CentOS - Feb 2009 - Redirection in shell (was: squid HA failover?)

Hi,

Regarding the last example creating the config files with several
echos with redirection:

On Fri, Feb 6, 2009 at 20:37, J Potter <jpotter-centos at codepuppy.com>
wrote:
>        echo "node a.example.com" > /etc/ha.d/ha.cf
>        echo "node b.example.com" >> /etc/ha.d/ha.cf
>        echo "udpport 9000" >> /etc/ha.d/ha.cf
>        echo "bcast bond0" >> /etc/ha.d/ha.cf
>        echo "auto_failback off" >> /etc/ha.d/ha.cf
>        echo "logfile /var/log/ha-log" >> /etc/ha.d/ha.cf
>        echo "logfacility     local0" >> /etc/ha.d/ha.cf
I've seen this done too many times, and although this is the most
"popular" way of doing it in shell script, it is certainly not the
cleanest or the best. For one thing, it is inefficient in that it is
opening the file for every command line. And the code is not easy to
maintain, as if you change the filename you will have to change line
by line.

A better way to accomplish the same is:

{      echo "node a.example.com"
       echo "node b.example.com"
       echo "udpport 9000"
       echo "bcast bond0"
       echo "auto_failback off"
       echo "logfile /var/log/ha-log"
       echo "logfacility local0"
} >/etc/ha.d/ha.cf

And another way, using "here" documents is:

cat <<EDQ >/etc/ha.d/ha.cf
node a.example.com
node b.example.com
udpport 9000
bcast bond0
auto_failback off
logfile /var/log/ha-log
logfacility local0
EDQ

This second one is not so clean in that it "embeds" the document
inside the script, but it might be appropriate in some cases.

HTH,
Filipe