[SOLVED] || && problem

Al Effendi · 11-09-2009, 04:00 PM

hi
thanks in advance

$ command1 || command2 || command3 || command4
I know This line of code will not run the next command in the sequence unless the prior command has returned "false" i.e. 1

BUT I cannot understand the foll.
(( 200 || 11 )) # Logical OR
echo $?
# answer 1

why?
what do 200, 11 represent ?

Or for that matter
if ( ( 1 && 2 ) || ! 3 ) then
echo TRUE
else
…

# answer TRUE

why?
what do 1,2,3 represent ?

appreciate help

kbp · 11-09-2009, 07:18 PM

Plenty of detail here:
http://www.faqs.org/docs/abs/HTML/tests.html
http://www.faqs.org/docs/abs/HTML/dblparens.html

..let us know if you still need assistance

cheers

Al Effendi · 11-10-2009, 12:22 AM

hi
thanks all
yes I still need assistance. I can understand if the above commands were like ls nosuchfile or dir nosuchfile but numbers ?

kbp · 11-10-2009, 01:20 AM

Do you have a script that uses one of these constructs ? .. they appear to be incorrectly used

thanks

timmeke · 11-10-2009, 02:54 AM

Going by http://www.faqs.org/docs/abs/HTML/dblparens.html, the code with numbers is interpreted as C code.
In C language, any non-zero number is regarded as logical true, zero being logical false.
So:

Code:

(( 200 || 11 )) == true OR true == true (result = 1)
(( 1 && 2 ) || ! 3 ) == ((true AND true) OR !true) == ( true OR false ) == true

Needless to say, the constructs are a bit strange, and even make me think of homework on boolean algebra...

I suggest you read up on the double paranthesis (( )) operator, which is used for C-style arithmetic operations.
Not to be confused with logical operators that link together commands, nor with bitwise logic.

Al Effendi · 11-11-2009, 02:28 PM

Al Effendi

pixellany · 11-11-2009, 04:12 PM

Al_Effendi;

I merged your last post into this thread----it appears you intended to answer here (but you started a new thread.)

Good luck