如何使用 scanf 从缓冲区中提取一些格式化的字符串？

Question

我需要从那个长字符串中提取 "rudolf" 和 "12"："hello, i know that rudolph=12 but it so small..." 使用 scanf，我该怎么做？

此缓冲区可以包含任何格式的字符串，如 ruby=45 或 bomb=1，我事先并不知道。

我正在尝试类似的方法，但没有成功

#include <stdio.h>

int main()
{
    char sentence[] = "hello, i know that rudolph=12 but it so small...";
    char name[32];
    int value;

    sscanf(sentence, "%[a-z]=%d", name, &value);
    printf("%s -> %d\n", name, value);

    getchar();
    return 0;
}

Answer 1

使用临时指针遍历句子并%n提取每个子字符串。
%n 将给出扫描到该点所处理的字符数。将其添加到临时指针以推进句子。
尝试从每个子字符串中解析名称和值。扫描集 %31[^=] 将扫描最多 31 个字符，在 name 中留出空间用于终止零。它将扫描所有不是 = 的字符。然后格式字符串将扫描 = 并尝试扫描一个整数。

#include <stdio.h>
#include <stdlib.h>

int main (void) {
    char sentence[] = "hello, i know that rudolph=12 but it so small...";
    char string[sizeof sentence] = "";
    char name[32] = "";
    char *temp = sentence;
    int value = 0;
    int count = 0;
    int parsed = 0;

    while (1 == sscanf(temp, "%s%n", string, &count)) {
        temp += count;
        if (2 == sscanf(string, "%31[^=]=%d", name, &value)) {
            parsed = 1;
            break;
        }
    }
    if (parsed) {
        printf("%s %d\n", name, value);
    }

    return 0;
}

Answer 2

您可以编写自己的字符串搜索引擎。这可能很简单，让我们举个例子：

前进，直到找到 [a-z] 之一
- 记住位置
- 前进到[a-z]
- 检查现在是否 =
  - 如果是，那就是我们的变量名
  - 前进到值结束
  - return它
如果没有 =，请忽略所有不是 [a-z] 的内容，即。不能是变量名

示例程序：

#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <string.h>

struct find_assignment_s {
    const char *line;
    const char *var;
    size_t varlen;
    const char *val;
    size_t vallen;
};

struct find_assignment_s find_assignment_init(const char *line) {
    return (struct find_assignment_s){.line = line};
}

int find_assignment(struct find_assignment_s *t) {
    while (*t->line) {
        const char *p = t->line;
        while (*p && isalpha((unsigned char)*p)) p++;
        // There is at least one alphabetic character and there is a space right after.
        if (t->line != p && *p == '=') {
            // Found a "variable="!
            t->var = t->line;
            t->varlen = p - t->line;
            // value is up until a space is found
            t->val = p + 1;
            while (*p && !isspace((unsigned char)*p)) p++;
            t->vallen = p - t->val;
            // Advance the pointer behind value.
            t->line = *p ? p + 1 : p;
            return 1;
        }
        // Ignore spaces
        while (*p && !isalpha((unsigned char)*p)) p++;
        // Advance over whole word.
        t->line = p;
    }
    return 0;
}

int main() {
    const char line[] =  "hello, i know that rudolph=12 but it so small... a=b c=d fdnajn=123";
    for (struct find_assignment_s fs = find_assignment_init(line);
            find_assignment(&fs) == 1; ) {
        printf("%.*s = %.*s\n", (int)fs.varlen, fs.var, (int)fs.vallen, fs.val);
    }
}

输出：

rudolph = 12
a = b
c = d
fdnajn = 123

如何使用 scanf 从缓冲区中提取一些格式化的字符串？

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