strspn&strcspn

size_t strspn (const char *s,const char * accept);

strspn返回s中第一个不在accept中出现过的字符下标。

Returns an integer value specifying the length of the substring in str that consists entirely of characters in strCharSet.

If str begins with a character not in strCharSet, the function returns 0.

accept可以包含多个字符，从str开始搜索，计算str中包含的accept中任一字符的下标。

#include <string.h>
#include <stdio.h>
main()
{
    char *str="Linux was first developed for 386/486-based pcs.";
    printf("%d\n",strspn(str,"Linux"));
    printf("%d\n",strspn(str,"/-"));
    printf("%d\n",strspn(str,""));
}

运行结果：

5

0

0

 

size_t strcspn(const char *s, const char * reject);

strcspn()从参数s 字符串的开头计算连续的字符, 而这些字符都完全不在参数reject 所指的字符串中.

简单地说, 若strcspn()返回的数值为n, 则代表字符串s 开头连续有n 个字符都不含字符串reject 内的字符.

返回字符串s 开头连续不含字符串reject 内的字符数目，也即返回s中第一个在reject中出现过的字符下标。

#include <string.h>

main(void)

{

    char *str = "Linux was first developed for 386/486-based pcs. ";

    printf("%d\n", strcspn(str, " "));

    printf("%d\n", strcspn(str, "/-"));

    printf("%d\n", strcspn(str, ""));

}
 

运行结果：

5

33

30

编程使用：key-value去掉参数前面的空格

int _nvram_init(void *unused)
{
    FILE *in;
    char buffer[SIZE], *token, *line;
    int i;
    if (!(in = fopen(PATH_DEV_NVRAM, "r"))) {
        printf("nvram file can not open\n");
        return -;
    } 

    while (fgets(buffer, 300, in)) {
        if (strchr(buffer, '\n')) *(strchr(buffer, '\n')) = '\0';
        token = buffer + strspn(buffer, " ");
        if (*token == '\0') continue;
        line = token + strcspn(token, "=");
        if (*line == '\0') continue;
        *line = '\0';
        line++;

        /* eat leading whitespace */
        line = line + strspn(line, " ");
        /* eat trailing whitespace */
        for (i = strlen(line); i > 0 && (line[i - 1]==' '); i--);
        line[i] = '\0';
        _nvram_set(token,line);
    }
    fclose(in);
    printf("nvram init----\n");

    return 0;

}