diff(1)               UNIX System V(Essential Utilities)                diff(1)


NAME
      diff - differential file comparator

SYNOPSIS
      diff [ -bitw ] [ -c|-e|-f |-h|-n ] filename1 filename2
      diff [ -bitw ] [ -C number ] filename1 filename2
      diff [ -bitw ] [ -D string ] filename1 filename2
      diff [ -bitw ] [ -c|-e| -f|-h|-n ] [-l] [-r] [-s] [ -S name ] directory1
      directory2

DESCRIPTION
      diff tells what lines must be changed in two files to bring them into
      agreement.  If filename1 (filename2) is -, the standard input is used.
      If filename1 (filename2) is a directory, then a file in that directory
      with the name filename2 (filename1) is used.  The normal output 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 filename1 into filename2.
      The numbers after the letters pertain to filename2.  In fact, by
      exchanging a for d and reading backward one may ascertain equally how to
      convert filename2 into filename1.  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 >.

      -b    Ignores trailing blanks (spaces and tabs) and treats other strings
            of blanks as equivalent.

      -i    Ignores the case of letters; for example, `A' will compare equal to
            `a'.

      -t    Expands TAB characters in output lines.  Normal or -c output adds
            character(s) to the front of each line that may adversely affect
            the indentation of the original source lines and make the output
            lines difficult to interpret.  This option will preserve the
            original source's indentation.

      -w    Ignores all blanks (SPACE and TAB characters) and treats all other
            strings of blanks as equivalent; for example, `if ( a == b )' will
            compare equal to `if(a==b)'.

      The following options are mutually exclusive:

      -c    Produces a listing of differences with three lines of context.
            With this option output format is modified slightly:  output begins
            with identification of the files involved and their creation dates,


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diff(1)               UNIX System V(Essential Utilities)                diff(1)


            then each change is separated by a line with a dozen *'s.  The
            lines removed from filename1 are marked with '-'; those added to
            filename2 are marked '+'.  Lines that are changed from one file to
            the other are marked in both files with '!'.

      -C number
            Produces a listing of differences identical to that produced by -c
            with number lines of context.

      -e    Produces a script of a, c, and d commands for the editor ed, which
            will recreate filename2 from filename1.  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

      Except in rare circumstances, diff finds a smallest sufficient set of
      file differences.

      -f    Produces a similar script, not useful with ed, in the opposite
            order.

      -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.  Options -e and -f are unavailable with -h.

      -n    Produces a script similar to -e, but in the opposite order and with
            a count of changed lines on each insert or delete command.

      -D string
            Creates a merged version of filename1 and filename2 with C
            preprocessor controls included so that a compilation of the result
            without defining string is equivalent to compiling filename1, while
            defining string will yield filename2.

      The following options are used for comparing directories:

      -l    Produce output in long format.  Before the diff, each text file is
            piped through pr(1) to paginate it.  Other differences are
            remembered and summarized after all text file differences are
            reported.

      -r    Applies diff recursively to common subdirectories encountered.

      -s    Reports files that are the identical; these would not otherwise be
            mentioned.

      -S name
            Starts a directory diff in the middle, beginning with the file
            name.


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diff(1)               UNIX System V(Essential Utilities)                diff(1)


FILES
      /tmp/d?????
      /usr/lib/diffh for -h
      /usr/bin/pr

SEE ALSO
      bdiff(1), cmp(1), comm(1), ed(1), pr(1).

DIAGNOSTICS
      Exit status is 0 for no differences, 1 for some differences, 2 for
      trouble.

NOTES
      Editing scripts produced under the -e or -f option are naive about
      creating lines consisting of a single period (.).

      Missing newline at end of file X
      indicates that the last line of file X did not have a new-line.  If the
      lines are different, they will be flagged and output; although the output
      will seem to indicate they are the same.


































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