How do I create use the patch command to make sure two file are identical?

  • Also see:
    Man page for patch.

    We start off with two demo files. fileb is our changed file, we want filea to be the same as fileb.

    $ cat filea
    Shell scripting is foun
    $ cat fileb
    Shell scripting is fun

    Create a file of differences, using diff.

    $ diff -c file[ba] > file.changes

    The file.changes file looks like this.

    $ cat file.changes
    *** filea       2020-11-17 11:55:16.364702950 -0800
    --- fileb       2020-11-17 11:55:19.688756600 -0800
    *** 1 ****
    ! Shell scripting is foun
    --- 1 ----
    ! Shell scripting is fun

    Let's patch filea with the changes of fileb.

    $ patch -c filea file.changes
    patching file filea

    To verify.

    $ cat filea
    Shell scripting is fun

    This is an alternative to cut & paste, where many a mistake can be made, extra spaces, blank lines. Of course you can copy and paste and then do you diffs too.

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