user-0 提问: 求指教！关于malloc函数，以及指针的问题（我想是的）

回复:
user: user-0
content: 引用 15 楼 zhao4zhong1 的回复:printf里面的%和变量的一一对应关系 scanf里面的%和变量以及变量前加不加&的一一对应关系 是C代码中非常容易出错的地方，而且通常编译还不出错。 所以在编译源代码之前值得专门仔细检查一遍甚至多遍。  在每个最后不带\n的printf后面加fflush(stdout); 在每个不想受接收缓冲区旧内容影响的scanf前面加rewind(stdin); 另外请检查scanf的返回值。 谢谢您的指教！！我稍微理解了道理，而且我觉得scanf跟输入的是“%c”还是“%d”有很大的关系，当输入“%c”的时候，就要以习性全部输入，当是“%d”的时候可以用循环每按一次换行就输入一个数！！太谢谢您了！！

user: user-1
content: Format Specification Fields: scanf and wscanf Functions A format specification has the following form:  % [width] [{h | l | I64 | L}]type  The format argument specifies the interpretation of the input and can contain one or more of the following:   White-space characters: blank (' '); tab ('\t'); or newline ('\n'). A white-space character causes scanf to read, but not store, all consecutive white-space characters in the input up to the next non–white-space character. One white-space character in the format matches any number (including 0) and combination of white-space characters in the input.   Non–white-space characters, except for the percent sign (%). A non–white-space character causes scanf to read, but not store, a matching non–white-space character. If the next character in stdin does not match, scanf terminates.   Format specifications, introduced by the percent sign (%). A format specification causes scanf to read and convert characters in the input into values of a specified type. The value is assigned to an argument in the argument list.  The format is read from left to right. Characters outside format specifications are expected to match the sequence of characters in stdin; the matching characters in stdin are scanned but not stored. If a character in stdin conflicts with the format specification, scanf terminates, and the character is left in stdin as if it had not been read.  When the first format specification is encountered, the value of the first input field is converted according to this specification and stored in the location that is specified by the first argument. The second format specification causes the second input field to be converted and stored in the second argument, and so on through the end of the format string.  An input field is defined as all characters up to the first white-space character (space, tab, or newline), or up to the first character that cannot be converted according to the format specification, or until the field width (if specified) is reached. If there are too many arguments for the given specifications, the extra arguments are evaluated but ignored. The results are unpredictable if there are not enough arguments for the format specification.  Each field of the format specification is a single character or a number signifying a particular format option. The type character, which appears after the last optional format field, determines whether the input field is interpreted as a character, a string, or a number.   The simplest format specification contains only the percent sign and a type character (for example, %s). If a percent sign (%) is followed by a character that has no meaning as a format-control character, that character and the following characters (up to the next percent sign) are treated as an ordinary sequence of characters, that is, a sequence of characters that must match the input. For example, to specify that a percent-sign character is to be input, use %%.  An asterisk (*) following the percent sign suppresses assignment of the next input field, which is interpreted as a field of the specified type. The field is scanned but not stored.

user: user-1
content: printf里面的%和变量的一一对应关系 scanf里面的%和变量以及变量前加不加&的一一对应关系 是C代码中非常容易出错的地方，而且通常编译还不出错。 所以在编译源代码之前值得专门仔细检查一遍甚至多遍。  在每个最后不带\n的printf后面加fflush(stdout); 在每个不想受接收缓冲区旧内容影响的scanf前面加rewind(stdin); 另外请检查scanf的返回值。

user: user-2
content: 引用 12 楼 mujiok2003 的回复:[quote=引用 7 楼 u012686177 的回复:] [quote=引用 3 楼 user-4 的回复:] 输入q之后敲了个回车，被第二个scanf读到了。如果你用%d来输出*p，你会看到13 敲回车之前多输入几个字符就好了。 如果，我想循环输入多个字符，就不能像数组那样一个一个去接收吗？有没有改进的办法？[/quote] [/quote]  int n = 120; char* p = (char*)malloc(n) char fmt[64]; if(p) {   snprintf(fmt, 64, "%%%us", n-1); //%119s   scanf(fmt, p);  }

user: user-2
content: 引用 12 楼 mujiok2003 的回复:[quote=引用 7 楼 u012686177 的回复:] [quote=引用 3 楼 user-4 的回复:] 输入q之后敲了个回车，被第二个scanf读到了。如果你用%d来输出*p，你会看到13 敲回车之前多输入几个字符就好了。 如果，我想循环输入多个字符，就不能像数组那样一个一个去接收吗？有没有改进的办法？[/quote]  int n = 120; char* p = (char*)malloc(n) char fmt[64]; if(p) {   snprintf(fmt, 64, "%%%u", n-1); //%119s   scan(fmt, p);  } [/quote]  scan --> scanf

user: user-2
content: 引用 7 楼 u012686177 的回复:[quote=引用 3 楼 user-4 的回复:] 输入q之后敲了个回车，被第二个scanf读到了。如果你用%d来输出*p，你会看到13 敲回车之前多输入几个字符就好了。 如果，我想循环输入多个字符，就不能像数组那样一个一个去接收吗？有没有改进的办法？[/quote]  int n = 120; char* p = (char*)malloc(n) char fmt[64]; if(p) {   snprintf(fmt, 64, "%%%u", n-1); //%119s   scan(fmt, p);  }

user: user-3
content: 引用 8 楼 u012686177 的回复:[quote=引用 5 楼 lovesmiles 的回复:] 应该是第一次输入时按多了一次回车引起的 如果，我想循环输入多个字符，就不能像数组那样一个一个去接收吗？有没有好的改进办法？请多多指教！[/quote] for(int i=0;i<6;i++) scanf("%c",&p[i]); 这样你就可以一次性输入6个字符了。就像数组一样

user: user-4
content: scanf("%s", p); 是读取一个字符串，直到输入空格或回车。 但是要小心，如果输入的字符个数超过了p的长度，会导致数组越界。

user: user-4
content: 引用 7 楼 u012686177 的回复:[quote=引用 3 楼 user-4 的回复:] 输入q之后敲了个回车，被第二个scanf读到了。如果你用%d来输出*p，你会看到13 敲回车之前多输入几个字符就好了。 如果，我想循环输入多个字符，就不能像数组那样一个一个去接收吗？有没有改进的办法？[/quote] scanf("%s", p);

user: user-0
content: 引用 5 楼 lovesmiles 的回复:应该是第一次输入时按多了一次回车引起的 如果，我想循环输入多个字符，就不能像数组那样一个一个去接收吗？有没有好的改进办法？请多多指教！

user: user-0
content: 引用 3 楼 user-4 的回复:输入q之后敲了个回车，被第二个scanf读到了。如果你用%d来输出*p，你会看到13 敲回车之前多输入几个字符就好了。 如果，我想循环输入多个字符，就不能像数组那样一个一个去接收吗？有没有改进的办法？

user: user-0
content: 引用 4 楼 user-4 的回复:[quote=引用 3 楼 user-4 的回复:] 输入q之后敲了个回车，被第二个scanf读到了。如果你用%d来输出*p，你会看到13 也可能是10，\r和\n的ascii码我总是分不清。 [/quote]告诉我，你们怎么可以这么厉害。。。我以为是4字节指针和char类型的一字节有什么冲突呢 。。。关键是，我发的帖子，你都回啊！！好感动啊，大神！虽然我只发了两个帖子。。。

user: user-3
content: 应该是第一次输入时按多了一次回车引起的

user: user-4
content: 引用 3 楼 user-4 的回复:输入q之后敲了个回车，被第二个scanf读到了。如果你用%d来输出*p，你会看到13 也可能是10，\r和\n的ascii码我总是分不清。

user: user-4
content: 输入q之后敲了个回车，被第二个scanf读到了。如果你用%d来输出*p，你会看到13 敲回车之前多输入几个字符就好了。

user: user-0
content: 为什么我的第二次的scanf函数，在程序输入的时候，直接给我忽略了？？？

user: user-4
content: malloc/free要成对使用，分配了内存就要记得释放