Question

I want to backup a file in some-other sub-directory different from my current directory like this:

cp /aaa/bbb/ccc/ddd/eeee/file.sh /aaa/bbb/ccc/ddd/eeee/file.sh.old

As you see both source and dest dir are the same, so common convention would be to change to the common directory, perform the copy im ./, then change back to the original directory.

Is there a single-line command to accomplish the copy in this situation?

Answer 1

Yes. Use this:

cp /aaa/bbb/ccc/ddd/eeee/{file.sh,file.sh.old}

The curly braces will cause the first part of the string to be reused for each of the items separated by commas. Bash is what expands the above into two separate paths and then passes it to cp. To see what Bash would be passing to cp, simply add an echo to the beginning:

echo cp /aaa/bbb/ccc/ddd/eeee/{file.sh,file.sh.old}

You will see that produces your original statement:

cp /aaa/bbb/ccc/ddd/eeee/file.sh /aaa/bbb/ccc/ddd/eeee/file.sh.old

You’re just using a Bash trick to save on typing.