diff3

Compare files

$ diff3 [path/to/file1] [path/to/file2] [path/to/file3]

$ diff3 [[-A|--show-all]] [path/to/file1] [path/to/file2] [path/to/file3]

diff3 [options] file1 file2 file3

-e
    Produce an ed script to merge file2 and file3 into file1.

-x
    Produce an ed script to merge file2 into file1. Ignore differences that are also in file3.

-E
    Produce an ed script to merge file2 into file1.
The differences that are in file3 are bracketed by <<<<<<< and >>>>>>> symbols.

-m
    Merge file2 and file3 into file1, showing conflicts with <<<<<<<, =======, and >>>>>>>.

-i
    Use an intelligent algorithm to match up lines.

-a
    Treat all lines as changed, forcing a complete remerge.

-A
    Similar to -m, but also includes common lines between the three files in the output.

-T
    When using -m, include the original file names in the conflict markers.

-3
    Consider overlaps (useful for overlapping merges).

-L label
    Use 'label' instead of the file name in the conflict markers (with -m).

-d
    Output in diff format.

The diff3 command merges three versions of a file, marking the differences between them.
It's primarily used to resolve conflicts when multiple developers have modified the same file independently.
The command compares the first file against the second and third files, reporting areas where they differ. These differences are presented in a format that allows users to identify and resolve conflicting changes. Unlike simple two-way diff utilities, diff3 helps resolve intricate merging scenarios where the original file has been branched into multiple versions.
The output can be configured to display overlapping changes, allowing users to understand how changes interact. diff3 is particularly valuable in collaborative software development environments. The command supports several options to control the format of the output and how conflicts are resolved.
While powerful, manual inspection and intervention are usually needed to produce a fully merged and correct output.

Resolving complex conflicts with diff3 often requires manual intervention and careful examination of the changes.
The ed script output can be difficult to understand for novice users.

The default output of diff3 identifies regions of difference between the three input files.
It highlights overlapping and non-overlapping changes, using markers to indicate the source of each change.
Understanding this output is crucial for resolving conflicts.

The choice of merge strategy (e.g., using '-e', '-m', or '-A') depends on the complexity of the changes and the desired level of automation.
Some strategies are better suited for simple conflicts, while others provide more detailed information for manual resolution.

diff3 has been a part of Unix-like systems for a long time, originating in the early days of software development when collaborative coding was becoming more common. It addresses the problem of merging divergent versions of files, providing a mechanism to identify and resolve conflicts arising from parallel development. Over time, it has been refined and adapted to different environments, becoming a standard tool for managing code changes.

diff(1), patch(1)