Source Code for Module osh.command.head

 1  # osh 
 2  # Copyright (C) Jack Orenstein <jao@geophile.com> 
 3  # 
 4  # This program is free software; you can redistribute it and/or modify 
 5  # it under the terms of the GNU General Public License as published by 
 6  # the Free Software Foundation; either version 2 of the License, or 
 7  # (at your option) any later version. 
 8  # 
 9  # This program is distributed in the hope that it will be useful, 
10  # but WITHOUT ANY WARRANTY; without even the implied warranty of 
11  # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the 
12  # GNU General Public License for more details. 
13  # 
14  # You should have received a copy of the GNU General Public License 
15  # along with this program; if not, write to the Free Software 
16  # Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. 
17   
18  """C{head N} 
19   
20  The first N items of the input sequence are passed on as output. All other input 
21  is ignored. N must be an integer. 
22   
23  """ 
24   
25  import osh.core 
26   
27  # CLI 
28 -def _head(): 
29      return _Head() 
30   
31  # API 
32 -def head(n): 
33      """The first N items of the input sequence are passed on as output. All other input 
34      is ignored. N must be an integer. 
35      """ 
36      return _Head().process_args(n) 
37   
38 -class _Head(osh.core.Op): 
39   
40      _n = None 
41      _received = None 
42   
43   
44      # object interface 
45   
46 -    def __init__(self): 
47          osh.core.Op.__init__(self, '', (1, 1)) 
48   
49   
50      # BaseOp interface 
51       
52 -    def doc(self): 
53          return __doc__ 
54   
55 -    def setup(self): 
56          args = self.args() 
57          self._n = args.next_int() 
58          self._received = 0 
59   
60 -    def receive(self, object): 
61          self._received += 1 
62          delta = self._n - self._received 
63          if delta >= 0: 
64              self.send(object) 
65