sbatch - Dollar sign to get the value not working in my shell script?

Question

Our school uses SLURM as the queueing system, where one has to specify some "preambles" before other commands. Hence, a shell script in this case usually starts with

#!/bin/bash

#SBATCH -n 10               # Number of cores requested
#SBATCH -N 1                # Ensure that all cores are on one machine
#SBATCH -p general          # Partition to submit to
#SBATCH --mem-per-cpu=20000 # Memory per cpu in MB (see also --mem)
#SBATCH -o out              # Standard out goes to this file 

Now, I wish to make my core number as a constant, which facilitates modifications. I did

#!/bin/bash

ZEROTH_PORT=50000
NO_CORES=10

#SBATCH -n $((NO_CORES))    # Number of cores requested
#SBATCH -N 1                # Ensure that all cores are on one machine
#SBATCH -p general          # Partition to submit to
#SBATCH --mem-per-cpu=20000 # Memory per cpu in MB (see also --mem)
#SBATCH -o out              # Standard out goes to this file 

It fails at #SBATCH -n $((NO_CORES)). As a complete newbie in shell script, I have no idea why $((NO_CORES)) here returns the value of NO_CORES.

Answer 1

$(( … ))是算术评估上下文。由于NO_CORES是一个整数，并且在语法中没有对其进行任何其他操作，因此结果是 的扩展值NO_CORES。但是如果你知道参数是一个整数，你可以使用一个正常的扩展：

NO_CORES=10
SBATCH -n $NO_CORES # -> SBATCH -n 10