Redirect all output to file in Bash [duplicate]

Question

I know that in Linux, to redirect output from the screen to a file, I can either use the > or tee. However, I'm not sure why part of the output is still output to the screen and not written to the file.

Is there a way to redirect all output to file?

Answer 1

All POSIX operating systems have 3 streams: stdin, stdout, and stderr. stdin is the input, which can accept the stdout or stderr. stdout is the primary output, which is redirected with >, >>, or |. stderr is the error output, which is handled separately so that any exceptions do not get passed to a command or written to a file that it might break; normally, this is sent to a log of some kind, or dumped directly, even when the stdout is redirected. To redirect both to the same place, use:

$command &> /some/file

EDIT: thanks to Zack for pointing out that the above solution is not portable--use instead:

$command > file 2>&1  

If you want to silence the error, do:

$command 2> /dev/null 

Answer 2

That part is written to stderr, use 2> to redirect it. For example:

foo > stdout.txt 2> stderr.txt 

or if you want in same file:

foo > allout.txt 2>&1 

Note: this works in (ba)sh, check your shell for proper syntax