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ysap
Asked: 2012-03-10 06:22:40 +0800 CST

How to diff multiple files across directories?

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I am trying to find diffs between all files of same names across two copies of a directory (say a working and a backup). For example, I can diff two files of same name in both:

> diff d1/f.cpp d2/f.cpp

or I can find differences across the directories:

> diff d1 d2

but how can I find differences between the *.cpp files only?

> diff d1/*.cpp d2/*.cpp

does not seem to work (for obvious reasons).

[It is probably easy to solve with loops, but I am trying to find a more elegant way]

10.04 diff

4 Answers

  1. diff -qr {DIR1} {DIR2} does all files in both directories.

    • q shows only differences
    • r does recursive. Leave it out if you do not need that

    You can not tell diff directly to use wildcards but you can add:

    -x PAT  --exclude=PAT
    Exclude files that match PAT.

-X FILE    --exclude-from=FILE
   Exclude files that match any pattern in FILE.

    to exclude files. So if you only want *.cpp the easiest method is to create a textfile that lists all the files that are not *.cpp. You can do this with the following command: ls -I "*.cpp" > excluded_files where the -I "*.cpp" argument ignores all the .cpp files. Note that the quotation marks are necessary.

    • 62
  2. Best Answer

    You can use a shell loop that runs diff for each file, though this will not catch the cases where d2 contains a file, but d1 doesn't. It might be sufficient though.

    for file in d1/*.cpp; do
    diff "$file" "d2/${file##*/}"
done

    Or all on one line:

    for file in d1/*.cpp; do diff "$file" "d2/${file##*/}"; done

    The ${file##*/} part is a special parameter expansion.

    If the file variable contains d1/hello.cpp, then "${file##*/}" will expand to hello.cpp (the value of file, but with everything up to, and including, the last / removed).

    So "d2/${file##*/}" will result in d2/hello.cpp and the resulting diff command is thus diff d1/hello.cpp d2/hello.cpp

    See http://mywiki.wooledge.org/BashFAQ/100 for more on string manipulations in bash.

    On a side note, a version control system (such as subversion, git, mercurial etc...) would make this type of diffing much easier.

    • 17

  3. Some time after asking the question, I found out the meld diff utility, and am using it since then. This is a great piece of GUI based program that makes comparison and merge between files and directory a very easy task. It does two- or three-way compares.

    Specifically, it answers my original question in that it shows you a color-coded comparison of the directory contents, and lets you compare specific files by a double-click on the file name.

    If one needs more than a three-way comparison, then gvimdiff (based on the vim editor) is a great too as well that provides this functionality.

    • 6

  4. There's a lightweight solution for that:

    1. Set up this tiny plugin http://www.vim.org/scripts/script.php?script_id=5309
    2. Do diff dir1 dir2 | vim -R - at shell

    It will add folds and side-by-side comparison for changed files.

    • 1