Question

我想从字符串中提取单词。

我不想使用strtok因为它会破坏我的源字符串。另一件事是，我想知道是否有可能设法做我想要的而不使用循环。

这是我的代码示例。它成功地读取了第一个单词，但第二个和第三个单词仍为空。

char source[] = "XXX|YYY|ZZZ";

char word1[10] = "";
char word2[10] = "";
char word3[10] = "";

sscanf( source, "%[^|]s|%[^|]s|%s", word1, word2, word3 );

是否真的有可能使用sscanf或我走错路？

更新

看起来user3121023的答案对空单词不起作用。

char source[] = "XXX||ZZZ";

char word1[10] = "";
char word2[10] = "";
char word3[10] = "";

sscanf( source, "%[^|]|%[^|]|%s", word1, word2, word3 );

第三个字仍为空。我该怎么做才能做到这一点？

Answer 1

Your sscanf() format does not empty substrings, neither does it protect against potential buffer overflows if the target arrays are smaller than the source string.

Here is a solution with strcspn() and a utility function strcpy_n:

#include <string.h>

char *strcpy_n(char *dest, size_t size, const char *src, size_t n) {
    if (size > 0) {
        if (n >= size)
            n = size - 1;
        memcpy(dest, src, n);
        dest[n] = '\0';
    }
    return dest;
}

...

    char source[] = "XXX||ZZZ";
    char word1[10], word2[10], word3[10] = "";

    size_t pos = 0, len;

    len = strcspn(source + pos, "|");
    strcpy_n(word1, sizeof(word1), source + pos, len);
    pos = pos + len + (source[pos + len] == '|');

    len = strcspn(source + pos, "|");
    strcpy_n(word2, sizeof(word2), source + pos, len);
    pos = pos + len + (source[pos + len] == '|');

    len = strcspn(source + pos, "|");
    strcpy_n(word3, sizeof(word3), source + pos, len);
    pos = pos + len + (source[pos + len] == '|');

...

You can wrap the above code into another utility function getfield() to factor more code:

/* returns non zero if there are more fields to parse */
int getfield(char *dest, size_t size, const char *source, size_t *ppos) {
    int has_separator = 0;
    size_t pos = *ppos;
    size_t len = strcspn(source + pos, "|");
    strcpy_n(dest, size, source + pos, len);
    pos += len;
    has_separator = (source[pos] == '|');
    *ppos = pos + has_separator;
    return has_separator;
}

 ...

    char source[] = "XXX||ZZZ";
    char word1[10], word2[10], word3[10];

    size_t pos = 0;

    /* parse the fields, empty and missing fields are set to "" */
    getfield(word1, sizeof(word1), source, &pos);
    getfield(word2, sizeof(word2), source, &pos);
    getfield(word3, sizeof(word3), source, &pos);

...

使用sscanf从字符串中提取（可能为空）单词（由＆＃34; |＆＃34;分隔）

1 个答案: