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 stat import ST_MTIME 11 from distutils.errors import DistutilsFileError 12 13 def newer(source, target): 14 """Tells if the target is newer than the source. 15 16 Return true if 'source' exists and is more recently modified than 17 'target', or if 'source' exists and 'target' doesn't. 18 19 Return false if both exist and 'target' is the same age or younger 20 than 'source'. Raise DistutilsFileError if 'source' does not exist. 21 22 Note that this test is not very accurate: files created in the same second 23 will have the same "age". 24 """ 25 if not os.path.exists(source): 26 raise DistutilsFileError("file '%s' does not exist" % 27 os.path.abspath(source)) 28 if not os.path.exists(target): 29 return True 30 31 return os.stat(source)[ST_MTIME] > os.stat(target)[ST_MTIME] 32 33 def newer_pairwise(sources, targets): 34 """Walk two filename lists in parallel, testing if each source is newer 35 than its corresponding target. Return a pair of lists (sources, 36 targets) where source is newer than target, according to the semantics 37 of 'newer()'. 38 """ 39 if len(sources) != len(targets): 40 raise ValueError, "'sources' and 'targets' must be same length" 41 42 # build a pair of lists (sources, targets) where source is newer 43 n_sources = [] 44 n_targets = [] 45 for source, target in zip(sources, targets): 46 if newer(source, target): 47 n_sources.append(source) 48 n_targets.append(target) 49 50 return n_sources, n_targets 51 52 def newer_group(sources, target, missing='error'): 53 """Return true if 'target' is out-of-date with respect to any file 54 listed in 'sources'. 55 56 In other words, if 'target' exists and is newer 57 than every file in 'sources', return false; otherwise return true. 58 'missing' controls what we do when a source file is missing; the 59 default ("error") is to blow up with an OSError from inside 'stat()'; 60 if it is "ignore", we silently drop any missing source files; if it is 61 "newer", any missing source files make us assume that 'target' is 62 out-of-date (this is handy in "dry-run" mode: it'll make you pretend to 63 carry out commands that wouldn't work because inputs are missing, but 64 that doesn't matter because you're not actually going to run the 65 commands). 66 """ 67 # If the target doesn't even exist, then it's definitely out-of-date. 68 if not os.path.exists(target): 69 return True 70 71 # Otherwise we have to find out the hard way: if *any* source file 72 # is more recent than 'target', then 'target' is out-of-date and 73 # we can immediately return true. If we fall through to the end 74 # of the loop, then 'target' is up-to-date and we return false. 75 target_mtime = os.stat(target)[ST_MTIME] 76 77 for source in sources: 78 if not os.path.exists(source): 79 if missing == 'error': # blow up when we stat() the file 80 pass 81 elif missing == 'ignore': # missing source dropped from 82 continue # target's dependency list 83 elif missing == 'newer': # missing source means target is 84 return True # out-of-date 85 86 if os.stat(source)[ST_MTIME] > target_mtime: 87 return True 88 89 return False 90
