script in korn shell

disruptive · 02-07-2007, 10:06 AM

Hi

I very neatly would like to split my input lines into two variables. Each bit of data is divided by a space. My code is below, how can I do this?

Thanks

#!/bin/ksh
i = 0
while read line_by_line
do

let "i=i+1"
echo $i
echo ${line_by_line}
done < myfile.txt

Input file

0 10
10 3
20 67
30 89

stress_junkie · 02-07-2007, 10:20 AM

Add a second variable in the read statement. The first lexical object will go into the first variable while the rest of the line will go into the second variable.

Code:

...
while read first second
do

let "i=i+1"
echo $i
echo $first $second
done < myfile.txt

You can test it by printing a constant in between $first and $second.

Code:

...
echo $first then $second
...

disruptive · 02-07-2007, 11:02 AM

OK how do I do an if then. Its not working I am not sure whether I need to use the expr statement?
Can somebody show me the correct statement for two number being less than or equal to.

Thanks

jim mcnamara · 02-07-2007, 11:07 AM

Code:

while read line
do
    read var1 var2
    if [[ "$var1" != "$var2" ]] ; then
       echo "$var1 does not equal $var2"
    fi
done < inputfile

disruptive · 02-07-2007, 11:11 AM

More questions.

How can I perform non integer additions and arithmetic?

schneidz · 02-07-2007, 11:33 AM

i would create a c-program and call it in the script with the appropriate arguements.

awk may be able to do float math but im not sure of syntax.

disruptive · 02-07-2007, 11:39 AM

what about bc is that a way?

stress_junkie · 02-07-2007, 04:40 PM

Quote:

Originally Posted by disruptive

what about bc is that a way?

Why don't you just try it and find out? A little self reliance goes a long way.

You could have found out about the read command using multiple variables just by reading the man page. You could find out about using bc in a script by trying it.

You're not going to get very far if you refuse to do the simplest things to help yourself.

jim mcnamara · 02-07-2007, 08:18 PM

Yes. You can use bc.

ksh lets you force an arithmetic evaluation with the (( )) construct -
eg (( 3 + 1 )).... Try it with float values and see if it works or not...

matthewg42 · 02-07-2007, 08:33 PM

for non-integer arithmetic, you can also use zsh which supports it internally, as well as many other nice features.

If you're going to do a lot more sophisticated stuff, I'd consider moving to a more complete language. Perl or Python are both nice, and both have huge libraries of pre-written modules for doing a great deal of stuff. They also both have quite nice mechanisms for you to put your own code in mudules and allow easy re-use/sharing.

C is a lot harder to do well because yuo have to manage your own memory. Of course it has it's moments. There isn't really anything which can touch C for OS coding. (/me dons aspestos underpants).

disruptive · 02-19-2007, 08:36 AM

Thanks for the tip-off about zsh,

I am trying the same thing, however I am noting that when I am reading in values from a file, they are not being added as floating point values but instead appear truncated. I have looked but to no avail. Can you suggest where the program is failing.

#!/bin/zsh
let "i = 0"
let "sum = 0"
echo "Min MC: "
read MinMC

#x=2.5
#y=3.456
#(( res = x / y ))

#echo $res
#(( res = x + y ))
#echo $res
#(( res = x * y ))
#echo $res

while read MC Value
do
#echo $MC $Value
if ((MinMC <= MC))
then

((i=i+1))
# echo $i
let "sum=sum+Value"
#else
#echo nothing
fi
#echo ${Value}
done < myfile.txt
echo Sum: $sum
echo count: $i
((average = sum / i))
echo average: $average

cfaj · 02-20-2007, 11:17 PM

Quote:

Originally Posted by jim mcnamara

Yes. You can use bc.

ksh lets you force an arithmetic evaluation with the (( )) construct -
eg (( 3 + 1 )).... Try it with float values and see if it works or not...

ksh93 can do arithmetic with decimal fractions, but other versions, including pdksh, cannot.

bigearsbilly · 02-21-2007, 02:54 AM

you can only do integer arithmetic in korn.
use dc or perl or python

cfaj · 02-21-2007, 11:33 AM

Quote:

Originally Posted by bigearsbilly

you can only do integer arithmetic in korn.
use dc or perl or python

Korn Shell 93 can do decimal fractions:

Code:

$ echo $0
/usr/local/bin/ksh93
$ echo $(( 1.3 * 2.4 ))
3.12

matthewg42 · 02-21-2007, 12:01 PM

Quote:

Originally Posted by cfaj

Korn Shell 93 can do decimal fractions:

Code:

$ echo $0
/usr/local/bin/ksh93
$ echo $(( 1.3 * 2.4 ))
3.12

I was surprised to see this, so I checked...

Code:

matthew@chubby:~$ ksh
$ echo $(( 1.3 * 2.4 ))
3.1200000000000001
$ exit
matthew@chubby:~$ which ksh
/usr/bin/ksh
matthew@chubby:~$ ksh --version
zsh 4.3.2 (i686-pc-linux-gnu)
matthew@chubby:~$ ls -l `which ksh`
lrwxrwxrwx 1 root root 29 2007-02-06 17:16 /usr/bin/ksh -> /etc/alternatives/usr.bin.ksh

Aha, the old alternatives thing... OK, install actual ksh:

Code:

matthew@chubby:~$ sudo apt-get install ksh
Password:
...
matthew@chubby:~$ ksh --version
  version         sh (AT&T Labs Research) 1993-12-28 r
matthew@chubby:~$ ksh
$ echo $(( 1.3 * 2.4 ))
3.12

Wow - it works. Now for pdksh:

Code:

matthew@chubby:~$ pdksh
$ echo $(( 1.3 * 2.4 ))
pdksh:  1.3 * 2.4 : unexpected `.'

So there you have it. ksh93 - floating point works, but pdksh not.