trim() 用于删除字符串尾部的空格符、制表符与换行符

/* trim:  remove trailing blanks, tabs, newlines */
int trim(char s[])
{
        int n;
    for (n = strlen(s)-1; n >= 0; n--)
                if (s[n] != ' ' && s[n] != '\t' && s[n] != '\n')
                        break;
    s[n+1] = '\0';
    return n;
}