Hello all,
I am not getting this error.
Pls help me.

Code:

./construct_operon.sh: line 5: [: -gt: unary operator expected

#!/bin/bash
# Construct Operons using gene pairs.
rm -rf operons_result
lines=`awk 'END {print NR}' ecoli_operons`
while [ $lines -gt 0 ];
do
    head -1 ecoli_operons | awk '{print $1"\n"$2}' > pattern
    grep -f pattern ecoli_operons | awk '{print $1"\n"$2}' > temp
    pat_count=`grep -f pattern -v temp | awk 'END {print NR}'`
    while [ $pat_count -gt 0 ];
    do
        cat temp >> pattern
        grep -f pattern ecoli_operons | awk '{print $1"\n"$2}' > temp
        pat_count=`grep -f pattern -v temp | awk 'END {print NR}'`
    done
    grep -f pattern ecoli_operons | awk '{print $1"\n"$2}' | sort -u | awk '{printf $0"\t"} END {printf"\n"}' >> operons_result
    grep -f pattern -v ecoli_operons > temp1
    mv temp1 ecoli_operons
    echo $lines
    lines=`awk 'END {print NR}' ecoli_operons`
done
rm -rf temp
rm -rf pattern