bulkrename

#!/bin/sh
# bulkrename: bulk rename files using $EDITOR and temporary files
# this file in public domain

EDITOR="${EDITOR:-"${VISUAL:-"vi"}"}"

err() {
	printf "%s: %s\n" "${0##*/}" "$@" >&2
	exit 1
}

hascollision() {
	i=0
	for arg
	do
		if test "$i" -lt "$nargs"
		then
			test "$target" = "$arg" && return
		else
			break
		fi
		i=$((i+1))
	done
	false
}

# create temporary files
if ! tmpfile="$(mktemp)"
then
	err "could not make temporary file"
fi
trap 'rm -f "$tmpfile"' EXIT

# if no argument is passed, fill $@ with lines from stdin
if [ $# -eq 0 ]
then                            # run on stdin
	while read -r line
	do
		set -- "$@" "$line"
	done
fi

# check if arguments are valid and write them to tmpfile
nargs="$#"
for arg
do
	case "$arg" in
	("")
		err "empty argument"
		;;
	(*[[:cntrl:]]*)
		err "control characters in filenames are not supported"
		;;
	([[:space:]]*|*[[:space:]])
		err "filenames beginning or ending in space is not supported"
		;;
	esac
	if ! test -e "$arg"
	then
		err "$arg: file does not exist"
	fi
	printf "%s\n" "$arg" >> "$tmpfile"
done

# call editor on tmpfile
"$EDITOR" -- "$tmpfile" </dev/tty

# read new filenames from edited tmpfile
while read -r target && test "$nargs" -gt 0
do
	source="$1"

	# for each target filename read from the file there is a
	# corresponding entry in $@.  We read filenames from the
	# file up to $nargs, and append $@ with commands:
	# "rm" "file"           (remove file)
	# "mv0" "from" "to"     (move file on the next loop)
	# "mv1" "from" "to"     (move file on the last loop)
	if test -z "$target"
	then
		# line asks to remove file
		set -- "$@" "rm" "$source"
	elif test "$target" = "$source"
	then
		# line does nothing
		:
	elif hascollision "$@"
	then
		# line renaming creates filename collision; get unique filename
		unique="$source"
		while test -e "$unique"
		do
			unique="$unique~"
		done
		set -- "$@" "mv0" "$source" "$unique"
		set -- "$@" "mv1"  "$unique" "$target"
	else
		# line is a renaming without collision
		set -- "$@" "mv0" "$source" "$target"
	fi

	# we're done with this source file
	shift
	nargs="$((nargs - 1))"
done <"$tmpfile"

# remove remaining arguments (in case file has more lines than we have files)
shift "$nargs"

# perform the commands specified in the argument list
while test "$#" -gt 0
do
	case "$1" in
	("rm")
		rm -- "$2"
		printf "rm %s\n" "$2"
		shift 2
		;;
	("mv0")
		mv -- "$2" "$3"
		printf "%s -> %s\n" "$2" "$3"
		shift 3
		;;
	("mv1")
		set -- "$@" "mv2" "$2" "$3"
		shift 3
		;;
	("mv2")
		break
		;;
	(*)
		err "$1: unknown command"
		;;
	esac
done

# perform the commands specified in the argument list (the final ones)
while test "$#" -gt 0
do
	case "$1" in
	("mv2")
		mv -- "$2" "$3"
		printf "%s -> %s\n" "$2" "$3"
		shift 3
		;;
	(*)
		err "$1: unknown command"
		;;
	esac
done