I once did a small project, implemented in c languageCommodity Information Management System

I think everyone has done something similar

This project inevitably needs to enter characters from the keyboard

Choose an option

Then enter level by level

 

First level:

1. Product information added
 2. Product information inquiry
 3. Exit the system
 <Please enter options>:

 

second level:

1. Commodity price inquiry
 2. Query the place of production
 3. Exit to the previous level
 <Please enter options>:

 

Let's take a lookFake code

The pseudo code isCode that is not code, to explain the logic of your code

Generally, when the project starts to build, it will be a good tool

scanf(“%c”) Enter the first level of options

...

 scanf(“%c”) Enter the second level of options

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The question is coming! Focus!

When entering the first level of options

Your carriage return is also counted as a character, which is'\n'

There is one more character, it exists temporarilyBuffer zonein

When calling scanf for the second time, this carriage return character is used

So you can see that the scanf behind doesn't work anymore

 

AndOnly need to worry about this problem when the output format is %c

Other %s, %d, etc. don't have to worry about this problem!

the reason is simple

When I hit enter, I have knocked an extra'\n' into the buffer, but this'\n' is a character that can only be found by specifying the input format %c, so why don't worry about other input formats.

---

Solution

method 1:

getchar() method, but sometimes it can't be solved well

 

Method 2(recommend):

step one:

This function is used to clear the impact of the enter key cache, and add the definition of this function to the code

void safe_flush(FILE *fp)  
{  
    int ch;  
    while( (ch = fgetc(fp)) != EOF && ch != '\n' );   //end of file
}

Step two:

Before the scanf statement, you can call the function, and the function parameters are passed into the standard input (keyboard (stdin)).

safe_flush(stdin); //Keyboard: standard input file

scanf("%c",&c);

 

 

scanfSmall eggs:

1) When specifying the format, do not have a newline (\n) character.

2) If you want to enter multiple parameters, separate them with a space to form good habits. For example: scanf("%d %f",a,b);

3) Scanf format output can only specify the output width, not the output precision. For example, the wrong way of writing: scanf ("%.2f", &Money),I explained this in the previous section; 

 

 

Not easy to organize

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