linux下读取系统内存的demo

#include <stdio.h>

#define KIBIBYTE_SIZE 1024LL
#define MEBIBYTE_SIZE 1048576LL
#define GIBIBYTE_SIZE 1073741824LL
#define TEBIBYTE_SIZE 1099511627776LL

typedef enum {
    DIGIT_UNIT_BYTE,
    DIGIT_UNIT_KIBIBYTE,
    DIGIT_UNIT_MEBIBYTE,
    DIGIT_UNIT_GIBIBYTE,
    DIGIT_UNIT_TEBIBYTE
} DigitUnit;

static char*
find_suffix (const char* str)
{
    while (str[0] != 0 && (isdigit (str[0]) || strchr(",.-", str[0]) || isspace (str[0])))
        str++;
    return (char *) str;
}

static char*
find_digit (const char* str)
{
    while (str[0] != 0 && (!isdigit (str[0])))
        str++;
    return (char *) str;
}

static DigitUnit
parse_unit_suffix (const char* suffix)
{
   if (strlen (suffix) > 0) {
        switch (tolower (suffix[0])) {
            case ‘b‘: return DIGIT_UNIT_BYTE;
            case ‘k‘: return DIGIT_UNIT_KIBIBYTE;
            case ‘m‘: return DIGIT_UNIT_MEBIBYTE;
            case ‘g‘: return DIGIT_UNIT_GIBIBYTE;
            case ‘t‘: return DIGIT_UNIT_TEBIBYTE;
        }
    }

    return -1;
}

long long unit_size (DigitUnit unit)
{
    switch (unit) {
        case DIGIT_UNIT_BYTE:
            return 1;
        case DIGIT_UNIT_KIBIBYTE:
            return KIBIBYTE_SIZE;
        case DIGIT_UNIT_MEBIBYTE:
            return MEBIBYTE_SIZE;
        case DIGIT_UNIT_GIBIBYTE:
            return GIBIBYTE_SIZE;
        case DIGIT_UNIT_TEBIBYTE:
            return TEBIBYTE_SIZE;
    }
}

typedef struct {
    long long total;
    long long used;
} MemInfo;

int
meminfo (MemInfo *meminfo)
{
    char line[128];
    FILE* fp;
    long long totalmem;
    long long usedmem;
    char *digit;
    char *suffix;

    totalmem = 0;
    usedmem = 0;
    digit = 0;
    suffix = 0;

    memset (line, 0, 128);
    fp = fopen ("/proc/meminfo", "rb");
    if (fp < 0) {
        return -1;
    }

    fgets (line, 128, fp);

    digit = find_digit (line);
    suffix = find_suffix (digit);

    if (sscanf (digit, "%d", &totalmem) == 1) {
        meminfo->total = totalmem * unit_size(parse_unit_suffix(suffix));
    }

    fgets (line, 128, fp);

    digit = find_digit (line);
    suffix = find_suffix (digit);

    if (sscanf (digit, "%d", &usedmem) == 1) {
        meminfo->used = usedmem * unit_size(parse_unit_suffix(suffix));
    }

    return 0;
}

int main()
{
    MemInfo mem;
    meminfo (&mem);

    printf ("total:%lld used:%lld\n", mem.total, mem.used);

    return 0;
}