bash - automatically capture output of last execut

Question

I'd like to be able to use the result of the last executed command in a subsequent command. For example,

$ find . -name foo.txt
./home/user/some/directory/foo.txt

Now let's say I want to be able to open the file in an editor, or delete it, or do something else with it, e.g.

mv <some-variable-that-contains-the-result> /some/new/location

How can I do it? Maybe using some bash variable?

Update:

To clarify, I don't want to assign things manually. What I'm after is something like built-in bash variables, e.g.

ls /tmp
cd $_

$_ holds the last argument of the previous command. I want something similar, but with the output of the last command.

Final update:

Seth's answer has worked quite well. Couple of things to bear in mind:

• don't forget to touch /tmp/x when trying the solution for the very first time
• the result will only be stored if last command's exit code was successful

Answer 1

If all you want is to rerun your last command and get the output, a simple bash variable would work:

LAST=`!!`

So then you can run your command on the output with:

yourCommand $LAST

This will spawn a new process and rerun your command, then give you the output. It sounds like what you would really like would be a bash history file for command output. This means you will need to capture the output that bash sends to your terminal. You could write something to watch the /dev or /proc necessary, but that's messy. You could also just create a "special pipe" between your term and bash with a tee command in the middle which redirects to your output file.

But both of those are kind of hacky solutions. I think the best thing would be terminator which is a more modern terminal with output logging. Just check your log file for the results of the last command. A bash variable similar to the above would make this even simpler.

Answer 2

find . -name foo.txt 1> tmpfile && mv `cat tmpfile` /path/to/some/dir/

is yet another way, albeit dirty.

Answer 3

I don't know of any variable that does this automatically. To do something aside from just copy-pasting the result, you can re-run whatever you just did, eg

vim $(!!)

Where !! is history expansion meaning 'the previous command'.

If you expect there to be a single filename with spaces or other characters in it that might prevent proper argument parsing, quote the result (vim "$(!!)"). Leaving it unquoted will allow multiple files to be opened at once as long as they don't include spaces or other shell parsing tokens.

Answer 4

Bash is kind of an ugly language. Yes, you can assign the output to variable

MY_VAR="$(find -name foo.txt)"
echo "$MY_VAR"

But better hope your hardest that find only returned one result and that that result didn't have any "odd" characters in it, like carriage returns or line feeds, as they will be silently modified when assigned to a Bash variable.

But better be careful to quote your variable correctly when using it!

It's better to act on the file directly, e.g. with find's -execdir (consult the manual).

find -name foo.txt -execdir vim '{}' ';'

or

find -name foo.txt -execdir rename 's/\.txt$/.xml/' '{}' ';'

Answer 5

This is a really hacky solution, but it seems to mostly work some of the time. During testing, I noted it sometimes didn't work very well when getting a ^C on the command line, though I did tweak it a bit to behave a bit better.

This hack is an interactive mode hack only, and I am pretty confident that I would not recommend it to anyone. Background commands are likely to cause even less defined behavior than normal. The other answers are a better way of programmatically getting at results.

---

That being said, here is the "solution":

PROMPT_COMMAND='LAST="`cat /tmp/x`"; exec >/dev/tty; exec > >(tee /tmp/x)'

Set this bash environmental variable and issues commands as desired. $LAST will usually have the output you are looking for:

startide seth> fortune
Courtship to marriage, as a very witty prologue to a very dull play.
                -- William Congreve
startide seth> echo "$LAST"
Courtship to marriage, as a very witty prologue to a very dull play.
                -- William Congreve

Answer 6

Capture the output with backticks:

output=`program arguments`
echo $output
emacs $output