awk - Exclude or Include Records from a fixed-width file

The below command gets the records that have a value "new" in the given position (in this case the file was fixed-width). All other records which do not have the value "new" are ignored.

 awk '{if (substr($0, 7, 3) == "new") print $0}' file1.txt

substr 7, 3 is the starting position 7 with 3 characters

sed - Add a line to all files

#below inserts a line at 1st row with the content "Added new line using sed " in all the files in the path

for i in *; do sed -i '1s/^/Added new line using sed \n/' $i; done

#below inserts a line at 3rd row with the content "Added new line using sed " in all the files in the path

for i in *; do sed -i '3s/^/Added new line using sed \n/' $i; done