DIFF(1-SysV)        RISC/os Reference Manual         DIFF(1-SysV)



NAME
     diff - differential file comparator

SYNOPSIS
     diff [ -efbh ] file1 file2

DESCRIPTION
     diff tells what lines must be changed in two files to bring
     them into agreement.  If file1 (file2) is -, the standard
     input is used.  If file1 (file2) is a directory, then a file
     in that directory with the name file2 (file1) 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 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
     ed, identical pairs, where n1 = n2 or n3 = n4, are abbrevi-
     ated 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 -e option produces a script of a, c, and d commands for
     the editor ed, which will recreate file2 from file1.  The -f
     option produces a similar script, not useful with ed, in the
     opposite order.  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 suffi-
     cient set of file differences.

     Option -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.

FILES
     /tmp/d?????



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DIFF(1-SysV)        RISC/os Reference Manual         DIFF(1-SysV)



     /usr/lib/diffh for -h

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

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

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

WARNINGS
     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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