Use correct CPU number

#!/bin/bash
#PBS -u user_name
#PBS -l nodes=1:ppn=8
#PBS -o $PBS_JOBNAME.out
#PBS -e $PBS_JOBNAME.err

#How many procs do I have?
NP=$(wc -l $PBS_NODEFILE | awk '{print $1}')

#cd into the directory where I typed qsub cd $PBS_O_WORKDIR

#run executable
mpiexec -np $NP executable