Always include first line in grep

You could include an alternate pattern match for the one of the column names. If a column was called COL then this would work:

$ grep -E 'COL|pattern' file.csv

sed:

sed '1p;/pattern/!d' input.txt

awk:

awk 'NR==1 || /pattern/' input.txt

grep1:

grep1() { awk -v pattern="${1:?pattern is empty}" 'NR==1 || $0~pattern' "${2:-/dev/stdin}"; }