Comments on: shell scripting

By: antipaucity

antipaucity — Sat, 17 Oct 2009 07:46:05 +0000

Fair enough – rarely if ever see the $() construct in the environments I’ve been exposed-to: but good to know about

By: Alexei

Alexei — Fri, 16 Oct 2009 15:28:24 +0000

Legibility. I work with UNIX for about 15 yrs now, shell-scripting probably the same. I *know* the ticks well enough. But every now and then, I still get caught in a messy sequence of ‘ and ” and `, mostly when they’re nested.

Thus, replacing the backtick with $( ) makes things one degree less messy.

IMHO, naturally

By: antipaucity

antipaucity — Fri, 16 Oct 2009 03:51:38 +0000

Thanks, @Alexei – I do typically do a usage of some kind, and of course checking your input is *always* a good idea =D

Curious, though – why is the $() preferable to “ for grabbing the output of an exec’d command into the variable?

By: Alexei

Alexei — Fri, 16 Oct 2009 01:52:04 +0000

Also, you might want to turn the usage message into a function. I do that all the time:

———- cut here ———–
usage() {
echo “usage: ${0##*/} [on|off]” >&2
exit 1
}

# and then, some parameter checking
[[ -z "$1" || -z "$2" ]] && usage
[[ "$2" == "on" || "$2" == "off" ]] || usage
———- cut here ———–

By: Alexei

Alexei — Fri, 16 Oct 2009 01:10:16 +0000

Warren,

just a style/good-practice recommendation:

Instead of:
SERVICES=`chkconfig –list | cut -f 1 | grep -v ^$ | grep -v ‘:’ | sort`

Use:
SERVICES=$(chkconfig –list | cut -f 1 | grep -v ^$ | grep -v ‘:’ | sort)

It’s easier to read than the ticks.