Rm

Short for remove. Seriously, be careful when using this. There is no undelete once you've unlinked a file unless you've aliased rm to a mv script that moves files to a trash folder. This practice is not recommended because you will eventually find yourself on a system that doesn't have that alias and make a mistake. However, you can alias a different command to do this task by putting something like this in your startup file:

alias del "mv */! .trash"

Common flags

-r recursive -- same as -R
-f force -- do it and damn the consequences
-d directories
-i confirm before delete
-P overwrite files (with 0xFF's, 0x00's, and 0xFF's again) before deleting them
-v be verbose

About the -P argument

Use this argument with extreme care! If you use rm -P to remove a file that has hard links, the file will be immediately overwritten and its contents will be lost, thus not accessible via the links. For example :

$ echo 'Hello World' > foo
$ ln -h foo bar
$ cat foo bar
Hello World
Hello World
$ rm -P foo
$ cat bar
$ Hey !! where is bar contents ??
Hey, command not found

See also rmdir