nixCraft

raj · #1 (**permalink**) 04-07-2009, 12:53 PM

if I add postfix_enable:="YES" in /etc/rc.conf postfix service starts on boot. However, if I don't it will not start on boot. This is easy to understand, but /usr/local/etc/rc.d/postfix startup script has small parameter expansion

Code:

: ${postfix_enable:="NO"}

How does it works? How this small code tells script whether postfix_enable set to YES or not in /etc/rc.conf file? Why : used before ${postfix_enable:="NO"}? Here is sample script:

Code:

. /etc/rc.subr

name="postfix"
rcvar=${name}_enable

load_rc_config $name

: ${postfix_enable:="NO"}
: ${postfix_pidfile:="/var/spool/postfix/pid/master.pid"}
: ${postfix_procname:="/usr/local/libexec/postfix/master"}
: ${postfix_flags:=""}

start_cmd=${name}_start
stop_cmd=${name}_stop
extra_commands="reload"

pidfile=${postfix_pidfile}
procname=${postfix_procname}

postfix_start() {
        /usr/local/sbin/postfix ${postfix_flags} start
}

postfix_stop() {
        /usr/local/sbin/postfix ${postfix_flags} stop
}

run_rc_command "$1"

nixcraft · #2 (**permalink**) 05-07-2009, 07:38 PM

If postfix_enable is defined AND NOT EMPTY, use postfix_enable value; otherwise, use "NO". Try it the following at terminal:

Code:

vech="BUS"
echo $vech
echo ${vech:="CAR"}
vech=""
echo ${vech:="CAR"}

if vech is not defined set its default value to CAR. line # 4 makes vech empty, thus default value set to car. This is known as parameter expansion. See bash man page for other fancy usage.

Code:

man bash

raj · #3 (**permalink**) 08-07-2009, 10:52 AM

Thanks!

Um..I'm not able to edit my post and add [Solved] prefix.

nixcraft · #4 (**permalink**) 08-07-2009, 11:11 AM

Quote:

Originally Posted by raj

Um..I'm not able to edit my post and add [Solved] prefix.

Must be permission issue. I will look into it ASAP.

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Config Parameter Expansion - How does it works?

Config Parameter Expansion - How does it works?

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raj (08-07-2009)