If I use this
cmd 2>/var/error.log
Then my error goes to that file but then I can't see on screen.
Is there any way I can simultaneously show it on screen as well as send to file?
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2 Answers
This will display both stdout and stderr on the terminal while only sending stderr to err.log:
cmd 2> >(tee err.log >&2)
>(...) is process substitution. (The space between the two consecutive > is essential.) This sends stderr and only stderr to the tee command.
The >&2 causes the error messages remain in stderr. This would be important, for example, if this line occurs inside some script whose stdin or stderr is being redirected. (Hat tip: Chepner.)
3 Comments
John1024
@user3214546 The error output may sometimes, depending on timing, show up late, after the system has written a new prompt. But, if you hit enter, you will see that the system does not attempt to execute the error output. This is because the error output, however it appears, is not really on the command line. You can enter a new command as usual, say
ls, and execute it with no interference from the late output.
chepner
Strictly speaking, you might want to use
>(tee err.log >&2) so that the error messages go back to standard error, rather than standard output. It only makes a difference if the line occurs inside another script which might be redirecting its standard error elsewhere, though.John1024
@chepner Nice improvement! Answer updated to maintain stderr as it should be.
cmd 2>&1 | tee /tmp/error.log
1 Comment
user3214546
But that will send stdout as well in that file , is there any way just to send error output in file