Have you ever found yourself copying a Linux file and adding a suffix, like this?
$ cp myfile myfile2
Try this command instead, which does the same thing but with less typing (one argument instead of two):
$ cp myfile{,2}
Why it works: This command employs brace expansion, a feature of certain Linux shells. A comma-separated expression like this:
myfile{1,2,3}
expands to this:
myfile1 myfile2 myfile3
In my example command, the braces enclose two strings: an empty string and a 2. So this expression:
myfile{,2}
expands to:
myfile myfile2
Throw a “cp” or “mv” command at the beginning, and you have the command I suggested:
$ cp myfile{,2}
which expands to:
$ cp myfile myfile2
I learned this empty-string trick from a colleague, Dan Ritter (thanks!), who recommends it when the original filename is very long, so you don’t have to type the name twice:
$ mv very_silly_long_file_name{,.old}
The preceding command expands to:
$ mv very_silly_long_file_name very_silly_long_file_name.old
You’ll find many more tips and techniques in my new book, Efficient Linux at the Command Line.
