stressapptest源码剖析：默认参数和参数解析

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <getopt.h>
 
#define VERSION "1.0"
#define DEFAULT_DURATION 10
#define DEFAULT_DELAY 0
#define DEFAULT_CPU_STRENGTH 2
#define DEFAULT_IO_STRENGTH 1
#define DEFAULT_VM_STRENGTH 1
#define DEFAULT_VM_LINES 256
#define DEFAULT_FILE_SIZE 1024
#define DEFAULT_MEM_PATH "/dev/mem"
#define DEFAULT_MEM_OFFSET 0
#define DEFAULT_MEM_MASK 0
#define DEFAULT_HELP_MESSAGE 0
#define DEFAULT_VERBOSE 0
 
// 全局变量，用于保存解析后的参数值
int duration = DEFAULT_DURATION;
int delay = DEFAULT_DELAY;
int cpu_strength = DEFAULT_CPU_STRENGTH;
int io_strength = DEFAULT_IO_STRENGTH;
int vm_strength = DEFAULT_VM_STRENGTH;
int vm_lines = DEFAULT_VM_LINES;
int file_size = DEFAULT_FILE_SIZE;
char *mem_path = DEFAULT_MEM_PATH;
unsigned long mem_offset = DEFAULT_MEM_OFFSET;
unsigned long mem_mask = DEFAULT_MEM_MASK;
int help_message = DEFAULT_HELP_MESSAGE;
int verbose = DEFAULT_VERBOSE;
 
// 参数解析函数
void parse_args(int argc, char **argv) {
    int opt;
    while ((opt = getopt(argc, argv, "d:i:c:m:l:f:s:p:o:a:u:vhV")) != -1) {
        switch (opt) {
            case 'd':
                duration = atoi(optarg);
                break;
            case 'i':
                delay = atoi(optarg);
                break;
            case 'c':
                cpu_strength = atoi(optarg);
                break;
            case 'm':
                io_strength = atoi(optarg);
                break;
            case 'l':
                vm_strength = atoi(optarg);
                break;
            case 'f':
                file_size = atoi(optarg);
                break;
            case 's':
                vm_lines = atoi(optarg);
                break;
            case 'p':
                mem_path = optarg;
                break;
            case 'o':
                mem_offset = strtoul(optarg, NULL, 0);
                break;
            case 'a':
                mem_mask = strtoul(optarg, NULL, 0);
                break;
            case 'u':
                // 此处假设有一个函数parse_units用于解析时间单位
                duration = parse_units(optarg);
                break;
            case 'v':
                verbose = 1;
                break;
            case