In addition to what Bart said I'll point out that it's usually easier and
safer to avoid the eval by using an if/else block. Getting the quoting
right when using eval can be very difficult. Especially if you don't have
direct control over the text being eval'd; e.g., if some of it is supplied
by the user; or even just built up from earlier parts of the function.
I have several functions where 99% of the time I want the output
automatically piped into my pager (e.g., /usr/bin/less). But if the output
of the function is redirected away from my tty I don't want the pager in
the pipeline. So instead of using a variable that would normally contain "|
$PAGER" and sometimes be empty (i.e., using Ray's approach) I simply spell
it out:
if [[ -t 1 ]] ; then
grep -h -E $case_insensitive -- "$search_for" $files | $PAGER
else
grep -h -E $case_insensitive -- "$search_for" $files
fi