C语言 scanf 读取“Enter”键
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scanf reading "Enter" key
提问by vs06
Why scanf doesn't work when I type "Enter" in the code below?
为什么当我在下面的代码中输入“Enter”时 scanf 不起作用？
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
int main(int argc, char**argv)
{
char *msg = malloc(100*sizeof(char));
do{
scanf("%s",msg);
printf("%s\n",msg);
} while(strcmp(msg,"")!=0);
}
回答by chux - Reinstate Monica
The "%s"in scanf("%s",...skips over leading whitespace (including "Enter" or \n) and so patiently waits for some non-whitespace text.
将"%s"在scanf("%s",...对领导空格跳跃（包括“回车”或\n）等耐心地等待一些非空白文本。
Best to take in a \n, use fgets()as suggested by @maxihatop
最好按照@maxihatop 的建议\n使用a ，使用fgets()
fgets(msg, 100, stdin);
If you needto use scanf()
如果您需要使用scanf()
int result = scanf("%99[^\n]%*c", msg);
if (result != 1) handle_IOError_or_EOF();
This will scan in 1 to 99 non-\nchars and then append a \0. It will then continue to scan 1 more char(presumably the \n) but not save it due to the *. If the first character is a '\n', msgis not changed and the '\n'remains in stdin.
这将扫描 1 到 99 个非\n字符，然后附加一个\0. 然后它将继续扫描 1 个char（大概是\n），但由于*. 如果第一个字符是'\n',msg则不会改变，而'\n'保留在stdin.
Edit (2016): To cope with lines that begin with '\n', separate the scan that looks for the trailing '\n'.
编辑（2016 年）：要处理以 开头的行，'\n'请将查找尾随的扫描分开'\n'。
msg[0] = 'fgets(msg, 100, stdin);
';
int result = scanf("%99[^\n]", msg);
scanf("%*1[\n]");
if (result == EOF) handle_IOError_or_EOF();
回答by olegarch
Because of scanf() wait char-string, separated by whitespaces, enters, etc. So, it just ignores ENTERs, and waiting for "real non-empty string". If you want to get empty string too, you need to use
由于 scanf() 等待字符字符串，由空格分隔，输入等。因此，它只是忽略 ENTER，并等待“真正的非空字符串”。如果你也想得到空字符串，你需要使用
##代码##回答by PandaRaid
Scanf looks through the input buffer for the specified format, which is string in this case. This has the effect of skipping your whitespaces. If you put a space between wording, it skips the space looking for the next string, similarly it will skip tabs, newlines etc. See what happens if you put a %c instead. It will pick up the newline because it is searching for a char now, and '\n' constitutes as a valid char.
Scanf 在输入缓冲区中查找指定格式，在本例中为字符串。这具有跳过空格的效果。如果你在措辞之间放置一个空格，它会跳过寻找下一个字符串的空格，类似地它会跳过制表符、换行符等。看看如果你放一个 %c 会发生什么。它将拾取换行符，因为它现在正在搜索一个字符，并且 '\n' 构成一个有效的字符。
If you want the same effect while getting whitespace, change it to a %c and remove the newline escape character at the print statement.
如果在获取空格时想要相同的效果，请将其更改为 %c 并删除打印语句中的换行符转义字符。
