如何在C中输入和扫描多个字符 [英] How to enter and scan multiple chars in c

问题描述

我想输入多个printfs，但是我没有机会输入. 我只能输入1，但之后它才结束程序.我尝试了do，但没有用

I want to enter multiple printfs but i dont get opportunity to enter. I can enter only 1, but after that it just ends the programme.I tried with do while but it didnt work

int main()
{
  int number;
  char username[30]="";
  char fullName[30]="";
  char password[30]="";
  printf("Do you want to log in(1) or register (2)? \n");  
  scanf("%d",&number);
  if (number==2)
  {
    printf("username : ");
    scanf("%s",&username);
    printf("Full name : ");
    scanf("%s",&fullName);
    printf("Password : ");
    scanf("%s",&password);
    printf("Repeat password : ");
    scanf("%s",&password);
  }
  return 0;
}

推荐答案

我只能输入1，但之后它会结束程序.

I can enter only 1, but after that it just ends the programme.

当然，因为代码具有if (number==2)

Of course, as the code has if (number==2) @Scadge

如果输入"2"，请考虑以下事项:

If you enter "2", consider the following:

scanf("%s",&fullname);不会将空格或其他空白保存到fullname中.输入全名(例如"John Doe")会将"John"保存到fullname，将"Doe"保存到password.

scanf("%s",&fullname); will not save spaces or other white-spaces into fullname. Entering a full name like "John Doe" will save "John" into fullname and "Doe" into password.

避免使用scanf().

使用fgets()读取用户输入，而不是使用scanf()来读取用户输入.这是可以处理各种输入问题的辅助功能的绝佳机会.

Rather than use scanf() to read user input, read user input with fgets(). This is a fine opportunity for helper functions that can handle various input issues.

int read_int(const char *prompt) {
  if (prompt) fputs(prompt, stdout);
  fflush(stdout);  // insure output is written before asking for input

  char buffer[40];
  if (fgets(buffer, sizeof buffer, stdin) == NULL) {
    return NULL;
  }

  int i;
  if (sscanf(buffer, "%d", &i) == 1) {
    return i;
  }

  // TBD - what should code do if invalid data entered.  Try again?
}

char *read_line(char *dest, sizeof size, const char *prompt) {
  if (prompt) fputs(prompt, stdout);
  fflush(stdout);  // insure output is written before asking for input

  char buffer[size * 2 + 1];  // form buffer at _least 1 larger for \n
  if (fgets(buffer, sizeof buffer, stdin) == NULL) {
    return NULL;
  }

  size_t len = strlen(buffer);
  if (len > 0 && buffer[len-1] == '\n') buffer[--len] = '\0';

  if (len >= size) {
    // input too big - how do you want to handle this?
    TBD_Code();
  } 
  return strcpy(dest, buffer);
}

现在使用这2个帮助器功能进行简洁的用户输入

Now use these 2 helper functions for clean user input

// printf("Do you want to log in(1) or register (2)? \n");  
// scanf("%d",&number);
number = read_int("Do you want to log in(1) or register (2)? \n");

...

// printf("username : ");
// scanf("%s",&username);
read_line(username, sizeof username, "username : ");
// printf("Full name : ");
// scanf("%s",&fullName);
read_line(fullName, sizeof fullName, "fullName : ");

可以添加其他代码来检查文件结尾，超长行，int范围测试等.

Additional code could be added to check for end-of-file, extremely long lines, int range testing, etc.

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