#include <stdio.h>

#define iskanji(c) ((c & 0xFF) >= 0x81 && (c & 0xFF) <= 0x9F || (c & 0xFF) >= 0xE0 && (c & 0xFF) <= 0xFC)
#define MOJI_LEN 8

int edit_string(char *) ;

main()
{
    //char str[] = "12345+67890+12345+67890" ;
    char str[] = "01+2345+6789" ;

    if (edit_string(str) != 0) {
        exit(-1) ;
    }
    printf("[%s]\n",str) ;

    exit(0) ;
}

int edit_string(char *str)
{
    char *p ;
    char wk_str[65] ;
    char c ;
    int i ;
    int j=0 ;

    memset(wk_str,'\0',sizeof(wk_str)) ;
    p = str ;

    for (i=0; *p;) {
        c = *p ;
        if (iskanji(c)) {
            return(-1) ;
        }

        if (*p >= 0x30 && *p <= 0x39) {
            wk_str[i++] = *p ;
            p++ ;
        } else {
            p++ ;
        }
    }

    if (strlen(wk_str) > MOJI_LEN) {
        p = str ;
        memset(wk_str,'\0',sizeof(wk_str)) ;

        while (*p) {
            if (*p < 0x30 || *p > 0x39) {
                p++ ;
                break ;
            }
            p++ ;
        }
        for (i=0; *p;) {
            if (*p >= 0x30 && *p <= 0x39) {
                wk_str[i++] = *p ;
                p++ ;
            } else {
                p++ ;
            }
            if (i > MOJI_LEN) {
                return(-1) ;
            }
        }
    }

    strncpy(str,wk_str,strlen(wk_str)) ;
    *(str+strlen(wk_str)) = '\0' ;

    return(0) ;
}

    for (i=0; *p;) {
        c = *p ;
        if (iskanji(c)) {
            return(-1) ;
        }

        if (*p >= 0x30 && *p <= 0x39) {
            wk_str[i++] = *p ;
            p++ ;
        } else {
            p++ ;
        }
    }

    for (i=0; *p; p++) {
        if (iskanji(*p)) return(-1) ;
        if (*p >= 0x30 && *p <= 0x39)
            wk_str[i++] = *p ;
    }

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

static int edit_string(char * s1, const char * s2, unsigned int size) ;
static int reverse(char * str, unsigned int n);

int 
main(void)
{
    //char str[] = "12345+67890+12345+67890" ;
    char str[] = "01+2345+6789" ;
    char buf[9];

    if (edit_string(buf,str,8) != 0) {
        return -1;
    }

    printf("[%s]\n",buf) ;
    return 0;
}

static int 
edit_string(char *s1, const char * s2, unsigned int size)
{
    char * p1 = s1;
    const char * p2 = s2 + strlen(s2);
    unsigned int i;

    // 文字列の後ろからsize文字取得
    for(i = 0; (p2 != s2) && (i < size); --p2) {
        if ('0' <= *p2 && *p2 <= '9') {
            *p1++ = *p2;
            ++i;
        }
    }

    // 配列を反転
    reverse(s1, i);

    // 終端文字の挿入
    *p1 = '\0';

    return 0 ;
}

static int 
reverse(char * str, unsigned int n)
{
    unsigned int i = 0;
    char ch;

    for(; i<n-1; ++i,--n) {
        ch = str[i];
        str[i] = str[n-1];
        str[n-1] = ch;
    }

    return 0;
}

#include <stdio.h>

#define MOJI_LEN 8

int edit_str(const char *s,char *rs)
{
    int i,c,n;
    for(i=0,c=0,n=0;s[i];i++)
        if(s[i]>='0'&&s[i]<='9') {
            if(c<=MOJI_LEN) rs[c++]=s[i];
        } else if(!n) n=i+1;
    if(c>MOJI_LEN) {
        if(n) return edit_str(s+n,rs);
        else return -1;
    }
    rs[c]='\0';
    return 0;
}

int main(void)
{
    char s[]="01+23456+789+0123455644",rs[MOJI_LEN+1];
    if(edit_str(s,rs)!=0) return -1;
    printf("%s",rs);
    return 0;
}

#include <stdio.h>

static int edit_string(char * s1, const char * s2, unsigned int size) ;

int 
main(void)
{
    //char str[] = "12345+67890+12345+67890" ;
    char str[] = "01+2345+6789" ;
    char buf[9];

    if (edit_string(buf,str,8) != 0) {
        return -1;
    }
    printf("[%s]\n",buf) ;
    return 0;
}

static int 
edit_string(char *s1, const char * s2, unsigned int size)
{
    char * p1 = s1;
    const char * p2 = s2;
    unsigned int i;

    do {
        for(p1 = s1,i = 0; *p2 && (i < size); ++p2) {
            if ('0' <= *p2 && *p2 <= '9') {
                *p1++ = *p2;
                ++i;
            }
        }
    }while(*p2);

    *p1 = '\0';
    return 0 ;
}