Shell Programming and Scripting

awk '{fn=++b".dat";a=$0;getline;printf("%s\n%s\n",a,$0)> fn}' file

for i in {1999..2008} ; do 
    split -d -l 2100 $i.txt $i 
    for j in {11..0} ; do 
        mv ${i}${j} ${i}$((j+1)).txt
    done
done

mv: cannot stat `20074': No such file or directory
mv: cannot stat `20073': No such file or directory
mv: cannot stat `20072': No such file or directory
mv: cannot stat `20071': No such file or directory
mv: cannot stat `20070': No such file or directory

for i in {1999..2008} ; do
   split -d -l 2100 $i.txt $i 
   for j in {11..0} ; do 
       j0=`printf "%02d" $j`
       j1=`printf "%02d" $((j+1))` 
       mv ${i}${j0} ${i}${j1}.txt 
   done
done