[SOLVED] shell programming help: while loop

jestinjoy · 06-28-2010, 02:14 AM

Hi,

I am trying to do some shell programs. I tried some sites for help. Regarding the while loop, they give the structure as

Code:

while [ n1 -lt 500 ]
do
	echo $((n1+100))
done

But the below code also worked for me

Code:

while ((n1 > 500))
do
	echo $((n1+100))
done

By using (( )) i could use while, for... But the documentations didnt follow this way. Please help me on this. Any problem using this way. I mainly use this for datastructure programming.

timmeke · 06-28-2010, 02:29 AM

For arithmetic comparison, as in your case, (( )) is fine. See man bash, sections on arithmetic evaluation and conditional expressions.

Do note that n1 -lt 500 is equivalent to n1 < 500, not n1 > 500 (-lt is short for "less than").

jestinjoy · 06-28-2010, 02:32 AM

thanks for the info.

vikas027 · 06-28-2010, 02:55 AM

You can also use the below code as per your requirement.

Code:

-sh-3.00$ awk '
BEGIN {
x=1;
while(1)
{           
print "Iteration"
if ( x==5 )
break;
x++;
}
}
'
Iteration
Iteration
Iteration
Iteration
Iteration

OR

Code:

awk 'BEGIN{while(i++ < 5)print "Iteration\t"}'

pr_deltoid · 06-28-2010, 03:11 AM

http://tldp.org/LDP/abs/html/index.html is good.