Shell Programming and Scripting

cat *.txt | while read file
do
grep 3500[1-6] file | tr '\012' ','
done

$ cat test_file
one.txt 35001,35002,35005,35006
two.txt 35002,35003,35004,35005,35006
three.txt 35001,35002, 35003,35004,35005,35006
four.txt 35001,35006

$  awk -F'[ ,]' '{printf $1 " ";for(i=$2;i<=$NF;i++)printf ($0~i)?(i<$NF)? i OFS:i:OFS;printf RS}' OFS="," test_file

one.txt 35001,35002,,,35005,35006
two.txt 35002,35003,35004,35005,35006
three.txt 35001,35002,35003,35004,35005,35006
four.txt 35001,,,,,35006

awk -F"," '{for(i=$1;i<=$NF;i++) {++j;if ( $j != i) { printf FS ;--j } else { printf (j==NF)?i: i FS}} printf "\n";j=0}'  filename