As far as I know, 'match' function is part of POSIX spec for awk. Only the third array argument is specific to gawk. So, this should work for any awk. awk

As far as I know, 'match' function is part of POSIX spec for awk. Only the third array argument is specific to gawk. So, this should work for any awk. awk 'match($0, /^#+ /){l=RLENGTH-1; print "<h" l ">" substr($0,RLENGTH+1) "</h" l ">"}' I checked it on https://awk.js.org/ https://awk.js.org/ and it did work