Get the matching string prefix

Hi, I would like to exact the first X character of a string S1 where X is the lenght of a string S2. How to do that in shell ksh script

Here is my testing script

EEE=`echo $OUT_DATA | awk -F "ABC" '{printf("%s", $1)}'`
FFF=`echo $OUT_DATA | awk "ABC" '{printf("%s", $1)}'`

echo "EEE = $EEE"
echo "FFF = $FFF"

DDD=$(echo $OUT_DATA |awk '{print substr($0, 0 , 7))}')

Both EEE and FFF returns empty string.
DDD is okay, I am getting ABCDEFG back
But, how do i make it more dynamic? That is, somehow the length field in substr can
be determined based on the length of $MMM
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tommym121Author Commented:
Ah, I find a solution.

YY=`expr length $MMM`  
GGG=$(echo $OUT_DATA | cut -c1-$YY)
echo "GGG = $GGG"


Any better idea?

It works.

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EEE=`echo $OUT_DATA | awk -F "ABC" '{printf("%s", $2)}'`
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