# 10.10 `distutils.dep_util` -- Dependency checking

This module provides functions for performing simple, timestamp-based dependency of files and groups of files; also, functions based entirely on such timestamp dependency analysis.

`newer`( | source, target)

  Return true if source exists and is more recently modified than target, or if source exists and target doesn't. Return false if both exist and target is the same age or newer than source. Raise `DistutilsFileError` if source does not exist.

`newer_pairwise`( | sources, targets)

  Walk two filename lists in parallel, testing if each source is newer than its corresponding target. Return a pair of lists (sources, targets) where source is newer than target, according to the semantics of `newer()`

`newer_group`( | sources, target[, missing=`'error'`])

  Return true if target is out-of-date with respect to any file listed in sources In other words, if target exists and is newer than every file in sources, return false; otherwise return true. missing controls what we do when a source file is missing; the default (`'error'`) is to blow up with an `OSError` from inside `os.stat()`; if it is `'ignore'`, we silently drop any missing source files; if it is `'newer'`, any missing source files make us assume that target is out-of-date (this is handy in ``dry-run'' mode: it'll make you pretend to carry out commands that wouldn't work because inputs are missing, but that doesn't matter because you're not actually going to run the commands).