Bourne shell tips

My preferred Unix shell is bash; if that's not available, I'll use zsh, ash, ksh or plain sh. I really don't like csh or tcsh very much at all; they make it difficult to write scripts at the prompt (and shouldn't be used for non-interactive scripting at all; see Tom Christiansen's "Csh Programming Considered Harmful" for an impassioned rant on why this is a bad idea). My Linux system doesn't have a /bin/csh, and I haven't missed it yet.

rc is another nice shell, based on the Plan 9 shell. Its syntax and features are better suited to programming than the Bourne shell.

For more bash tips, have a look at deadman.org's bash tips page.

If you're renaming a file with a long filename where the change is small, you can use {} to your advantage:
mv /some/long/name/{oldfile,newfile}
mv /some/long/name/spelt-{u,i}ncorrectly
If you want to do something to every line of a file in bash, you can use a while loop with read, which puts each line into the $REPLY variable:
while read ; do echo $REPLY | sed 's/foo/bar/g' ; done <file
You can also read lines from several files by using multiple file descriptors:
while read a ; do read b <&3 ; echo $a $b ; done <file1 3<file2
Since rmdir only works on empty directories, you can use rmdir * to prune empty directories that are in the current directory.