How to solve the problem that scanf return value is ignored

The solutions to the ignored return value of scanf include checking the return value of scanf, clearing the input buffer, and using fgets instead of scanf. Detailed introduction: 1. Check the return value of scanf. You should always check the return value of the scanf function. The return value of the scanf function is the number of successfully read parameters. If the return value is inconsistent with the expected one, it means that the input is incorrect; 2 , Clear the input buffer. When using the scanf function, if the input data does not match the expected format, the data in the input buffer will be lost, etc.

In C language, the return values ​​of functions are very important because they provide information about the results of function execution. However, when using the scanf function, we may encounter a situation where the return value of the function is ignored. This can lead to potential problems such as typos or an inability to read user input correctly. In order to solve this problem, we can take the following methods:

1. Check the return value of scanf: First, we should always check the return value of the scanf function. The return value of the scanf function is the number of parameters successfully read. If the return value is inconsistent with what we expect, it means that the input was incorrect. Therefore, we can use conditional statements to check the return value and take appropriate action. For example:

int num;
if(scanf("%d", &num) != 1){
    printf("输入有误！\n");
    // 处理输入错误的逻辑
}

In this example, if the scanf function cannot successfully read an integer, it will return 0. We can determine whether the input is incorrect by checking whether the return value is equal to 1.

2. Clear the input buffer: When we use the scanf function, if the input data does not match the format we expect, data will remain in the input buffer. This may cause problems with subsequent input operations. To solve this problem, we can clear the input buffer. This can be accomplished using the following code:

int c;
while ((c = getchar()) != '\n' && c != EOF) {}

This code reads characters from the input buffer until a newline character or end-of-file character is encountered. This ensures that no data remains in the input buffer.

3. Use fgets instead of scanf: Another solution is to use the fgets function to read user input. The fgets function can read a line of string and store it into the specified buffer. We can then use the sscanf function to parse the data we need from the buffer. This approach avoids some potential problems with the scanf function. The following is a sample code:

char buffer[100];
if(fgets(buffer, sizeof(buffer), stdin) != NULL){
    int num;
    if(sscanf(buffer, "%d", &num) != 1){
        printf("输入有误！\n");
        // 处理输入错误的逻辑
    }
}

In this example, we first use the fgets function to read the user input and store it in the buffer. We then use the sscanf function to parse the integers out of the buffer. If parsing fails, we can handle it as needed.

To sum up, when we use the scanf function, we should always check its return value to ensure the correctness of the input. In addition, we can also clear the input buffer or use the fgets function to avoid some potential problems. These methods will help us better handle and solve the problem of ignored scanf return values.

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