stderr + logging and exit status

Rasna · 06-06-2013, 04:26 AM

How to get a shell commands stderr to screen and also to a log file and the exit status of the command (that is $?).
Any idea how to get all these?
I tried "command 2>&1 | tee error.log"
but that time I didnt get the echo $? status properly!

Thanks in advance
Rasna

shivaa · 06-06-2013, 06:15 AM

If you want to show stderr on screen then don't redirect it to any file. And $? will give you exit status of last command run, so explain it little more that what exactly you did.
Also take a note that, 2>&1 will redirect sterr as well stdout to specified file, so if you just want to redirect stderr, then use only 2 > filename.

Rasna · 06-06-2013, 06:48 AM

Hi,
actual concern is,
I wanted to print the stderr of the command execution and also wanted to compare this with an expected "message".
so actual flow will be
> check for the command exist status (using $?)
> then if exit status is not zero , I need to check for the expected "message" in the stderr and return this case differently.[Here stderr needed to be printed to the screen also]

my logic is:
>command 2>error.log
>if $? is not zero will do cat of error.log and then do grep for the "message" in error.log

shivaa · 06-06-2013, 08:08 AM

As said previously, without seeing the script, it's not easy to predict that what you want to do. However, you can try in following way:

Code:

#!/bin/bash
command 2> error.log
if [ $? -ne 0 ] ; then
cat error.log | grep <error_msg>  ## grep error message if exit status of previous cmd is not 0.
fi

rtmistler · 06-06-2013, 08:12 AM

Anything you can write in a script file you can send to the command line, they are the same thing.

So you can type

Code:

ls; if [ $? -eq 1 ]; then echo "ERROR"; fi; exit

in the command line, or you can write that in a script.

However you're doing this, you can place an "if" statement in there to evaluate the command result.