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Old 06-28-2010, 03:14 AM   #1
jestinjoy
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Registered: May 2004
Location: India
Distribution: Ubuntu 9.04, Debian Lenny
Posts: 121

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Smile shell programming help: while loop


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.
 
Old 06-28-2010, 03:29 AM   #2
timmeke
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Registered: Nov 2005
Location: Belgium
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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").
 
Old 06-28-2010, 03:32 AM   #3
jestinjoy
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Registered: May 2004
Location: India
Distribution: Ubuntu 9.04, Debian Lenny
Posts: 121

Original Poster
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re

thanks for the info.
 
Old 06-28-2010, 03:55 AM   #4
vikas027
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Registered: May 2007
Location: Sydney
Distribution: RHEL, CentOS, Debian, OS X
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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"}'
 
Old 06-28-2010, 04:11 AM   #5
pr_deltoid
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Registered: Jun 2010
Distribution: Fedora
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http://tldp.org/LDP/abs/html/index.html is good.
 
  


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