Sometimes it can be handy to get a quick diff of the changes that have been made to the current buffer since the previous save. This can be achieved with a simple command-line mode command.
To demonstrate, let's start with the following buffer:
Now lets edit the buffer. To keep it simple we will make a single edit, changing "two" to "changed":
Now, we can generate a simple diff with the command:
:write !diff % -
Let's review what this does. To start, this uses the :write command with the following call signature:
:w[rite] !{cmd}
Which passes the entire contents of the current buffer to the specified command via
stdin. In this example we will use the diff shell command, which has the call
signature:
diff file1 file2
where our command defines file1 and file2 as:
-
file1 =
%, which contains the filename of the current file, and -
file2 =
-, which tells diff to read stdin
So, putting this all together, we pass the current buffer contents to the diff command, and
generate the diff between the saved version of the current file (%) and the current buffer
contents. Finally, the diff is passed back to Neovim:
The output window shows that the line containing "two" has been changed to "changed". diff also returns a status code if 1, meaning that the two files were different.
This is definitely not the prettiest diff in the world, but is useful when a quick diff is required. Take a look at:
diff --help
to see what options are available to suit the output to your needs. For example, by leveraging
diff's options one can format the same output as a side-by-side diff:
:write !diff -yt -W 60 % -