Diffing Files to a File


diffmerge {-d=diffoutput} [-u] [-i] {file1} {file2}

Compare 2 files and write the differences to a file (without opening a window).

DiffMerge will use the Ruleset settings and the file suffixes to try to automatically select a Ruleset; if it cannot automatically pick one, DiffMerge will fall-back to the Default Ruleset.

DiffMerge will use the Ruleset's settings from the Character Encoding, Lines to Omit, and Line Handling Pages. When appropriate, it will use the last interactively selected tab size.

Since the output will be reported in lines, the Detail Level and the Ruleset's settings on the Content Handling Page are not relevant.


-d, -diff=pathname

Compare 2 files and write the results to this pathname. The file is only created if there are differences to report.

-u, -unified

If there are differences, write them in Unified Format rather than Tranditional Format.

-i, -ignore_unimportant

Suppress "Unimportant" changes by enabling "Hide Unimportant". Note that this feature can cause the reported diffs to appear slightly differently which may confuse programs like "patch". So it is best to only use this option for personal use.

Exit Status

When diffing files to a file, DiffMerge sets the exit status to:

0:   IDENTICAL - the input files are identical (and the output file is not created).

1:   DIFFERENT - the input files are different (and the differences are written to the output file).

2:   FILE-ERROR - there were file errors that prevented the files from being compared; this includes file I/O errors and problems detecting the character encoding of the input files.

3:   SYNTAX-ERROR - there were syntax errors with the command line arguments.