File: tacl.sh
   1 #!/bin/sh
   2 
   3 # The MIT License (MIT)
   4 #
   5 # Copyright (c) 2026 pacman64
   6 #
   7 # Permission is hereby granted, free of charge, to any person obtaining a copy
   8 # of this software and associated documentation files (the "Software"), to deal
   9 # in the Software without restriction, including without limitation the rights
  10 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  11 # copies of the Software, and to permit persons to whom the Software is
  12 # furnished to do so, subject to the following conditions:
  13 #
  14 # The above copyright notice and this permission notice shall be included in
  15 # all copies or substantial portions of the Software.
  16 #
  17 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  18 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19 # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  20 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  21 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  22 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  23 # SOFTWARE.
  24 
  25 
  26 # tacl [options...] [files...]
  27 #
  28 # Like `tac`, TAC Lines emits lines in reverse order (last to first).
  29 # Unlike `tac`, TAC Lines ensures no lines across inputs are accidentally
  30 # joined, since all lines it outputs end with line-feeds, even when the
  31 # original files don't.
  32 #
  33 # The options are, available both in single and double-dash versions
  34 #
  35 #   -h, -help    show this help message
  36 #   -0, -null    turn null-byte-delimited chunks into proper lines
  37 
  38 
  39 nulled=0
  40 
  41 while [ $# -gt 0 ]; do
  42     case "$1" in
  43         -h|--h|-help|--help)
  44             awk '/^# +tacl /, /^$/ { gsub(/^# ?/, ""); print }' "$0"
  45             exit 0
  46         ;;
  47 
  48         -0|--0|-null|--null) nulled=1; shift; continue ;;
  49 
  50         -) break ;;
  51 
  52         --) shift; break ;;
  53 
  54         -*)
  55             printf "%s: unsupported option '%s'\n" "$0" "$1" >&2
  56             exit 1
  57         ;;
  58     esac
  59 
  60     break
  61 done
  62 
  63 # show all non-existing files given
  64 dashes=0
  65 failed=0
  66 for arg in "$@"; do
  67     if [ "${arg}" = "-" ]; then
  68         dashes="$((dashes + 1))"
  69         continue
  70     fi
  71     [ -e "${arg}" ] && continue
  72     printf "%s: no file named \"%s\"\n" "$0" "${arg}" >&2
  73     failed=1
  74 done
  75 
  76 if [ "${dashes}" -gt 1 ]; then
  77     printf "%s: can't read from the standard input more than once\n" "$0" >&2
  78     failed=1
  79 fi
  80 
  81 [ "${failed}" -gt 0 ] && exit 2
  82 
  83 src='
  84     BEGIN { if (nulled) RS = "\000" }
  85     FNR == 1 { gsub(/^\xef\xbb\xbf/, "") }
  86     {  gsub(/ *\r?$/, ""); lines[NR] = $0 }
  87     END { for (i = NR; i >= 1; i--) print lines[i] }
  88 '
  89 
  90 awk -v nulled="${nulled}" "${src}" "$@"