I was able to do what i wanted by the following script
ls -ltr *.vmem |tr -s " " ";" |cut -d";" -f9 |sort -n > list_vmem
var1=`tr -s '\n' ' ' < list_vmem`
var2=`tr -s '\n' ',' < list_vmem`
echo $var2 > output_vmem.csv
paste -d"," $var1 >> output_vmem.csv
ls -ltr *.mem |tr -s " " ";" |cut -d";" -f9 |sort -n > list_mem
var1=`tr -s '\n' ' ' < list_mem`
var2=`tr -s '\n' ',' < list_mem`
echo $var2 > output_mem.csv
paste -d"," $var1 >> output_mem.csv
ls -ltr *.cpu |tr -s " " ";" |cut -d";" -f9 |sort -n > list_cpu
var1=`tr -s '\n' ' ' < list_cpu`
var2=`tr -s '\n' ',' < list_cpu`
echo $var2 > output_cpu.csv
paste -d"," $var1 >> output_cpu.csv



But can soembody PLs suggest one line solution for multiple files to be paste coulmn wise when we dont know the number of files to be pasted......

Thanks