>>474
#include <stdio.h>
#include <ctype.h>

char* extract_num(const char* source, char* dest)
{
    char* p = dest;
    while (*source++) if (isdigit(*source)) *p++ = *source;
    *p = '\0';
    return dest;
}

int main()
{
    const char s[] = "aaa012345 145";
    char d[256];
    printf("%s", extract_num(s, d));
}