Ever wanted to do a diff between a local file and a remote one? I have, so I wrote a simple shell script that'll do it for you. It requires scp, diff, and rm to be available on your system, which should be the case on any modern *nix. The -b option to diff tells it to ignore white-space difference. If you don't have password-less SSH authentication set up, you'll want to remove the >& /dev/null trailers from the two scp lines so you get your prompts.
To run, just drop this into /usr/bin (or somewhere else on your path), make it executable, and call it just like diff, except with scp-compatible file paths.
#!/bin/sh # # this acts as a remote diff program, accepting two files and displaying # a diff for them. Zero, one, or both files can be remote. File paths # must be in a format `scp` understands: [[user@]host:]file if [ "$1" = "" -o "$2" = "" ]; then echo "Usage: `basename $0` file1 file2" exit 1 fi scp $1 rdiff.1 >& /dev/null scp $2 rdiff.2 >& /dev/null diff -b rdiff.1 rdiff.2 rm -f rdiff.1 rdiff.2
Update: Horst and Amit both posted a far better solution that leverages SSH directly. Back when I wrote this I didn't appreciate SSH's power for more than interactive shells. Here's his command (replaced the brace-wrapped strings as needed):
ssh {remote_host} cat {remote_file} | diff {local_file} -
Great script, thanks a lot!
this will happily overwrite the two files "rdiff.1″ and "rdiff.2″, should they exist in the current directory.
if you really want to diff a _local_ file and a remote one, use something like
ssh remotehost 'cat remotefile' | diff – localfile
…and you don't have to worry about how to create good temporary files
horst,
You are right, of course. A much better way to do it. I seem to be constantly forgetting how darn versatile ssh is: so much more than just a secure shell.
What I actually have to write, and soon, is a remote *recursive* diff. Write it, or find one (which is how I got here :)
For recursive diff, you could try using nfs, and pretend they are both local. Obviously using –recursive with diff :-)
NFS wont be so great with your transit costs if you have lots of large files though. Great for LAN environments! – -
Recursive remote diff?? Aren't we getting into svn/cvs at that point :)
I think it's worth to add option to pass diff option
if [ $3 = "" ]
then
opt="-b"
else
opt=$3
fi
The simplest way to do remote diff is as follows:
ssh {remote_host} cat {remote_file} | diff {local_file} -
@Amit
That is definitely a better solution. In my defense, when I posted this (3.5 years ago) I didn't "get" that `ssh` could be anything more than a secure remote interactive shell. I've since learned better. : )
That was a solution suggested to me by my Perl/Unix instructor, the revered Dr. Tim Maher. The beauty of it is that it cleans up after itself.
A bit tweaked version of your script:
http://larryn.blogspot.com/2009/01/remote-diff.html