# If you'd like to omit non-matching lines from the result; add ';d' to the end of the expression.
sed -E 's/(nazwa.*rozmiar\n)([\s\w\n]*)([-]{26})/$2/gm;t' <<< "nazwa plik rozmiar
progra exe 3560k
obraz gif 500k
obraz1 gif 500k
obraz2 gif 1500k
obraz3 gif 2500k
obraz4 gif 3500k
tekst txt 20k
--------------------------"
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for SED, please visit: https://www.gnu.org/software/sed/manual/html_node/The-_0022s_0022-Command.html