editdiff

editdiff script1 script2

script1
    The first `ed` script. This script is considered the 'original' state.

script2
    The second `ed` script. This script represents the 'target' state after applying changes from the first script.

The editdiff command compares two `ed` style edit scripts and produces a simplified script that can transform the file described by the first script into the file described by the second. It is particularly useful when you have applied a series of edits to a file, and need a concise way to recreate the combined effect of those edits on another copy of the original file. The resulting script can be applied using `ed` or `red` to efficiently update a file to the state represented by the second script. This command effectively finds the minimal 'difference' or delta between the two sets of changes, rather than comparing the final state of the files after the scripts are applied.

editdiff only works with `ed` style edit scripts. It doesn't handle general file diffs and cannot interpret diffs produced by other tools like `diff` or `patch`. The scripts must be valid `ed` commands. If the scripts are not valid or compatible, editdiff's output might be incorrect or unusable.

Suppose you have two `ed` scripts, `script1.ed` and `script2.ed`. `script1.ed` contains the changes needed to create file 'A' from the original. `script2.ed` contains the changes to create file 'B' from the original. editdiff script1.ed script2.ed will output a new `ed` script, which, when applied to file 'A', will produce file 'B'.

editdiff has been available as part of standard Unix distributions, and later GNU coreutils, for a long time. Its development history mirrors that of other coreutils, focusing on bug fixes and portability. It was initially designed to simplify the process of distributing updates to text files in the era before robust diffing and patching tools were widely available. The usage has waned with the emergence of tools like `diff` and `patch`, but editdiff remains a useful tool for specific scenarios involving `ed` style scripts.

ed(1), red(1)