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| Chapter 2 UNIX Commands |

## diffmk

    /usr/ucb/diffmk oldfile newfile markedfile

A useful program for reviewing changes between drafts of a document. diffmk compares two versions of a file (`oldfile` and `newfile`) and creates a third file (`markedfile`) that contains troff "change mark" requests. When `markedfile` is formatted with nroff or troff, the differences between the two files will be marked in the margin (via the .mc request). diffmk uses a `|` to mark changed lines and a `*` to mark deleted lines. Note that change marks are produced even if the changes are inconsequential (e.g., extra blanks, different input line lengths).

### Example

To run diffmk on multiple files, it's convenient to set up directories in which to keep the old and new versions of your files, and to create a directory in which to store the marked files:

>     $ mkdir OLD NEW CHANGED

Move your old files to OLD and your new files to NEW. Then use this rudimentary Bourne shell script:

>     $ cat do.mark
>     for file
>     do
>     echo "Running diffmk on $file ..."
>     diffmk ../OLD/$file $file ../CHANGED/$file
>     done

You must run the script in the directory of new files:

>     $ cd NEW
>     $ do.mark Ch*

Reference: diff3 |  | Reference: dircmp