Lirt

# Exit on error
set -e
# Exit if variable was not set
set -u
# Exit when command in pipe fails
set -o pipefail
# Print every command executed with variable interpolation
set -x

Lirt

#  Print lines from line which match pattern to end of file
pattern=""
sed -n "/$pattern/,$ p" file.txt

# Example
pattern="mnop"
str="$(echo -e "abcd\nefgh\nijkl\nmnop\nqrst\nuvw\nxyz" | sed -n "/$pattern/,$ p")"
echo $str

# Remove lines before line LINE including LINE