1  """ndiff [-q] file1 file2
       2      or
       3  ndiff (-r1 | -r2) < ndiff_output > file1_or_file2
       4  
       5  Print a human-friendly file difference report to stdout.  Both inter-
       6  and intra-line differences are noted.  In the second form, recreate file1
       7  (-r1) or file2 (-r2) on stdout, from an ndiff report on stdin.
       8  
       9  In the first form, if -q ("quiet") is not specified, the first two lines
      10  of output are
      11  
      12  -: file1
      13  +: file2
      14  
      15  Each remaining line begins with a two-letter code:
      16  
      17      "- "    line unique to file1
      18      "+ "    line unique to file2
      19      "  "    line common to both files
      20      "? "    line not present in either input file
      21  
      22  Lines beginning with "? " attempt to guide the eye to intraline
      23  differences, and were not present in either input file.  These lines can be
      24  confusing if the source files contain tab characters.
      25  
      26  The first file can be recovered by retaining only lines that begin with
      27  "  " or "- ", and deleting those 2-character prefixes; use ndiff with -r1.
      28  
      29  The second file can be recovered similarly, but by retaining only "  " and
      30  "+ " lines; use ndiff with -r2; or, on Unix, the second file can be
      31  recovered by piping the output through
      32  
      33      sed -n '/^[+ ] /s/^..//p'
      34  """
      35  
      36  __version__ = 1, 7, 0
      37  
      38  import difflib, sys
      39  
      40  def fail(msg):
      41      out = sys.stderr.write
      42      out(msg + "\n\n")
      43      out(__doc__)
      44      return 0
      45  
      46  # open a file & return the file object; gripe and return 0 if it
      47  # couldn't be opened
      48  def fopen(fname):
      49      try:
      50          return open(fname)
      51      except IOError as detail:
      52          return fail("couldn't open " + fname + ": " + str(detail))
      53  
      54  # open two files & spray the diff to stdout; return false iff a problem
      55  def fcompare(f1name, f2name):
      56      f1 = fopen(f1name)
      57      f2 = fopen(f2name)
      58      if not f1 or not f2:
      59          return 0
      60  
      61      a = f1.readlines(); f1.close()
      62      b = f2.readlines(); f2.close()
      63      for line in difflib.ndiff(a, b):
      64          print(line, end=' ')
      65  
      66      return 1
      67  
      68  # crack args (sys.argv[1:] is normal) & compare;
      69  # return false iff a problem
      70  
      71  def main(args):
      72      import getopt
      73      try:
      74          opts, args = getopt.getopt(args, "qr:")
      75      except getopt.error as detail:
      76          return fail(str(detail))
      77      noisy = 1
      78      qseen = rseen = 0
      79      for opt, val in opts:
      80          if opt == "-q":
      81              qseen = 1
      82              noisy = 0
      83          elif opt == "-r":
      84              rseen = 1
      85              whichfile = val
      86      if qseen and rseen:
      87          return fail("can't specify both -q and -r")
      88      if rseen:
      89          if args:
      90              return fail("no args allowed with -r option")
      91          if whichfile in ("1", "2"):
      92              restore(whichfile)
      93              return 1
      94          return fail("-r value must be 1 or 2")
      95      if len(args) != 2:
      96          return fail("need 2 filename args")
      97      f1name, f2name = args
      98      if noisy:
      99          print('-:', f1name)
     100          print('+:', f2name)
     101      return fcompare(f1name, f2name)
     102  
     103  # read ndiff output from stdin, and print file1 (which=='1') or
     104  # file2 (which=='2') to stdout
     105  
     106  def restore(which):
     107      restored = difflib.restore(sys.stdin.readlines(), which)
     108      sys.stdout.writelines(restored)
     109  
     110  if __name__ == '__main__':
     111      main(sys.argv[1:])