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expr command

 
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# 1  
Old 03-05-2007
expr command
hi guys....


i hava a command expr... where i m adding a value in a loop
like
Tc=`expr $Tc\+ $l`
where
Tc is declred as a variable and every time l contains a new vaue
if
Tc =0 initially
and l =2
Tc should be equal to 0+ 2
and then
l = 4
Tc = 2+4

and dispaly as 6

but after on iteration it is not adding up the value...

any reason for it
# 2  
Old 03-05-2007
Quote:
Tc=`expr $Tc\+ $l`
why is the \+ ?

Could be just,
Tc=`expr $Tc+ $l`

Could you please post your script if possible ?
# 3  
Old 03-05-2007
It helps to post what answer you're getting as well. It might point to what the problem is.

Carl
# 4  
Old 03-05-2007
expr command
hi
this is the script

for i in `ls q*.txt`
do
l=0
tc=0
var=`tail -1 $i`
l=`echo $var | cut -d'|' -f2`
tc=`expr $tc+$l`
done

every time it gives the first answer
i.e if l =2
for the first time
it prints 2 always
if l = 6 next time
tc = 8 is expected
but displays 2 only
# 5  
Old 03-05-2007
Quote:
Originally Posted by madhu_aqua14
hi
this is the script

for i in `ls q*.txt`
do
l=0
tc=0
var=`tail -1 $i`
l=`echo $var | cut -d'|' -f2`
tc=`expr $tc+$l`
done

every time it gives the first answer
i.e if l =2
for the first time
it prints 2 always
if l = 6 next time
tc = 8 is expected
but displays 2 only
Code:
tc=0
for i in `ls q*.txt`
do
  l=`tail -1 $i | cut -d'|' -f2`
  tc=`expr $tc + $l`
  echo $tc
done

# 6  
Old 03-05-2007
Quote:
Originally Posted by madhu_aqua14
hi
this is the script
Code:
for i in `ls q*.txt`

Do not do that. Not only is ls unnecessary and slow, but it will break your script if there are any spaces or other pathological characters in any filenames.

Use:

Code:
for i in q*.txt

Quote:
Code:
do
l=0
tc=0
var=`tail -1 $i`
l=`echo $var | cut -d'|' -f2`
tc=`expr $tc+$l`
done

every time it gives the first answer
i.e if l =2
for the first time
it prints 2 always
if l = 6 next time
tc = 8 is expected
but displays 2 only
You reset $tc to 0 on every iteration of the loop. Set it before the loop.
Last edited by vgersh99; 03-07-2007 at 11:55 AM..
 
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