🚏💃👗 mulle-strip-whitespace strips off leading and trailing spaces

mulle-strip-whitespace

#! /bin/sh
#
#   Copyright (c) 2021 Nat! - Mulle kybernetiK
#   All rights reserved.
#
#   Redistribution and use in source and binary forms, with or without
#   modification, are permitted provided that the following conditions are met:
#
#   Redistributions of source code must retain the above copyright notice, this
#   list of conditions and the following disclaimer.
#
#   Redistributions in binary form must reproduce the above copyright notice,
#   this list of conditions and the following disclaimer in the documentation
#   and/or other materials provided with the distribution.
#
#   Neither the name of Mulle kybernetiK nor the names of its contributors
#   may be used to endorse or promote products derived from this software
#   without specific prior written permission.
#
#   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
#   AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
#   IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
#   ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
#   LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
#   CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
#   SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
#   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
#   CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
#   ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
#   POSSIBILITY OF SUCH DAMAGE.
#
[ "${TRACE}" = 'YES' ] && set -x && : "$0" "$@"



####
#
# Prelude to be placed at top of each script. Rerun this script either in
# bash or zsh, if not already running in either (which can happen!)
# Allows script to run on systems that either have bash (linux) or
# zsh (macOS) only by default.

if [ "$1" != --no-auto-shell ]
then
   if [ -z "${BASH_VERSION}" -a -z "${ZSH_VERSION}" ]
   then
      exe_shell="`command -v "bash" `"
      exe_shell="${exe_shell:-`command -v "zsh" `}"

      script="$0"

      #
      # Quote incoming arguments for shell expansion
      #
      args=""
      for arg in "$@"
      do
         # True bourne sh doesn't know ${a//b/c} and <<<
         case "${arg}" in
            *\'*)
               # Use cat instead of echo to avoid possible echo -n
               # problems. Escape single quotes in string.
               arg="`cat <<EOF | sed -e s/\'/\'\\\"\'\\\"\'/g
${arg}
EOF
`"
            ;;
         esac
         if [ -z "${args}" ]
         then
            args="'${arg}'"
         else
            args="${args} '${arg}'"
         fi
      done

      #
      # bash/zsh will use arg after -c <arg> as $0, convenient!
      #

      exec "${exe_shell:-bash}" -c ". ${script} --no-auto-shell ${args}" "${script}"
   fi
   if [ ! -z "${BASH_VERSION}" ]
   then
      set +o posix
   fi
else
   shift    # get rid of --no-auto-shell
fi



# https://stackoverflow.com/questions/369758/how-to-trim-whitespace-from-a-bash-variable
r_trim_whitespace()
{
   RVAL="$*"
   RVAL="${RVAL#"${RVAL%%[![:space:]]*}"}"
   RVAL="${RVAL%"${RVAL##*[![:space:]]}"}"
}

#
# This script merely strips off leading and trailing spaces from
# the input. It may add an additional linefeed at the end if the input has
# none.
#
text="`cat "$@"`"

IFS=$'\n'
while read -r line
do
   r_trim_whitespace "${line}"
   printf "%s\n" "${RVAL}"
done <<< "${text}"