future__ import absolute_import, division, print_function, unicode_literals
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#
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#
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#
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import fcntl as _fcntl
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import os.path as _path
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import os as _os
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from solaar import NAME
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_program = NAME.lower()
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del NAME
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from logging import getLogger, DEBUG as _DEBUG
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_log = getLogger(__name__)
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del getLogger
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def check():
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"""Select a file lock location and try to acquire it.
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Suitable locations are $XDG_RUNTIME_DIR, /run/lock, /var/lock, and $TMPDIR.
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The first one found and writable is used.
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"""
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# ensure no more than a single instance runs at a time
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lock_fd = None
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for p in _os.environ.get('XDG_RUNTIME_DIR'), '/run/lock', '/var/lock', _os.environ.get('TMPDIR', '/tmp'):
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# pick the first temporary writable folder
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if p and _path.isdir(p) and _os.access(p, _os.W_OK):
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lock_path = _path.join(p, _program + '.single-instance.' + str(_os.getuid()))
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try:
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lock_fd = open(lock_path, 'wb')
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if _log.isEnabledFor(_DEBUG):
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_log.debug("single-instance lock file is %s", lock_path)
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break
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except:
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pass
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if lock_fd:
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try:
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_fcntl.flock(lock_fd, _fcntl.LOCK_EX | _fcntl.LOCK_NB)
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if _log.isEnabledFor(_DEBUG):
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_log.debug("acquired single-instance lock %s", lock_fd)
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return lock_fd
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except IOError as e:
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if e.errno == 11:
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_log.warn("lock file is busy, %s already running: %s", _program, e)
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import sys
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sys.exit(_program + ": error: already running")
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else:
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raise
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else:
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import sys
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print (_program + ": warning: no suitable location for the lockfile found; ignoring", file=sys.stderr)
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def close(lock_fd):
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"""Release a file lock."""
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if lock_fd:
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_fcntl.flock(lock_fd, _fcntl.LOCK_UN)
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lock_fd.close()
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if _log.isEnabledFor(_DEBUG):
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_log.debug("released single-instance lock %s", lock_fd)
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