Exclude delimiter with csplit

Since you seem to be using gnu csplit, it's quite simple:

csplit --suppress-matched infile /PATTERN/ '{*}'

i.e. use --suppress-matched to suppress the lines matching PATTERN.

---

Per your note, this option is available only with more recent versions of csplit (coreutils ≥ 8.22)

perl -ne 'BEGIN { $fnum=0; open $fh, ">", sprintf "xx%02d", $fnum++ } if (m/-/) { open $fh, ">", sprintf "xx%02d", $fnum++ } else { print $fh $_ }' inputfileorfileshere

Or a similar reopen-into-new-file-on-matching-appropriate-line via awk or whatever.

If you can make do with a string match rather than a regex match

awk 'BEGIN {RS="---\n"; ORS=""} {print > sprintf("xx%02d", NR)}' in

With GNU awk (at least in v4.0.1) it is possible to use a regex for RS e.g.

gawk 'BEGIN {RS="-+\n"; ORS=""} {print > sprintf("xx%02d", NR)}' in