tee alternative

nenpa8lo · 01-23-2012, 11:13 AM

I am working with very limited shell (busybox) which has no 'tee' command. Therefore I need an alternative. Task is to print stdout to a file, and stderr to console and the file.
Any ideas?

millgates · 01-23-2012, 11:23 AM

How about a script like this? That's about the simplest thing I can think of right now

Code:

FILENAME='./log'

while read TEMP_LINE; do
	echo "$TEMP_LINE"
	echo "$TEMP_LINE" >> $FILENAME
done

ntubski · 01-23-2012, 01:08 PM

The GNU awk manual has an example of tee in awk:

13.2.5 Duplicating Output into Multiple Files

nenpa8lo · 01-24-2012, 09:56 AM

I think I need some help here...

stdout&stderr ===> debugfile
stderr ===> console

Code:

cmd | tee file.txt

Prints stderr/stdout to the console and stdout to the file. I need to change it so it works like on the image above.

theNbomr · 01-24-2012, 11:04 AM

How about simply rebuilding busybox with tee enabled? Shouldn't add but a few bytes.
--- rod.

gnashley · 01-24-2012, 12:38 PM

I was hoping to see some fancy shell fd re-direction tick here... still hoping, infact.

millgates · 01-24-2012, 12:43 PM

Quote:

Originally Posted by nenpa8lo

I think I need some help here...

stdout&stderr ===> debugfile
stderr ===> console

Code:

cmd | tee file.txt

Prints stderr/stdout to the console and stdout to the file. I need to change it so it works like on the image above.

How about something like this?

Code:

command  3>&1 1>&2 2>&3 | tee file.txt

nenpa8lo · 01-25-2012, 04:05 AM

@millgates It prints stdout to the console and stderr to the console and the logfile. I need it to work the other way round:

stderr+stdout => file
stderr => console

millgates · 01-25-2012, 05:04 AM

Oh, sorry... I seem to have misread your question. How about this then?

Code:

cmd 3>&1 1>>logfile.txt 2>&3 | tee -a logfile.txt

nenpa8lo · 01-25-2012, 05:19 AM

SOLVED! You're the man millgates.

Reuti · 01-26-2012, 03:39 AM

Quote:

Originally Posted by millgates

Code:

cmd 3>&1 1>>logfile.txt 2>&3 | tee -a logfile.txt

Couldn’t it be shortend to:

Code:

cmd 2>&1 >>logfile.txt | tee -a logfile.txt

nenpa8lo · 01-26-2012, 10:51 AM

Both versions work, thanks!
But can you explain me why? How is stderr getting to the console and the file, and normal output to the file?
Thanks

Reuti · 01-26-2012, 11:01 AM

The entries must be read from right to left:

Code:

2>&1

means: copy the file descriptor to which 1 is pointing to 2, i.e. the stderr will go to the stdout. Then the:

Code:

>>logfile.txt

will copy the file descriptor from logfile.txt to 1, i.e. stdout is written to the file. Often it’s used in the reverse order to combine stdout and stderr.

The tee command will then append the original stderr (which is now going via the stdout descriptor) to the file logfile.txt.

Unless there would be a huge delay because of the tee command, there should be no race condition where both redirections will write at the same time to the file.