NAME

SYNOPSIS

    use Text::Diff;

    ## Mix and match filenames, strings, file handles, producer subs,
    ## or arrays of records; returns diff in a string.
    ## WARNING: can return B<large> diffs for large files.
    my $diff = diff "file1.txt", "file2.txt", { STYLE => "Context" };
    my $diff = diff \$string1,   \$string2,   \%options;
    my $diff = diff \*FH1,       \*FH2;
    my $diff = diff \&reader1,   \&reader2;
    my $diff = diff \@records1,  \@records2;

    ## May also mix input types:
    my $diff = diff \@records1,  "file_B.txt";

DESCRIPTION

Relies on Algorithm::Diff for, well, the algorithm. This may not produce the same exact diff as a system's local "diff" executable, but it will be a valid diff and comprehensible by "patch". We haven't seen any differences between Algorithm::Diff's logic and GNU "diff"'s, but we have not examined them to make sure they are indeed identical.

Note: If you don't want to import the "diff" function, do one of the following:

   use Text::Diff ();

   require Text::Diff;

That's a pretty rare occurrence, so "diff()" is exported by default.

If you pass a filename, but the file can't be read, then "diff()" will "croak".

OPTIONS

FILENAME_A, MTIME_A, FILENAME_B, MTIME_B

The name of the file and the modification time "files".

These are filled in automatically for each file when "diff()" is passed a filename, unless a defined value is passed in.

If a filename is not passed in and FILENAME_A and FILENAME_B are not provided or are "undef", the header will not be printed.

Unused on "OldStyle" diffs.

OFFSET_A, OFFSET_B

The index of the first line / element. These default to 1 for all parameter types except ARRAY references, for which the default is 0. This is because ARRAY references are presumed to be data structures, while the others are line-oriented text.

STYLE

"Unified", "Context", "OldStyle", or an object or class reference for a class providing "file_header()", "hunk_header()", "hunk()", "hunk_footer()" and "file_footer()" methods. The two footer() methods are provided for overloading only; none of the formats provide them.

Defaults to "Unified" (unlike standard "diff", but Unified is what's most often used in submitting patches and is the most human readable of the three.

If the package indicated by the STYLE has no "hunk()" method, "diff()" will load it automatically (lazy loading). Since all such packages should inherit from "Text::Diff::Base", this should be marvy.

Styles may be specified as class names ("STYLE => 'Foo'"), in which case they will be "new()"ed with no parameters, or as objects ("STYLE => Foo->new").

CONTEXT

How many lines before and after each diff to display. Ignored on old-style diffs. Defaults to 3.

OUTPUT

Examples and their equivalent subroutines:

    OUTPUT   => \*FOOHANDLE,   # like: sub { print FOOHANDLE shift() }
    OUTPUT   => \$output,      # like: sub { $output .= shift }
    OUTPUT   => \@output,      # like: sub { push @output, shift }
    OUTPUT   => sub { $output .= shift },
    

If no "OUTPUT" is supplied, returns the diffs in a string. If "OUTPUT" is a "CODE" ref, it will be called once with the (optional) file header, and once for each hunk body with the text to emit. If "OUTPUT" is an IO::Handle, output will be emitted to that handle.

FILENAME_PREFIX_A, FILENAME_PREFIX_B

The string to print before the filename in the header. Unused on "OldStyle" diffs. Defaults are "---", "+++" for Unified and "***", "+++" for Context.

KEYGEN, KEYGEN_ARGS

These are passed to "traverse_sequences" in Algorithm::Diff.

Note: if neither "FILENAME_" option is defined, the header will not be printed. If at least one is present, the other and both "MTIME_" options must be present or "Use of undefined variable" warnings will be generated (except on "OldStyle" diffs, which ignores these options).

Formatting Classes

Each class has "file_header()", "hunk_header()", "hunk()", and "footer()" methods identical to those documented in the "Text::Diff::Unified" section. "header()" is called before the "hunk()" is first called, "footer()" afterwards. The default footer function is an empty method provided for overloading:

    sub footer { return "End of patch\n" }

Some output formats are provided by external modules (which are loaded automatically), such as Text::Diff::Table. These are are documented here to keep the documentation simple.

  --- A   Mon Nov 12 23:49:30 2001
  +++ B   Mon Nov 12 23:49:30 2001
  @@ -2,13 +2,13 @@
   2
   3
   4
  -5d
  +5a
   6
   7
   8
   9
  +9a
   10
   11
  -11d
   12
   13

  +--+----------------------------------+--+------------------------------+
  |  |../Test-Differences-0.2/MANIFEST  |  |../Test-Differences/MANIFEST  |
  |  |Thu Dec 13 15:38:49 2001          |  |Sat Dec 15 02:09:44 2001      |
  +--+----------------------------------+--+------------------------------+
  |  |                                  * 1|Changes                       *
  | 1|Differences.pm                    | 2|Differences.pm                |
  | 2|MANIFEST                          | 3|MANIFEST                      |
  |  |                                  * 4|MANIFEST.SKIP                 *
  | 3|Makefile.PL                       | 5|Makefile.PL                   |
  |  |                                  * 6|t/00escape.t                  *
  | 4|t/00flatten.t                     | 7|t/00flatten.t                 |
  | 5|t/01text_vs_data.t                | 8|t/01text_vs_data.t            |
  | 6|t/10test.t                        | 9|t/10test.t                    |
  +--+----------------------------------+--+------------------------------+

  +--+--------------------------+--------------------------+
  |  |demo_ws_A.txt             |demo_ws_B.txt             |
  |  |Fri Dec 21 08:36:32 2001  |Fri Dec 21 08:36:50 2001  |
  +--+--------------------------+--------------------------+
  | 1|identical                 |identical                 |
  * 2|        spaced in         |        also spaced in    *
  * 3|embedded space            |embedded        tab       *
  | 4|identical                 |identical                 |
  * 5|        spaced in         |\ttabbed in               *
  * 6|trailing spaces\s\s\n     |trailing tabs\t\t\n       *
  | 7|identical                 |identical                 |
  * 8|lf line\n                 |crlf line\r\n             *
  * 9|embedded ws               |embedded\tws              *
  +--+--------------------------+--------------------------+

    *** A   Mon Nov 12 23:49:30 2001
    --- B   Mon Nov 12 23:49:30 2001
    ***************
    *** 2,14 ****
      2
      3
      4
    ! 5d
      6
      7
      8
      9
      10
      11
    - 11d
      12
      13
    --- 2,14 ----
      2
      3
      4
    ! 5a
      6
      7
      8
      9
    + 9a
      10
      11
      12
      13

    5c5
    < 5d
    ---
    > 5a
    9a10
    > 9a
    12d12
    < 11d

LIMITATIONS

Does not provide most of the more refined GNU "diff" options: recursive directory tree scanning, ignoring blank lines / whitespace, etc., etc. These can all be added as time permits and need arises, many are rather easy; patches quite welcome.

Uses closures internally, this may lead to leaks on Perl versions 5.6.1 and prior if used many times over a process' life time.

SEE ALSO

YAML::Diff - find difference between two YAML documents.

HTML::Differences - find difference between two HTML documents. This uses a more sane approach than HTML::Diff.

XML::Diff - find difference between two XML documents.

Array::Diff - find the differences between two Perl arrays.

Hash::Diff - find the differences between two Perl hashes.

Data::Diff - find difference between two arbitrary data structures.

REPOSITORY

AUTHOR

Barrie Slaymaker <barries@slaysys.com>

COPYRIGHT

Copyright 2001 Barrie Slaymaker. All Rights Reserved.

You may use this under the terms of either the Artistic License or GNU Public License v 2.0 or greater.