#include <stdio.h>#define KIBIBYTE_SIZE 1024LL#define MEBIBYTE_SIZE 1048576LL#define GIBIBYTE_SIZE 1073741824LL#define TEBIBYTE_SIZE 1099511627776LLtypedef 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 DigitUnitparse_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;intmeminfo (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;}

linux下读取系统内存的demo