一个关于scanf()函数的问题

[Kris_Yang_2016]

各位大神，有一个问题想请教一下，谢谢~

在下面这段代码中，是怎么做到把secret.txt文件（见提问末）中的单词一个一个输入到word中的。
是不是因为有while语句的原因呢？
但是我还是不太懂while语句怎么做到把单词分开的。


代码如下：
#include <stdio.h>
int main()
{
char word[10];
int i = 0;
freopen("secret.txt","r",stdin);
freopen("message1.txt","w",stdout);
freopen("message2.txt","w",stderr);
while (scanf("%9s", word) == 1) {
i = i + 1;
if (i%2)
fprintf (stdout, "%s\n", word);
else
fprintf(stderr, "%s\n", word);
}
freopen("con", "r", stdin);
return 0;
}

secret.txt文件：
THE BUY SUBMARINE SIX WILL EGGS SURFACE AND AT SOME NINE MILK PM

[ghx287524027]

先要了解stdin、stdout、stderr，即标准输入，标准输出，标准错误。然后使用scanf函数从缓冲区内读取内容，读取的最大长度为9个字符（char word[10]的最后一位要存储字符串结束符），然后利用fprintf 函数输入到manager1和manager2中（第偶数个单词输入到message1.txt，第奇数个单词输入到message2.txt中）

[ghx287524027]

引用 1 楼 ghx287524027 的回复:

先要了解stdin、stdout、stderr，即标准输入，标准输出，标准错误。然后使用scanf函数从缓冲区内读取内容，读取的最大长度为9个字符（char word[10]的最后一位要存储字符串结束符），然后利用fprintf 函数输入到manager1和manager2中（第偶数个单词输入到message1.txt，第奇数个单词输入到message2.txt中）

应该是第奇数个单词输入到message1.txt，第偶数个单词输入到message2.txt

[小灸舞]

scanf("%9s", word) 表示最多拷贝9个字符
可以在格式化字符串中的"%"各格式化规定符之间加入一个整数，表示任何读操作中的最大位数。

[paschen]

http://en.cppreference.com/w/c/io/fscanf

[赵4老师]

作为一个C程序员，对 scanf,sscanf,fscanf printf,sprintf,fprintf 这类函数的用法，还是要做到“拳不离手，曲不离口”的。

[Kris_Yang_2016]

引用 1 楼 ghx287524027 的回复:

先要了解stdin、stdout、stderr，即标准输入，标准输出，标准错误。然后使用scanf函数从缓冲区内读取内容，读取的最大长度为9个字符（char word[10]的最后一位要存储字符串结束符），然后利用fprintf 函数输入到manager1和manager2中（第偶数个单词输入到message1.txt，第奇数个单词输入到message2.txt中）

举个例子啊，比如第一次读取的时候，读取了9个字符，word中不应该是THE BUY /n吗，输入到message1种的不也应该是THE BUY /n吗，但是实际上空格起到了分隔的作用，这是为什么。

[Kris_Yang_2016]

引用 3 楼 qq423399099 的回复:

scanf("%9s", word) 表示最多拷贝9个字符 可以在格式化字符串中的"%"各格式化规定符之间加入一个整数，表示任何读操作中的最大位数。

举个例子啊，比如第一次读取的时候，读取了9个字符，word中不应该是THE BUY /n吗，输入到message1种的不也应该是THE BUY /n吗，但是实际上空格起到了分隔的作用，这是为什么。

[小灸舞]

引用 7 楼 Kris_Yang_2016 的回复:

[quote=引用 3 楼 qq423399099 的回复:] scanf("%9s", word) 表示最多拷贝9个字符 可以在格式化字符串中的"%"各格式化规定符之间加入一个整数，表示任何读操作中的最大位数。

举个例子啊，比如第一次读取的时候，读取了9个字符，word中不应该是THE BUY /n吗，输入到message1种的不也应该是THE BUY /n吗，但是实际上空格起到了分隔的作用，这是为什么。[/quote] scanf不能读入空格，空格会被当做空白符（空格(space)、制表符(tab)和新行符(newline)）达到分隔的作用

[赵4老师]

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. 不要迷信书、考题、老师、回帖； 要迷信CPU、编译器、调试器、运行结果。 并请结合“盲人摸太阳”和“驾船出海时一定只带一个指南针。”加以理解。 任何理论、权威、传说、真理、标准、解释、想象、知识……都比不上摆在眼前的事实！