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Old 06-10-2007, 08:01 AM   #1
dziadgba
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Registered: Jun 2007
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converting string in integer in bash script


hello everybody,
I tried the following bash script

Code:
 #get number of lines of file nodesAndCoordinates
  lines= wc -l nodesAndCoordinates | gawk  '{print   $1}'

  echo $lines

  echo "done"
  lines=`expr $lines + 1`
  echo $lines
OUTPUT
- 23
-
-done
-1

why does it not give the right value (24)
I suppose that the number 23 is somehow stored in the variable lines as string and not as number. Can that be true? How can I convert variable lines in a number?

any help is appreciated
dzia

Last edited by dziadgba; 06-11-2007 at 06:33 AM.
 
Old 06-10-2007, 08:25 AM   #2
druuna
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Hi,

the lines= wc -l....... part isn't syntactically correct, it should be:

lines="`wc -l nodesAndCoordinates | gawk '{print 23}'`"

Besides that, the above line is strange. The output of the wc -l part is discarded (it is given to gawk, but gawk only prints 23) and 23 is printed. I don't know if the output of the wc -l line is actually needed, if not do something like this: lines="23".

Hope this helps.
 
Old 06-11-2007, 06:35 AM   #3
dziadgba
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I am sorry: the correct code is

lines= wc -l nodesAndCoordinates | gawk '{print $1}'

and the output would be 23.
The problem however remains the same.
thanks
 
Old 06-11-2007, 06:50 AM   #4
druuna
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Hi,

You are still using the wrong syntax:

It should be: lines=`wc -l nodesAndCoordinates | gawk '{print $1}'`
There should be backticks (`) around the statement.

I always surround a declaration with double quotes. I.e:

lines="`wc -l nodesAndCoordinates | gawk '{print $1}'`"
 
Old 08-31-2009, 05:25 PM   #5
tlinux17
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for increase a numeric variable, you can use this sintax
lines=$(($lines + 1))
Ciao
 
Old 08-31-2009, 05:59 PM   #6
chrism01
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Actually, you don't require the '$' inside the parentheses, in fact you can even do

(( a++ )) # Post-increment 'a', C-style.

http://www.tldp.org/LDP/abs/html/dblparens.html
 
  


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