Is there a command that makes another command "in-place"?

Question

I find myself trying to "edit" a file in-place quite a lot in my shell. Say, I want to remove all lines in words.txt that contain the letter e. Then, I would execute:

$ grep -v e words.txt > words-without-e.txt
$ mv words-without-e.txt words.txt

Many people are confused why they are left with an empty file when executing the following (I am not):

$ grep -v e words.txt > words.txt
grep: words.txt: input file is also the output

Some commands have special flags for in-place behaviour, like --in-place (see sed(1)) to allow this. It's possible to use sponge(1), but this requires me to type the file name twice, which I don't like.

$ grep -v e words.txt | sponge words.txt

I have defined a function that I find handy:

function inplace { "${@:2}" < "$1" | sponge $1 }

With it, I can now do:

$ inplace words.txt grep -v e

I know that this is limited to "stream processing", i.e. commands that take standard input, process it, and produce standard output. But many commands do.

Maybe I looked in the wrong places, but I haven't stumbled across a similar definition yet, especially given how often the question about in-place editing comes up.

• Is there a common utility that serves the same purpose?
• Have you defined such a function? How does your definition look like? What did you call it?
• Why does this not come up more often? Or did I just miss it?

Answer 1

As far as I know, there isn't a generic utility that can make any command work in-place.

Usually, when people want to programatically edit files in-place, they use sed or perl with -i parameter.

Probably that's the reason why this topic does not come up often - contrary to what you may think, it is not so much needed if there are utilities that can edit files in-place.