How to diff multiple files across directories?

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.

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.

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.