ruby/tool/ifchange

#!/bin/sh
# usage: ifchange target temporary

set -e
timestamp=
keepsuffix=
empty=
color=auto
until [ $# -eq 0 ]; do
    case "$1" in
	--timestamp)
	    timestamp=.
	    ;;
	--timestamp=*)
	    timestamp=`expr \( "$1" : '[^=]*=\(.*\)' \)`
	    ;;
	--keep)
	    keepsuffix=.old
	    ;;
	--keep=*)
	    keepsuffix=`expr \( "$1" : '[^=]*=\(.*\)' \)`
	    ;;
	--empty)
	    empty=yes
	    ;;
	--color)
	    color=always
	    ;;
	--color=*)
	    color=`expr \( "$1" : '[^=]*=\(.*\)' \)`
	    ;;
	*)
	    break
	    ;;
    esac
    shift
done

target="$1"
temp="$2"
if [ "$temp" = - ]; then
    temp="tmpdata$$.tmp~"
    cat > "$temp"
    trap 'rm -f "$temp"' 0
fi

msg_begin= msg_unchanged= msg_updated= msg_reset=
if [ "$color" = always -o \( "$color" = auto -a -t 1 \) ]; then
    msg_begin="["
    case "`tput smso 2>/dev/null`" in
	"$msg_begin"*m)
	    if [ ${TEST_COLORS:+set} ]; then
		msg_unchanged=`expr ":$TEST_COLORS:" : ".*:pass=\([^:]*\):"` || :
		msg_updated=`expr ":$TEST_COLORS:" : ".*:fail=\([^:]*\):"` || :
	    fi
	    msg_unchanged="${msg_begin}${msg_unchanged:-32;1}m"
	    msg_updated="${msg_begin}${msg_updated:-31;1}m"
	    msg_reset="${msg_begin}m"
	    ;;
    esac
    unset msg_begin
fi

targetdir=
case "$target" in */*) targetdir=`dirname "$target"`;; esac
if [ -f "$target" -a ! -${empty:+f}${empty:-s} "$temp" ] || cmp "$target" "$temp" >/dev/null 2>&1; then
    echo "$target ${msg_unchanged}unchanged${msg_reset}"
    rm -f "$temp"
else
    echo "$target ${msg_updated}updated${msg_reset}"
    [ x"${targetdir}" = x -o -d "${targetdir}" ] || mkdir -p "${targetdir}"
    [ x"${keepsuffix}" != x -a -f "$target" ] && mv -f "$target" "${target}${keepsuffix}"
    mv -f "$temp" "$target"
fi

if [ -n "${timestamp}" ]; then
    if [ x"${timestamp}" = x. ]; then
	if [ x"$targetdir" = x. ]; then
	    timestamp=.time."$target"
	else
	    timestamp="$targetdir"/.time.`basename "$target"`
	fi
    fi
    : > "$timestamp"
fi