File: setint.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 # setint [options...] [file] [file]
  27 #
  28 # SET INTersection emits only the lines which are common to both the input
  29 # files given.
  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 "$1" in
  37     -h|--h|-help|--help)
  38         awk '/^# +setint /, /^$/ { 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 if [ $# -ne 2 ]; then
  62     printf "%s: given %d inputs instead of exactly 2\n" "$0" "$#" >&2
  63     failed=1
  64 fi
  65 
  66 [ "${failed}" -gt 0 ] && exit 2
  67 
  68 awk '
  69     BEGIN { all = ARGV[1] == ARGV[2] }
  70 
  71     FNR == 1 {
  72         first_input = FILENAME == ARGV[1]
  73         # if first input is empty, the resulting set-intersection is empty,
  74         # so just quit right away
  75         if (!first_input && !n) exit
  76     }
  77 
  78     {
  79         if (!tally[$0]++) lines[++n] = $0
  80         if (all) next
  81         if (first_input) { tally1[$0]++ } else { tally2[$0]++ }
  82     }
  83 
  84     END {
  85         for (i = 1; i <= n; i++) {
  86             l = lines[i]
  87             if (all || (tally1[l] > 0) && (tally2[l] > 0)) print l
  88         }
  89     }
  90 ' "$@"