conditional redirection in bash

For bash, you can use the line:

exec &>/dev/null

This will direct all stdout and stderr to /dev/null from that point on. It uses the non-argument version of exec.

Normally, something like exec xyzzy would replace the program in the current process with a new program but you can use this non-argument version to simply modify redirections while keeping the current program.

So, in your specific case, you could use something like:

tty -sif [[ $? -eq 1 ]] ; then    exec &>/dev/nullfi

If you want the majority of output to be discarded but still want to output some stuff, you can create a new file handle to do that. Something like:

tty -sif [[ $? -eq 1 ]] ; then  exec 3>&1 &>/dev/nullelse   exec 3>&1fiecho Normal               # won't see this.echo Failure >&3          # will see this.

I found another solution, but I feel it is clumsy, compared to paxdiablo's answer:

if tty -s; then   REDIRECT=/dev/ttyelse   REDIRECT=/dev/nullfiecho "Normal output" &> $REDIRECT

You can use a function:

function the_code {    echo "is this visible?"    # as many code lines as you want}if tty -s; then # or other condition  the_codeelse   the_code >& /dev/nullfi