Text Processing – Deleting Lines Containing a Specified String in Different Files

Use the sed delete command (here assuming GNU sed as found on Ubuntu and other GNU systems).

 sed -i '/^[@#]/ d' sample.txt

If you need to account for leading space characters:

sed -i '/^\s*[@#]/ d' sample.txt

Assuming you have decent coding conventions, just delete any line greater than a certain size:

shopt -s extglob nullglob
sed -i.bak -r '/.{10000}/d' **/*.php

for @wildcard:

find . -name '*.php' -print0 | while IFS= read -rd "" file; do
    before=$(wc -l < "$file")
    after=$(sed -r '/.{10000}/d' "$file" | wc -l)
    case $(( diff = before - after )) in
        0) :;;  # no-op
        *) echo "will remove $diff lines from $file";;
    esac
done