Using Floating Numbers in String

tintin72 · #1 (**permalink**) 06-29-2009

Dear Unix Gurus,

I have a list of files that I want to loop over....for example:

Code:

 
sl40_z11.70.txt
sl41_z11.40.txt
sl42_z11.10.txt
sl43_z10.80.txt

using the script

Code:

 
#!/bin/sh
#
echo -n "....enter first Z-coordinate position....."; read zpos
q="scale=3; $zpos"
p=0.3
#
loopNumber=$[($lastslice - $firstslice)+1]
echo "loopNumber is $loopNumber"
echo firstslice no. is $firstslice
 
for ((i=$firstslice; i<=$loopNumber; i++)); do 
n=$[i]
for ((k=0; k<=$loopNumber; k++)); do 
r=$[k] ; f=$r*$p ; zposition=$q-$f 
 
echo "sl$[n]_z$[zposition].txt"
 
done
done

where firstslice is 40 and lastslice is 43 and 0.3 is the difference in z-cordinate btw the files.

My problem is that the script works fine with the exception that bash doesn't recognize $zposition. It apparently can't handle iteration with floating numbers? Can someone help?

Cheers

jayan_jay · #2 (**permalink**) 06-29-2009

Try this and change according to ur variables.

echo "scale=4;$b+$c" | bc

tintin72 · #3 (**permalink**) 06-29-2009

Quote:

Originally Posted by jayan_jay

Try this and change according to ur variables.

echo "scale=4;$b+$c" | bc

I'm not sure I understand you. Doing

Code:

echo "$zposition" |bc

returns the correct output. But doing

Code:

echo "sl$[n]_z$[zposition].txt"

does not. This is my problem.

jayan_jay · #4 (**permalink**) 06-29-2009

Try this
echo "sl${n}_z${zposition}.txt"

tintin72 · #5 (**permalink**) 07-01-2009

Quote:

Originally Posted by jayan_jay

Try this
echo "sl${n}_z${zposition}.txt"

doesn't work. can I just ask..did you actually try out your suggestions bufore suggesting them to the forum?

fpmurphy · #6 (**permalink**) 07-01-2009

Humm, I have looked at this shell script a few times and scratched my head.

You set the variable 'q' to a string

Code:

q="scale=3; $zpos"

yet you expect to be able to subtract a number from it

Code:

zposition=$q-$f

How is this meant to work?

tintin72 · #7 (**permalink**) 07-06-2009

Quote:

Originally Posted by fpmurphy

Humm, I have looked at this shell script a few times and scratched my head.

You set the variable 'q' to a string

Code:

q="scale=3; $zpos"

yet you expect to be able to subtract a number from it

Code:

zposition=$q-$f

How is this meant to work?

Hi,

I revisited it too and scratched my head as well! There's a bug in the script...if firstslice is bigger than lastslice it won't work. So I've tried a different tack using awk.

as a reminder, this is what I want to do; I have a list of files:

Code:

 
sl40_z11.70.txt
sl41_z11.40.txt
sl42_z11.10.txt
sl43_z10.80.txt

I want to loop through these files keeping their labelling intact. For example, I want to do in a single script

Code:

cp sl40_z11.70.txt sl40_z11.70.dat
cp sl41_z11.40.txt sl41_z11.40.dat
cp sl42_z11.10.txt sl42_z11.10.dat
cp sl43_z10.80.txt sl43_z10.80.dat

I have hundreds of these files and I need to carry out other non-trivial operations on them. Problem is bash does not recognize floating numbers so I can't loop over them.

my new script is :

Code:

 
#!/bin/sh
#
echo -n "....enter first slice number....."; read firstslice
echo -n "....enter last slice number....."; read lastslice
#
echo -n "....enter first Z-coordinate position....."; read zpos
#sliceDiff=0.3
#
loopNumber=$[($lastslice - $firstslice)+1]
echo "loopNumber is $loopNumber"
echo firstslice no. is $firstslice
for ((k=$firstslice;k<=$lastslice; k++)); do 
r=$[k]
echo "$firstslice $r $zpos" | awk '{print $3-(($2-$1)*0.3)}'
#echo "$firstslice $r $zpos" | awk '{print $i}' sl$2_z[$3-(($2-$1)*0.3)].txt > xxxx.dat
done

So running this script and entering at prompts "40" , "43", "11.70"
loops over the 4 files nicely. But I don't know how to incorporate the output into the last line of the script so that awk recognizes the filename.

Any help would be much appreciated.

Cheers

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