move-if-change

#!/bin/sh
# Like mv $1 $2, but if the files are the same, just delete $1.
# Status is zero if successful, nonzero otherwise.

VERSION='2024-07-04 10:56'; # UTC
# The definition above must lie within the first 8 lines in order
# for the Emacs time-stamp write hook (at end) to update it.
# If you change this file with Emacs, please let the write hook
# do its job.  Otherwise, update this string manually.

# Copyright (C) 2002-2025 Free Software Foundation, Inc.

# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.

# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.

# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

usage="usage: $0 SOURCE DEST"

help="$usage
  or:  $0 OPTION
If SOURCE is different than DEST, then move it to DEST; else remove SOURCE.

  --help     display this help and exit
  --version  output version information and exit

The variable CMPPROG can be used to specify an alternative to 'cmp'.

Report bugs to <bug-gnulib@gnu.org>."

year=`expr "$VERSION" : '\([^-]*\)'`
version=`expr "$VERSION" : '\([^ ]*\)'`
version="move-if-change (gnulib) $version
Copyright $year Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law."

cmpprog=${CMPPROG-cmp}

for arg
do
  case $arg in
    --help | --hel | --he | --h)
      exec echo "$help" ;;
    --version | --versio | --versi | --vers | --ver | --ve | --v)
      exec echo "$version" ;;
    --)
      shift
      break ;;
    -*)
      echo "$0: invalid option: $arg" >&2
      exit 1 ;;
    *)
      break ;;
  esac
done

test $# -eq 2 || { echo "$0: $usage" >&2; exit 1; }

if test -r "$2" && $cmpprog -- "$1" "$2" >/dev/null; then
  rm -f -- "$1"
else
  if mv -f -- "$1" "$2"; then :; else
    # Ignore failure due to a concurrent move-if-change.
    test -r "$2" && $cmpprog -- "$1" "$2" >/dev/null && rm -f -- "$1"
  fi
fi

## Local Variables:
## eval: (add-hook 'before-save-hook 'time-stamp nil t)
## time-stamp-start: "VERSION='"
## time-stamp-format: "%:y-%02m-%02d %02H:%02M"
## time-stamp-time-zone: "UTC0"
## time-stamp-end: "'; # UTC"
## End: