转换说明符(%s、%u、%c.....)

（图片转自网络）

十六进制输出   %x

printf("%x %X %#x",31,31,31);    //1f 1F 0x1f

整数的左、右宽度

 NSString *aa = [NSString stringWithFormat:@"%10d",100];    //       100  右移10个字符位置宽    NSString *aaa = [NSString stringWithFormat:@"%-10d",100];    //100         左移10个字符位置宽

//限制字符串输出 (小数点左边为总宽，右边为输出长度) 

    const char *cc = "A good girl tell me that.....I V U";    printf("%.11s\n%35s\n%36s\n%37s\n%-37s",cc,cc,cc,cc,cc);    /*     A good girl      A good girl tell me that.....I V U       A good girl tell me that.....I V U        A good girl tell me that.....I V U     A good girl tell me that.....I V U   (lldb)     */