TABLE OF CONTENTS
::pwtk::slurm_head
USAGE
   slurm_head { ...batch sh-script snippet here... }
EXAMPLE
   slurm_head {
      echo "Today is `date`"
      module load QuantumESPRESSO/7.3.1
   }
DESCRIPTION
This command sets the "head" part of the SLURM batch shell script. In PWTK, the batch shell script is composed of four parts:
        profile   (always exists)
         |
        head      (optional)
         |
        pwtk      (always exists)
         |
        tail      (optional)
where:
- profile -- contains the batch-queue directives (e.g. #SBATCH); it is set with slurm_profile command
 - head -- contains optional shell commands that are executed prior to executing PWTK, such as "module load ..."; it is set with slurm_head command
 - pwtk -- in this part, the PWTK script is executed; it is set internally by PWTK
 - tail -- contains optional shell commands that are executed after the PWTK script finishes; it is set with slurm_tail command