Re: Korn Shell [[ ... ]] operator

[Derek Ragona]

The [[ ]] operators are for compound tests, the [ ] operator is for simple 
tests.  In ksh newer than 6/3/86 the [[ ]] makes the [ ] obsolete.



Example of [[ ]]:
[[ foo > bar && $PWD -ef . ]] && print foobar
foobar


That is from the kornshell book co-written by David Korn.

By the way, I use ksh for my root's shell and it works fine.

-Derek


At 10:31 AM 9/25/2006, Arindam wrote:

I know csh is the shell of choice on FreeBSD. But I have this question
on Korn Shell and it would be great if somebody could explain.

Can someone tell me a little more about the Korn Shell [[ ... ]]
double-brackets construct used for comparing string expressions. How
does it differe from the standard [ ... ] single brackets.

You could tell me to RTFM but I haven't gleaned enough clarity from
such efforts already expended.

It would be great if you could give some idea through examples.

Cheers,
Andy
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Re: Korn Shell [[ ... ]] operator

[Dan Nelson]

In the last episode (Sep 25), Arindam said:
> I know csh is the shell of choice on FreeBSD. But I have this question
> on Korn Shell and it would be great if somebody could explain.
> 
> Can someone tell me a little more about the Korn Shell [[ ... ]]
> double-brackets construct used for comparing string expressions. How
> does it differe from the standard [ ... ] single brackets.

Different comparison operators, basically, and faster than [ because it
doesn't have to fork /bin/[ .
 
> You could tell me to RTFM but I haven't gleaned enough clarity from
> such efforts already expended.

They're all documented in the manpage ("ksh93" for the shells/ksh93
ports), under Conditional Expressions.  Compare them with the "test"
manpage.  It looks like FreeBSD's test command does most of what ksh
does, except for the wildcard matching of =, which is handy but can be
emulated with a case statement :)

-- 
Dan Nelson
[EMAIL PROTECTED]
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