The output message "Permission denied" comes from STDERR not from STDIN. You should redirect stderr to stdin on your command, to make it work. ifconfig wlan0 down 2>&1 | grep -i denied On Sun, Oct 25, 2009 at 2:42 PM, Eugeneapolinary Ju < eugeneapolinary81 at yahoo.com> wrote: > I just wrote a little script, that will echo a message to the user, if it > doesn't have enough permission: > > $ if ! [ "$(env LC_MESSAGES=C ifconfig wlan0 down | grep -i denied)" == "" > ]; then echo "no permission"; fi > SIOCSIFFLAGS: Permission denied > $ sudo su > [sudo] password for USER: > # if ! [ "$(env LC_MESSAGES=C ifconfig wlan0 down | grep -i denied)" == "" > ]; then echo "no permission"; fi > # > > but it won't works > > why? > > > _______________________________________________ > CentOS mailing list > CentOS at centos.org > http://lists.centos.org/mailman/listinfo/centos > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.centos.org/pipermail/centos/attachments/20091025/36209888/attachment-0004.html>