tee command

[SSP_1]

Hi,

If I try "tar -cvf /dev/rmt/1mn home opt | tee /backuplogs/bkp1.log" , system is not creating the log file. It is only displaying the o/p on screen.

What may be the possible reasons?

[Robin Wakefield · Accepted solution]

Hi,

The output of tar goes to stderr, so you need:

tar -cvf /dev/rmt/1mn home opt 2>&1 | tee /backuplogs/bkp1.log

Rgds, Robin

[Simon Abbott]

Hello,

It would appear that tar outputs it verbose text to standard error. Try the same command with
tar cvf tarfile file 2> logfile
Obviously this doen't help you with tee. A look at the man page for tee doesn't give any indication that you can use it with standard error, only standard out.

Regards,

Simon.

[Duncan Edmonstone]

Thats cos the output from tar is going to stderr, not stdout - try this:

tar -cvf /dev/rmt/1mn home opt 2>&1 | tee /backuplogs/bkp1.log

HTH

Duncan

[SSP_1]

what does 2>&1 mean?
2=stderr & 1=stdoutput right? then what does "2>&1" will do?

[Wim Rombauts]

Because the output from tar is sent to standard error and tee reeds from standard output.

You need to redirect the tar ouput : tar cvf /dev/rmt/1mn home opt 2>&1 | tee ...

[Wim Rombauts]

"2>&1" tells the shell to redirect all output that normally would be sent to file descriptor 2 (standard error) to file descriptor 1 (standard output).
Normal output and errors are sent to two different file descriptors so that you can distinguish between them in a script. Normally filedescriptors 1 and 2 are both set to your display.

[Deepak Extross]

2>&1 means "send stderr (2) to wherever stdout (1) is being output"

[Robin Wakefield]

Hi,

2>&1 simply means file descriptor 2 (stderr) is a duplicate of file descriptor 1 (stdout), in other words stderr is sent out as if it were stdout.

Rgds, Robin

[SSP_1]

thanks a lot all.
I am able to come out of it.