sed/TLDR (707 bytes)
1 Careful to not use GNU "extensions" in your POSIX sed: 2 3 no -i 4 no ; (use a newline) 5 6 Plan9 sed has: 7 sed [ -gln ] [ -e script ] [ -f scriptfile ] [ file ... ] 8 9 (range spec)command {args} 10 ! opposite range spec 11 12 a\ text on next line 13 text 14 15 i\ text on previous line 16 txt 17 18 c\ replace the line with text (ie. s/^.*$/text/) 19 text 20 21 N join next line 22 23 dD delete pattern space, DELETE FIRST LINE IN PATTERN SPACE 24 25 hH pattern space->hold space, APPENDING 26 gG hold space->pattern space, APPENDING 27 x hold space "exchange" pattern space 28 29 pnP print, print and next, PRINT FIRST LINE 30 31 = print line number 32 {} group commands 33 34 r {file} read file into output 35 w {file} write (appending) to file 36 tb: label jumps 37 38 q quit