Shell Programming and Scripting

FILE1_LINES=$(wc -l file1 | awk '{print $1}')
FILE2_LINES=$(wc -l file2 | awk '{print $1}')
FILE3_LINES=$(wc -l file3 | awk '{print $1}')
MAX=$FILE1_LINES
if [ $MAX -lt $FILE2_LINES ]
then
 MAX=$FILE2_LINES
fi
if [ $MAX -lt $FILE3_LINES ]
then
 MAX=$FILE3_LINES
fi
awk 'BEGIN {OFS=","} {print $1,$2}' file1 >file11
awk 'BEGIN {OFS=","} {print $1,$2}' file2 >file21
awk 'BEGIN {OFS=","} {print $1,$2}' file3 >file31

FILE1_DEFICIT=$(expr $MAX - $FILE1_LINES)
while [ $FILE1_DEFICIT -gt 0 ]
do
 echo "," >>file11
 FILE1_DEFICIT=$(expr $FILE1_DEFICIT - 1)
done

FILE2_DEFICIT=$(expr $MAX - $FILE2_LINES)
while [ $FILE2_DEFICIT -gt 0 ]
do
 echo "," >>file21
 FILE2_DEFICIT=$(expr $FILE2_DEFICIT - 1)
done

FILE3_DEFICIT=$(expr $MAX - $FILE3_LINES)
while [ $FILE3_DEFICIT -gt 0 ]
do
 echo "," >>file31
 FILE3_DEFICIT=$(expr $FILE3_DEFICIT - 1)
done

paste -d, file11 file21 file31 >out.csv