strace -f -p pid_no > trace.txt 2>&1

threezerous · 04-09-2010, 08:19 AM

I was given the above command to trace one of the java processes which was failing with an outofmemory exception.

Based on man I under stand what -f and -p stand for. I also understand redirect output to trace.txt. But I am not clear on what '2>&1' is for. This has successfully run and helped me debug some issues. Can somebody explain what is the significance of '2>&1' is?

Thanks

rayfordj · 04-09-2010, 08:28 AM

2 is stderr, 1 is stdout

you are effectively saying send/redirect stderr (2) to the same location as stdout (1)

All About Redirection

you might also be interested in the use of strace's output to a file option...

Code:

strace -f -p pid_no -o trace.txt

threezerous · 04-09-2010, 09:47 AM

Thanks for helping understand redirection. Also the second command is easier to remember