Tilted Forum Project Discussion Community - Sheel Script redirection tip

Hi,

Note: this tip is about redirecting output to a file and the screen at the same time. The original 'hack' has been replaced by a much better solution. See the second post!

I'm leaving my 'hack' as an odd example of the many ways problems can be solved.

I justed wanted to share this neat 'hack' I figured out:

To redirect output to a file, but still see it on screen at the same time, use this construct:

Code:

#!/bin/bash

OUPUTFILE=~/output.txt

some_long_command >$OUTPUTFILE &

tail -f $OUTPUTFILE

The idea being:
You want to see the output of a command, but you also want to keep it as reference.

The code below would do this as well, but if the 'command' took a long time you'd be staring at an empty line during execution.

Code:

# this works but is not usable for commands

# that have a long execution time.

command > output_file

cat output_file

I run Gentoo Linux, and emerge's take a relatively long time, so I want to see the output to wether all is well. But in the future I might also want to read back the output to see what warnings etc it might have given.

I'm planning on writing a mother-script around 'emerge' that appears the same as the regular 'emerge' (with it's screen output), but also keeps rotating logs of the results. This construction lets me do that.

NOTES:
- I couldn't find an "output splitter" that redirects output to two places (ie screen and file) or that would've been better.
- Over slow network connections Tail seriously lags behind the actual running of the script, and is very 'jumpy' in its output.
- The above code is not executable, as I'm not presenting a specific situation in it. Simple examples could be easily made however.
- I hope this tip helps someone and/or interests them in scripting for themselves!