inplace

#! /bin/sh
##
## inplace - Script for 'in place' file replacing
## Copyright (c) 2006 by Michal Nazarewicz <mina86@mina86.com>
##
## 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 <http://www.gnu.org/licenses/>.
##
## This is part of Tiny Applications Collection
##   -> http://tinyapps.sourceforge.net/
##


set -e
readonly ARGV0=${0##*/}

err () {
	echo "$ARGV0: $*" >&2
	exit 1
}



##
## usage
##
usage () {
	echo 'inplace 0.1 (c) 2006 by Michal Nazarewicz (mina86/AT/mina86.com)'
	[ X"$1" != Xversion ] || exit 0

	cat <<EOF

usage: $ARGV0 -h | --help | -V | --version
       $ARGV0 [ -s[<suffix>] ] <command> [ <argumet> ... ] -- <file> [ ... ]

Runs <command> with given <argument>s for each <file> as a standard
input replacing it's contents with what <command> outputs to standard
output.

Options:
  -h --help     displays this help screen
  -V --version  displays version
  -s<suffix>    back ups each <file> to <file><suffix>
  -s            back ups each <file> to <file>.bak

When separating file names and command arguments the first '--' is used.
EOF

}


##
## Parse args
##
SUFFIX=
while [ $# -gt 0 ] && [ X"$1" != X"${1#-}" ]; do
	case "$1" in
	(-h|--help)     usage full     ;;
	(-V|--version)  usage version  ;;
	(-s|--suffix)   SUFFIX=.bak    ;;
	(-s?*)          SUFFIX=${1#-s} ;;
	(*) err "$1: unknown option;  type  $ARG0 --help  for help"
	esac
	shift
done


##
## Find first --
##
NUM=1
while [ $NUM -le $# ] && eval [ X\"\$$NUM\" -ne X-- ]; do
	NUM=$(( $NUM + 1 ))
done
[ $NUM -gt $# ] || err 'no -- given'
[ $NUM -ne 1  ] || err 'no command given'
[ $NUM -ne $# ] || err 'no files given'



##
## Temporary file
##
if [ -z "$SUFFIX" ]; then
	# Find temp dir
	TMPFILE=.
	for N in "$TMPDIR" "$TMP" "$TEMP" ~/tmp /tmp; do
		if [ -n "$N" ] && [ -d "$N" ] && [ -w "$N" ]; then
			TMPFILE="$N"
			break
		fi
	done

	# tempfile exists
	UMASK=$(umask)
	umask 077
	if which mktemp >/dev/null 2>&1; then
		TMPFILE=$(mktemp "$TEMPFILE/inplace-XXXXXXXX")
	elif which tempfile >/dev/null 2>&1; then
		TMPFILE=$(tempfile -d "$TEMPFILE" -p "inplace-")
	else
		err unable to create temporary file, mktemp or tempfile required
	fi

	trap 'rm -f -- "$TMPFILE"' 0
fi



##
## Main loop
##
N=1
for FILE in "$@"; do
	# Command
	if [ $N -lt $NUM ]; then
		eval CMD_$N=\$FILE
		N=$(( $N + 1 ))
		continue
	fi

	# --
	if [ $N -eq $NUM ]; then
		set --
		while [ $NUM -gt 1 ]; do
			NUM=$(( $NUM - 1 ))
			eval "set -- \"\$CMD_$NUM\" \"\$@\"; unset CMD_$NUM"
		done
		continue
	fi

	# File
	if [ -n "$SUFFIX" ]; then
		cp -fp -- "$FILE" "$FILE$SUFFIX" && "$@" <"$FILE$SUFFIX" >"$FILE"
	else
		"$@" <"$FILE" >"$TMPFILE" && cat <"$TMPFILE" >"$FILE"
	fi
done