nvram

#!/bin/sh
# nvram emulation shell script (c) kost, https://gist.github.com/kost
#
# Usage (on real device dump the content): nvram show > /tmp/nvram.file
# Copy script and /tmp/nvram.file to the emulation env, start using it
# In case you just need nvram command emulation, just copy script.
#
# uncomment for debug:
# set -x

show_usage() {
	echo "usage: nvram [get name] [set name=value] [unset name] [commit] [show]"
	return
}

if [ "$NVRAMFILE" = "" ]; then
	NVRAMFILE="/tmp/nvram.file"
fi

if [ "$1" = "" ]; then
	show_usage
fi

NVRAMCOMMIT="$NVRAMFILE.commit"

if [ -f "$NVRAMCOMMIT" ]; then
	NVRAMACT="$NVRAMCOMMIT"
else
	NVRAMACT="$NVRAMFILE"
fi

if [ "$1" = "show" ]; then
	cat $NVRAMACT
fi

if [ ! -f "$NVRAMFILE" ]; then
	touch "$NVRAMFILE" && (echo "Created $NVRAMFILE" >&2 )
fi

if [ "$1" = "commit" ]; then
	if [ -f "$NVRAMFILE.commit" ]; then
		cp $NVRAMFILE.commit $NVRAMFILE && rm -f $NVRAMFILE.commit
	fi
fi

if [ "$1" = "get" ]; then
	if [ "$2" = "" ]; then
		show_usage
	else
		grep "^$2=" $NVRAMACT | head -1 | cut -f2- -d=
	fi
fi

# we need tmp file for these commands
# mktemp would be better, but not portable (race cond)
NVRAMTMP="$NVRAMCOMMIT.$$"

if [ "$1" = "unset" ]; then
	if [ "$2" = "" ]; then
		show_usage
	else
		grep -v "^$2=" $NVRAMACT > $NVRAMTMP
		cp $NVRAMTMP $NVRAMCOMMIT && rm $NVRAMTMP
	fi
fi

if [ "$1" = "set" ]; then
	if [ "$2" = "" ]; then
		show_usage
	else
		NVRAMKEY=$(echo "$2" | cut -f1 -d=)
		NVRAMVALUE=$(echo "$2" | cut -f2- -d=)
		grep -v "^$NVRAMKEY=" $NVRAMACT > $NVRAMTMP
		echo "$2" >> $NVRAMTMP
		cp $NVRAMTMP $NVRAMCOMMIT && rm $NVRAMTMP
	fi
fi