1 """distutils.dep_util 2 3 Utility functions for simple, timestamp-based dependency of files 4 and groups of files; also, function based entirely on such 5 timestamp dependency analysis.""" 6 7 __revision__ = "$Id$" 8 9 import os 10 from distutils.errors import DistutilsFileError 11 12 def newer(source, target): 13 """Tells if the target is newer than the source. 14 15 Return true if 'source' exists and is more recently modified than 16 'target', or if 'source' exists and 'target' doesn't. 17 18 Return false if both exist and 'target' is the same age or younger 19 than 'source'. Raise DistutilsFileError if 'source' does not exist. 20 21 Note that this test is not very accurate: files created in the same second 22 will have the same "age". 23 """ 24 if not os.path.exists(source): 25 raise DistutilsFileError("file '%s' does not exist" % 26 os.path.abspath(source)) 27 if not os.path.exists(target): 28 return True 29 30 return os.stat(source).st_mtime > os.stat(target).st_mtime 31 32 def newer_pairwise(sources, targets): 33 """Walk two filename lists in parallel, testing if each source is newer 34 than its corresponding target. Return a pair of lists (sources, 35 targets) where source is newer than target, according to the semantics 36 of 'newer()'. 37 """ 38 if len(sources) != len(targets): 39 raise ValueError, "'sources' and 'targets' must be same length" 40 41 # build a pair of lists (sources, targets) where source is newer 42 n_sources = [] 43 n_targets = [] 44 for source, target in zip(sources, targets): 45 if newer(source, target): 46 n_sources.append(source) 47 n_targets.append(target) 48 49 return n_sources, n_targets 50 51 def newer_group(sources, target, missing='error'): 52 """Return true if 'target' is out-of-date with respect to any file 53 listed in 'sources'. 54 55 In other words, if 'target' exists and is newer 56 than every file in 'sources', return false; otherwise return true. 57 'missing' controls what we do when a source file is missing; the 58 default ("error") is to blow up with an OSError from inside 'stat()'; 59 if it is "ignore", we silently drop any missing source files; if it is 60 "newer", any missing source files make us assume that 'target' is 61 out-of-date (this is handy in "dry-run" mode: it'll make you pretend to 62 carry out commands that wouldn't work because inputs are missing, but 63 that doesn't matter because you're not actually going to run the 64 commands). 65 """ 66 # If the target doesn't even exist, then it's definitely out-of-date. 67 if not os.path.exists(target): 68 return True 69 70 # Otherwise we have to find out the hard way: if *any* source file 71 # is more recent than 'target', then 'target' is out-of-date and 72 # we can immediately return true. If we fall through to the end 73 # of the loop, then 'target' is up-to-date and we return false. 74 target_mtime = os.stat(target).st_mtime 75 76 for source in sources: 77 if not os.path.exists(source): 78 if missing == 'error': # blow up when we stat() the file 79 pass 80 elif missing == 'ignore': # missing source dropped from 81 continue # target's dependency list 82 elif missing == 'newer': # missing source means target is 83 return True # out-of-date 84 85 if os.stat(source).st_mtime > target_mtime: 86 return True 87 88 return False 89
