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#!/bin/sh
countlines() {
local IFS input count tmp
input="$1"
count=0
IFS='
'
for tmp in $input; do
count=$(( $count + 1 ))
done
echo $count
}
if [ -z "$1" ]; then
echo "$0: must be executed with a crypto device as argument" >&2
exit 1
fi
if ! device=$(dmsetup --showkeys table 2> /dev/null | grep "^$1:"); then
echo "$0: failed to find $1 in dmtable" >&2
exit 1
fi
if [ -z "$device" ]; then
echo "$0: device $1 doesn't exist" >&2
exit 1
fi
count=$(countlines "$device")
if [ $count -ne 1 ]; then
echo "$0: more than one device match $1" >&2
exit 1
fi
eval set -- $device
type="$4"
key="$6"
if [ "$type" != "crypt" ]; then
echo "$0: device $1 is not a crypto device" >&2
exit 1
fi
echo -n "$key"
exit 0
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