Ubuntu – Direct output from a command to a file including the original command, AND print in terminal

command line

When running some tests, I need to run a series of commands. It would be extremely useful to me, and save me a lot of time, if there was a way to do all of these things:

  • Run the command I need to run
  • Redirect all the output from the command to a specified file
  • Include the original command in the specified file
  • Print the output from the original command in the terminal

People have suggested using tee to me which does a great job of printing to terminal as well as sending to a file but doesn't include the original command. What I'd like to end up with is a file where the first line is the command I ran, and then below that is the output from the command.

Someone suggested this:

echo "ls -l" | xargs -I{} bash -c "echo >> output.file; eval {} >> output.file"

But this doesn't either print the output in the terminal or include the original command in the file.

I'd appreciate any ideas.

Best Answer

That's tee you're searching for.

ls -l | tee outfile

prints the output of ls -l to stdout (i.e. the terminal) and saves it in the file outfile at the same time. But: It doesn't write the command name neither to stdout nor to the file. To achieve that, just echo the command name before running the command and pipe both outputs to tee:

( echo "ls -l" && ls -l ) | tee outfile

That's cumbersome to type, so why not define a function?

both(){ ( echo "$@" && "$@" ) | tee outfile ;}

After that you can just run

both ls -l

to get the desired result. Put the function in your ~/.bashrc to have it defined in every new terminal.

If you want to be able to specify the output file as the first argument like in

both output ls -l

instead make it:

both(){ ( echo "${@:2}" && "${@:2}" ) | tee "$1" ;}

If you don't want the output file to be overwritten but rather append to it, add the -a option to tee.

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