DIFF(1)                                                   DIFF(1)

     NAME
          diff - differential file comparator

     SYNOPSIS
          diff [ -efbwr ] file1 ... file2

     DESCRIPTION
          Diff tells what lines must be changed in two files to bring
          them into agreement.  If one file is a directory, then a
          file in that directory with basename the same as that of the
          other file is used.  If both files are directories, simi-
          larly named files in the two directories are compared by the
          method of diff for text files and cmp(1) otherwise.  If more
          than two file names are given, then each argument is com-
          pared to the last argument as above.  The -r option causes
          diff to process similarly named subdirectories recursively.
          The normal output contains lines of these forms:

               n1 a n3,n4
               n1,n2 d n3
               n1,n2 c n3,n4

          These lines resemble Plan 9 or Unix ed commands to convert
          file1 into file2. The numbers after the letters pertain to
          file2. In fact, by exchanging `a' for `d' and reading back-
          ward one may ascertain equally how to convert file2 into
          file1. As in ed, identical pairs where n1 = n2 or n3 = n4
          are abbreviated as a single number.

          Following each of these lines come all the lines that are
          affected in the first file flagged by `<', then all the
          lines that are affected in the second file flagged by `>'.

          The -b option causes trailing blanks (spaces and tabs) to be
          ignored and other strings of blanks to compare equal.  The
          -w option causes all white-space to be removed from input
          lines before applying the difference algorithm.

          The -e option produces a script of a, c and d commands for
          the Plan 9 or Unix editor ed, which will recreate file2 from
          file1. The -f option produces a similar script, not useful
          with ed, in the opposite order. It may, however, be useful
          as input to a stream-oriented post-processor.

          Except in rare circumstances, diff finds a smallest suffi-
          cient set of file differences.

     FILES
          /tmp/diff[12]

     DIFF(1)                                                   DIFF(1)

     SOURCE
          /appl/cmd/diff.b

     DIAGNOSTICS
          Exit status is the empty string for no differences, `some'
          for some, and `error' for trouble.

     SEE ALSO
          cmp(1)

     BUGS
          Editing scripts produced under the -e or -f option are naive
          about creating lines consisting of a single `.'.
          When running diff on directories, the notion of what is a
          text file is open to debate.
          Nothing directly interprets the ed scripts within the
          Inferno environment.