File: stomp.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 # stomp [filepaths...]
  27 #
  28 # Turn runs of empty lines into single empty lines, effectively squeezing
  29 # paragraphs vertically, so to speak; runs of empty lines both at the start
  30 # and at the end are completely ignored.
  31 #
  32 # This script also ensures no lines across inputs are accidentally joined,
  33 # since all lines it outputs end with line-feeds, even when the original
  34 # files don't.
  35 
  36 
  37 case "$1" in
  38     -h|--h|-help|--help)
  39         # show help message, using the info-comment from this very script
  40         awk '/^# +stomp /, /^$/ { gsub(/^# ?/, ""); print }' "$0"
  41         exit 0
  42     ;;
  43 esac
  44 
  45 [ "$1" = '--' ] && shift
  46 
  47 command='awk'
  48 if { [ -p /dev/stdout ] || [ -t 1 ]; } && [ -e /usr/bin/stdbuf ]; then
  49     command='stdbuf -oL awk'
  50 fi
  51 
  52 # show all non-existing files given
  53 failed=0
  54 for arg in "$@"; do
  55     if [ "${arg}" = "-" ]; then
  56         continue
  57     fi
  58     if [ ! -e "${arg}" ]; then
  59         printf "no file named \"%s\"\n" "${arg}" > /dev/stderr
  60         failed=1
  61     fi
  62 done
  63 
  64 if [ "${failed}" -gt 0 ]; then
  65     exit 2
  66 fi
  67 
  68 ${command} '
  69     /^\r?$/ { empty = 1; next }
  70     empty { empty = 0; if (n > 0) print "" }
  71     { n++; print }
  72 ' "$@"