UNIX for Dummies Questions & Answers

Both ((expression)) and $((expression)) perform an arithmetic evaluation of expression. After evaluating expression, $((expression)) returns a string representing the resulting value. ((expression)) returns a 0 exit status if expression evaluates to a non-zero value and 1 otherwise.

Other than the time taken to format the results, there shouldn't be any noticeable difference in speed between ((expression)) and $((expression)).

Note that the standards require conforming shells to support arithmetic expansion ($((expression))). The standards explicitly allow for the arithmetic evaluation command (((expression))) to be provided, but do not currently require conforming shells to provide it. The standards also explicitly require applications that invoke nested subshells to separate the opening parentheses opening the subshell environments with one or more IFS characters to avoid an ambiguity in the grammar in shells that support the arithmetic evaluation command.

I mean ((x+=1)) is much faster than (($x+=1))

And that is dependent on the code being in a loop. ksh precompiles loops and executes the compiled code. With the second form, ksh must expand the variable and then rescan the full resulting expression. With the first form ksh can use the compiled code with no rescan.

Hi Robin,
I have changed the syntax as you menitoned and i tried.
Now it is working fine.
if [ $i -gt 1 ];

Thank you so much for your help...

Thanks
Shiva