diff is designed to compare two files. You can also compare directories. In this form, bash uses 'process substitution' in place of a file as an input to diff. Each input to diff can be filtered as you choose. I use find and egrep to select the files to compare.

:q to quit

You got some results in two variables within your shell script and would like to find the differences? Changes in process lists, reworked file contents, ... . No need to write to temporary files. You can use all the diff parameters you'll need. Maybe anything like $ grep "^>"

is helpful afterwards.

Handy when you need to create a list of files to be updated when subversion is not available on the remote host. You can take this tar file, and upload and extract it where you need it. Replace M and N with the revisions specific to yours. Make sure you do this from an updated (svn up) working directory.

Simple way to achieve a colored SVN diff

Lists revisions in a Subversion repository with a timestamp that doesn't follow the revision numbering order. If everything is OK, nothing is displayed.

It can be hard to spot differences in reformatted files, because of all the diff noise created by word wrapped lines. This command removes all the noise and performs a word-by-word diff. To ignore empty lines, add -B to the diff command. Also, if this is something you do often, you might want to check out the wdiff(1) program.

This uses Bash's "process substitution" feature to compare (using diff) the output of two different process pipelines.

populate the auth.hosts file with a list of IP addresses that are authorized to be in use and when you run this command it will return the addresses that are pingable and not in the authorized list.

Can be combined with the "Command line Twitter" command to tweet unauthorized access.

I put this in a shell script called "svndiff", as it provides a handy decorated "svn diff" output that is colored (which you can't see here) and paged. The -r is required so less doesn't mangle the color codes.

Sees if two records differ in their entries, irrespective of order.

See which files differ in a diff, and how many changes there are. Very useful when you have tons of differences.

Useful for massive files where doing a full diff would take too long. This just runs diff on the first 500 lines of each. The use of subshells to feed STDIN is quite a useful construct.

get subversion diff output without distracting whitespace changes. good for when you are cleaning up code to make sure you didn't change anything important. also useful when working with old code, or someone else's code.

Use this to make a new commit that "softly" reverts a branch to some commit (i.e. squashes the history into an inverse patch). You can review the changes first by doing the diff alone.

We use this to quickly highlight differences and provide a quick way to cut and paste the command to view the files using the marvellous vimdiff

bash/ksh subshell redirection (as file descriptors) used as input to diff

Useful for checking if there are differences between local and remote files.