Using Textwrangler as desktop search app
I would recommend using the 'twfind' command-line tool:
twfind specified-word /path/to/desired/file.txt
and as a live example:
twfind php /etc/apache2/httpd.conf
By default, TextWrangler will return matches to STDOUT but if you prefer that results be displayed within the app, you can include the '—gui' flag, e.g.
twfind php —gui /etc/apache2/httpd.conf
and for details on all the other options available, please see 'man twfind'.