File: setsub.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 # setsub [options...] [files...]
  27 #
  28 # SET SUBtraction emits only the lines from the first file given which don't
  29 # appear in later ones, never emitting the same line more than once.
  30 #
  31 # The options are, available both in single and double-dash versions
  32 #
  33 #   -h, -help    show this help message
  34 
  35 
  36 case "$1" in
  37     -h|--h|-help|--help)
  38         awk '/^# +setsub /, /^$/ { gsub(/^# ?/, ""); print }' "$0"
  39         exit 0
  40     ;;
  41 
  42     -) ;;
  43 
  44     --) shift ;;
  45 
  46     -*)
  47         printf "%s: unsupported option %s\n" "$0" "$1" >&2
  48         exit 1
  49     ;;
  50 esac
  51 
  52 # show all non-existing files given
  53 failed=0
  54 for arg in "$@"; do
  55     [ "${arg}" = "-" ] && continue
  56     [ -e "${arg}" ] && continue
  57     printf "%s: no file named \"%s\"\n" "$0" "${arg}" >&2
  58     failed=1
  59 done
  60 
  61 [ "${failed}" -gt 0 ] && exit 2
  62 
  63 awk '
  64     BEGIN {
  65         empty = 0
  66         for (i = 1; i < ARGC; i++) files[ARGV[i]]++
  67         for (k in files) if (files[k] > 1) { empty = 1; break }
  68     }
  69 
  70     FNR == 1 { first_input = FILENAME == ARGV[1] }
  71 
  72     {
  73         if (empty) next
  74         if (!first_input) {
  75             avoid[$0]++
  76             next
  77         }
  78         if (!tally[$0]++) lines[++n] = $0
  79     }
  80 
  81     END {
  82         for (i = 1; i <= n; i++) {
  83             l = lines[i]
  84             if (avoid[l]) continue
  85             print l
  86         }
  87     }
  88 ' "$@"