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Redirect STDOUT & STDERR to file and then on screen


 
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# 1  
Old 09-25-2018
Redirect STDOUT & STDERR to file and then on screen

Dear all,
redirecting STDOUT & STDERR to file is quite simple, I'm currently using:
Code:
Code:
exec 1>>/tmp/tmp.log; exec 2>>/tmp/tmp.log

But during script execution I would like the output come back again to screen, how to do that?

Thanks
Luc

Moderator's Comments:
Mod Comment edit by bakunin: please use CODE-tags like the ones i edited in for you. Thanl you.

Last edited by bakunin; 09-25-2018 at 06:33 PM..
# 2  
Old 09-25-2018
Do you really want to capture ALL remaining session? Above execs aren't necessarily the killall tool for what you need. Howsoever, did you consider teeing output to /dev/tty?
# 3  
Old 09-25-2018
You will need to restore file descriptors to their original values.
This can be done from inside the script in point of code you like.

During runtime, outside of the script, possibly with some gdb hackery, but i would advise against it.

Example for both operations can be found by searching keywords above.

Hope that helps.
Regards
Peasant.
# 4  
Old 09-25-2018
One file descriptor can't write to two streams by itself. You'll need tee or something else to accomplish this.
# 5  
Old 09-25-2018
I usually use this paradigm at the top of a script:
Code:
# Redirect the stdout/stderr to screen AND log file

mkfifo /tmp/$$-err /tmp/$$-out
# to merge stdout/stderr to log file AND screen
( exec tee -a ${FILE_LOG} </tmp/$$-out ) &
( exec tee -a ${FILE_LOG} </tmp/$$-err >&2 ) &

exec 1>/tmp/$$-out
exec 2>/tmp/$$-err
rm -f /tmp/$$-out /tmp/$$-err


Last edited by vgersh99; 09-25-2018 at 06:58 PM..
This User Gave Thanks to vgersh99 For This Post:
# 6  
Old 09-25-2018
Quote:
Originally Posted by vgersh99
I usually this paradigm at the top of a script:
That is a really clever way to do it. I will shamelessly steal that immediately and include it into my own scripts. Thank you!

bakunin
This User Gave Thanks to bakunin For This Post:
# 7  
Old 09-26-2018
Quote:
exec 1>>/tmp/tmp.log; exec 2>>/tmp/tmp.log
Two file handles for the same file? I guess this can loose some previous writes when switching to the other handle.
Correct is
Code:
exec 1>>/tmp/tmp.log 2>&1


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