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Simply shell script question

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# 1  
Old 07-01-2005
Simply shell script question
Struggling to add numbers in shell script..


ie.
a=3
b=4

c=$a + $b

echo $c

I thought this should give me 7 - but cannot see what wrong.. should be simple answer eh?
# 2  
Old 07-01-2005
In ksh/bash

c=$((a + b))

In sh
c=`expr $a + $b`
# 3  
Old 07-01-2005
or in ksh/bash more simply:
(( c= a + b ))
# 4  
Old 07-01-2005
Won't it be better to use the 'expr' command everywhere, so that the script remains portable even to older systems or systems without ksh?
# 5  
Old 07-01-2005
thank guys - new it was simple - just has been a while...
# 6  
Old 07-01-2005
Quote:
Originally Posted by blowtorch
Won't it be better to use the 'expr' command everywhere, so that the script remains portable even to older systems or systems without ksh?
why not - just code everything in Bourne [#!/bin/sh] [if you really enjoy pain]
# 7  
Old 07-02-2005
i'm facing more difficult issue as follows:
file.txt contains:
1676
18060
10004
996
1836
16136
1712
176
10220
78908

i want todo something like
for i in `awk '{print $1}' file.txt` ; do sum="$(($i+$i))" ; done

what i really need todo with sum="$(($i+$i))" to make it add all the numbers to give me a final sum?
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