find: Comparing Timestamps

 
 2.4.2 Comparing Timestamps
 --------------------------
 
  -- Test: -newerXY reference
      Succeeds if timestamp 'X' of the file being considered is newer
      than timestamp 'Y' of the file 'reference'.  The letters 'X' and
      'Y' can be any of the following letters:
 
      'a'
           Last-access time of 'reference'
      'B'
           Birth time of 'reference' (when this is not known, the test
           cannot succeed)
      'c'
           Last-change time of 'reference'
      'm'
           Last-modification time of 'reference'
      't'
           The 'reference' argument is interpreted as a literal time,
           rather than the name of a file.  ⇒Date input formats,
           for a description of how the timestamp is understood.  Tests
           of the form '-newerXt' are valid but tests of the form
           '-newertY' are not.
 
      For example the test '-newerac /tmp/foo' succeeds for all files
      which have been accessed more recently than '/tmp/foo' was changed.
      Here 'X' is 'a' and 'Y' is 'c'.
 
      Not all files have a known birth time.  If 'Y' is 'b' and the birth
      time of 'reference' is not available, 'find' exits with an
      explanatory error message.  If 'X' is 'b' and we do not know the
      birth time the file currently being considered, the test simply
      fails (that is, it behaves like '-false' does).
 
      Some operating systems (for example, most implementations of Unix)
      do not support file birth times.  Some others, for example
      NetBSD-3.1, do.  Even on operating systems which support file birth
      times, the information may not be available for specific files.
      For example, under NetBSD, file birth times are supported on UFS2
      file systems, but not UFS1 file systems.
 
    There are two ways to list files in '/usr' modified after February 1
 of the current year.  One uses '-newermt':
 
      find /usr -newermt "Feb 1"
 
    The other way of doing this works on the versions of find before
 4.3.3:
 
      touch -t 02010000 /tmp/stamp$$
      find /usr -newer /tmp/stamp$$
      rm -f /tmp/stamp$$
 
  -- Test: -anewer reference
  -- Test: -cnewer reference
  -- Test: -newer reference
      True if the time of the last access (or status change or data
      modification) of the current file is more recent than that of the
      last data modification of the REFERENCE file.  As such, '-anewer'
      is equivalent to '-neweram', '-cnewer' to '-newercm', and '-newer'
      to '-newermm'.
 
      If REFERENCE is a symbolic link and the '-H' option or the '-L'
      option is in effect, then the time of the last data modification of
      the file it points to is always used.
 
      These tests are affected by '-follow' only if '-follow' comes
      before them on the command line.  ⇒Symbolic Links, for more
      information on '-follow'.
 
      As an example, to list any files modified since '/bin/sh' was last
      modified:
 
           find . -newer /bin/sh
 
  -- Test: -used n
      True if the file was last accessed N days after its status was last
      changed.  Useful for finding files that are not being used, and
      could perhaps be archived or removed to save disk space.