Need a way to temporarily redirect STDOUT

I know how to redirect output in Linux. Thing is, I have alot of output in my bash script and I don't want to type something like

echo $foo >> bar


over and over again. I would much rather do something like:

hey, bash, for the time being put all your STDOUT in "bar"
echo $foo
.
.
OK, bash, you can go back to regular STDOUT now


I tried opening FD 1 as a file:

exec 1>bar


but couldn't get STDOUT back to normal when I was done. Closing the file

exec 1>&-


gave me errors that I couldn't get around.

Any way to do this? Thanks!

3 Answers
3

You have to first save stdout (by linking it on fd #4 for instance)

exec 4<&1

Redirect stdout

exec 1>bar

And restore saved stdout

exec 1<&4

dup2

exec 4<&-

There are likely several ways to do what you want, but probably the easiest would be a subshell or command group:

( some
commands
you
want
to
redirect ) >> logfile


The ( ... ) construct is a subshell; using { ... } is slightly lighter weight as it's just a group of commands. Which to prefer would depend on whether you want variables assigned inside the group to persist afterwards, primarily, although there are a couple other differences as well...

( ... )

{ ... }

{ block; }

The simplest way is:

{
echo "ALL THE THINGS"
} > OUTFILE


function verbose() {
local tmp stdout;
exec {stdout}>&1 {tmp}>>OUTFILE # Save STDOUT; append to OUTFILE
exec >&$tmp {tmp}>&- # dup tmp to STDOUT; close tmp
echo "ALL THE THINGS"
exec >&$stdout- # Restore STDOUT, close placeholder
}


Above, the echo will also go into OUTFILE.

echo

OUTFILE

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.