KSH if-then v. [[ ]] && || notation and relative speed of equivalent command constructs

[DaviD W. Sanderson]

In article <1991Apr15.165925.26321 at ux1.cso.uiuc.edu> jeffo at uiuc.edu writes:
>In KSH, which is faster:
>
>if [[ ${a} = 5 ]] then print 'a is set to 5'
>else print 'a is not set to 5'
>...or...
>[[ ${a} = 5 ]] && print 'a is set to 5' || print 'a is not set to 5'

I would guess these are about the same (I don't know for sure).
In this specific instance both are left in the dust by

	case $a
	{
	5)	print 'a is set to 5'
		;;
	*)	print 'a is not set to 5'
		;;
	}

A general rule is that it is fastest to use "case" when all you want to
do is pattern matching.  Note that the $a is implicitly quoted in the
case syntax, so it doesn't matter if it contains white space.  It is
superflous to use

	case "$a"

Other supposedly sh-compatible shells may not do this implicit quoting.
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      / __\  U N S H I N E	           DaviD W. Sanderson
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