# 2.11BSD#431 - /usr/man/cat1/diff.0

    DIFF(1)             UNIX Programmer's Manual		  DIFF(1)

    NAME
         diff - differential file and directory comparator

    SYNOPSIS
         diff [ -l ] [ -r ] [ -s ] [ -cefhn ] [ -biwt ] dir1 dir2
         diff [ -cefhn ] [ -biwt ] file1 file2
         diff [ -Dstring ] [ -biw ] file1 file2

    DESCRIPTION
         If both arguments are directories, diff sorts the contents
         of the directories by name, and then runs the regular file
         diff algorithm (described below) on text files which are
         different.  Binary files which differ, common subdirec-
         tories, and files which appear in only one directory are
         listed.  Options when comparing directories are:

         -l   long output format; each text file diff is piped
    	  through pr(1) to paginate it, other differences are
    	  remembered and summarized after all text file differ-
    	  ences are reported.

         -r   causes application of diff recursively to common sub-
    	  directories encountered.

         -s   causes diff to report files which are the same, which
    	  are otherwise not mentioned.

         -Sname
    	  starts a directory diff in the middle beginning with
    	  file name.

         When run on regular files, and when comparing text files
         which differ during directory comparison, diff tells what
         lines must be changed in the files to bring them into agree-
         ment.  Except in rare circumstances, diff finds a smallest
         sufficient set of file differences.  If neither file1 nor
         file2 is a directory, then either may be given as `-', in
         which case the standard input is used.  If file1 is a direc-
         tory, then a file in that directory whose file-name is the
         same as the file-name of file2 is used (and vice versa).

         There are several options for output format; the default
         output format contains lines of these forms:

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

         These lines resemble ed commands to convert file1 into
         file2.  The numbers after the letters pertain to file2.  In
         fact, by exchanging `a' for `d' and reading backward one may
         ascertain equally how to convert file2 into file1.  As in

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    DIFF(1)             UNIX Programmer's Manual		  DIFF(1)

         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 `>'.

         Except for -b, -w, -i or -t which may be given with any of
         the others, the following options are mutually exclusive:

         -e       produces a script of a, c and d commands for the
    	      editor ed, which will recreate file2 from file1.
    	      In connection with -e, the following shell program
    	      may help maintain multiple versions of a file.
    	      Only an ancestral file ($1) and a chain of
    	      version-to-version ed scripts ($2,$3,...) made by
    	      diff need be on hand.  A `latest version' appears
    	      on the standard output.

    		      (shift; cat $*; echo '1,$p') | ed - $1

    	      Extra commands are added to the output when compar-
    	      ing directories with -e, so that the result is a
    	      sh(1) script for converting text files which are
    	      common to the two directories from their state in
    	      dir1 to their state in dir2.

         -f       produces a script similar to that of -e, not useful
    	      with ed, and in the opposite order.

         -n       produces a script similar to that of -e, but in the
    	      opposite order and with a count of changed lines on
    	      each insert or delete command.  This is the form
    	      used by rcsdiff(1).

         -c       produces a diff with lines of context.  The default
    	      is to present 3 lines of context and may be
    	      changed, e.g to 10, by -c10.  With -c the output
    	      format is modified slightly: the output beginning
    	      with identification of the files involved and their
    	      creation dates and then each change is separated by
    	      a line with a dozen *'s.	The lines removed from
    	      file1 are marked with `- '; those added to file2
    	      are marked `+ '.	Lines which are changed from one
    	      file to the other are marked in both files with
    	      with `! '.

    	      Changes which lie within <context> lines of each
    	      other are grouped together on output.  (This is a
    	      change from the previous ``diff -c'' but the
    	      resulting output is usually much easier to inter-
    	      pret.)

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    DIFF(1)             UNIX Programmer's Manual		  DIFF(1)

         -h       does a fast, half-hearted job.  It works only when
    	      changed stretches are short and well separated, but
    	      does work on files of unlimited length.

         -Dstring causes diff to create a merged version of file1 and
    	      file2 on the standard output, with C preprocessor
    	      controls included so that a compilation of the
    	      result without defining string is equivalent to
    	      compiling file1, while defining string will yield
    	      file2.

         -b       causes trailing blanks (spaces and tabs) to be
    	      ignored, and other strings of blanks to compare
    	      equal.

         -w       is similar to -b but causes whitespace (blanks and
    	      tabs) to be totally ignored.  E.g.,
    	      ``if ( a == b )'' will compare equal to
    	      ``if(a==b)''.

         -i       ignores the case of letters.  E.g., ``A'' will com-
    	      pare equal to ``a''.

         -t       will expand tabs in output lines.  Normal or -c
    	      output adds character(s) to the front of each line
    	      which may screw up the indentation of the original
    	      source lines and make the output listing difficult
    	      to interpret.  This option will preserve the origi-
    	      nal source's indentation.

    FILES
         /tmp/d?????
         /usr/libexec/diffh for -h
         /bin/diff for directory diffs
         /bin/pr

    SEE ALSO
         cmp(1), cc(1), comm(1), ed(1), diff3(1)

    DIAGNOSTICS
         Exit status is 0 for no differences, 1 for some, 2 for trou-
         ble.

    BUGS
         Editing scripts produced under the -e or -f option are naive
         about creating lines consisting of a single `.'.

         When comparing directories with the -b, -w or -i options
         specified, diff first compares the files ala cmp, and then
         decides to run the diff algorithm if they are not equal.
         This may cause a small amount of spurious output if the
         files then turn out to be identical because the only

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    DIFF(1)             UNIX Programmer's Manual		  DIFF(1)

         differences are insignificant blank string or case differ-
         ences.

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