Detailed explanations of%*d,%.*s, etc. of [C language]: "recommended collection"

Hello everyone , I meet you again , I'm your friend, Quan Jun .

Catalog ：

• 0. Preface 【 Lite version 】：
  • Less time to see here ：
• 1.【 Gentlemen and ladies stop ！！！！】
  • 0. Necessary introductory knowledge ：
  • 1. On the subject 1：scanf
    • (1) %*d Shot dead ：
    • (2) 【%.*d 】 My teammate was shot ：
  • 2. On the subject 2：printf I won't talk about it , Ahead 【 Preface 】 It seems to be very clear .

0. Preface 【 Lite version 】：

In fact, there are many explanations about this on the Internet , But it always makes novices and even young veterans a little confused , For example, there is an explanation on the Internet that ： Ignore …… What are you ignoring? You …

Less time to see here ：

%\* and \*.* In the form of , Generally, there are only integers % And string %s Is more useful , But for your convenience , Here I list all the basic information ：

Please note that ：scanf and printf The situation in is different ！

<1>scanf： Be careful ： stay scanf Only in Li %*d and %.*d meaningful , Other %*f,%*lf,%*c and %*s And so on are meaningless , The compiler will report an error . So don't Scribble .

(1) %*d( Only it makes sense ： Ignore itself , And re match ：)

int a=0,b=0,c=0;       

scanf("%*d%d%d",&a,&b,&c);
printf("a=%d,b=%d,c=%d",a,b,c);

 Input ：12  34  56
 Output ：a=34,b=56,c=0
 amount to ： Ignore the first input 12( It itself ),
 And will a Match the second number ,b And the third number ,
 therefore c No matching input , so c It's still the original value 0.

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Below 2 For your reference ：

/****************************************/
scanf("%d%*d%d",&a,&b,&c);
printf("a=%d,b=%d,c=%d",a,b,c);
 Input ：12  34  56
 Output ：a=12,b=56,c=0
 amount to ： Ignore the second input 34( It itself )
   
scanf("%d%d%*d",&a,&b,&c);
printf("a=%d,b=%d,c=%d",a,b,c);
 Input ：12  34  56
 Output ：a=12,b=34,c=0
 amount to ： Ignore the third input 56( It itself )

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(2) %.*d( Only it makes sense ： Ignore %*d The next input of , And re match )

scanf("%.*d%d%d",&a,&b,&c);
printf("a=%d,b=%d,c=%d",a,b,c);
 Input ：12  34  56
 Output ：a=12,b=56,c=0
 amount to ： Ignore the second input 34( It's next )
 therefore a Match the first input ,b Match the third input ,
 The input in the middle is ignored , therefore c There is no match .

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Below 2 For your reference ：

/****************************************/
scanf("%d%.*d%d",&a,&b,&c);
printf("a=%d,b=%d,c=%d",a,b,c);
 Input ：12  34  56
 Output ：a=12,b=34,c=0
 amount to ： Ignore the third input 56( It's next )

scanf("%d%d%.*d",&a,&b,&c);
printf("a=%d,b=%d,c=%d",a,b,c);
 Input ：12  34  56
 Output ：a=12,b=34,c=56
 amount to ： Ignore the fourth input ( It's next ： air )
 So the last one is meaningless ！ And no .* equally .

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<2>printf： Be careful ： stay printf There are no restrictions ,%c,%d,%s,%f,%lf You can add * or .*, It makes sense . however , Their meanings are different ：

(1) %*d( significance ： It will definitely output all , Fill in the blanks according to the actual situation )

int a=123;     

printf("a=%*d",2,a);
 Output ：a=123  
( Output all 123, length >2, There is no need to fill in blanks )
 It's the same as not specified ！

printf("a=%*d",10,a);
 Output ：a= Space, space, space, space, space 123    
( Fill forward 7 A space , Make up for the total 10 bits )

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(2) %.*d( significance ： It will definitely output results , Fill in the front according to the actual situation 0)

printf("a=%.*d",2,a);
 Output ：a=123  
( Output all 123, length >2, There is no need to mend 0)
 It's the same as not specified ！

printf("a=%.*d",10,a);
 Output ：a=0000000123    
( Fill forward 7 individual 0, Make up for the total 10 bits )

 Obviously, this situation is of little significance , Because we seldom need to make up 0.
 So this kind of writing is basically not used .

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(3) %*f( significance ： It will definitely output all , Fill in the blanks according to the actual situation ) Be careful ,%f The default is after the decimal point 6 digit ： The decimal point is one place ！

float a=12;
printf("a=%*f",3,a);
 Output ：a=123.000000
 The default is after the decimal point 6 position . And it will definitely output all ,
 therefore 10 position > designated 3 position , It's the same as not specified ！

printf("a=%*f",13,a);
 Output ：a= Space... Space 123.000000
 The default is after the decimal point 6 position . And it will definitely output all 10 position ,
 be left over 3 position , So fill in the front 3 A space ( The decimal point is one place )

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(4) %.*f( significance ： Specify the digits after the decimal point , Follow %.nf It's the same )

 You'll see 

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(5)%*s( significance ： Also add a space in front according to the actual situation )

char *a="123456";
printf("a=%*s",5,a);
 Output ：a=123456; because 5<6, So it's the same as not specified 

printf("a=%*s",10,a);
 Output ：a= Space... Space 123456

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(6)%.*s( significance ： Specify to intercept the first few digits )

char *a="123456";
printf("a=%.*s",4,a);
 Output ：a=1234;
 Intercept the front 4 digit 

printf("a=%.*s",10,a);
 Output ：a=123456
 Intercept the front 10 digit , Because only 6 position ,
 So it's the same as not specified ！

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1.【 Gentlemen and ladies stop ！！！！】

If you have enough time, you can see my following wordiness ：

0. Necessary introductory knowledge ：

For you to eat the theory I will talk about later , Please read the following little knowledge you may never think about ： 

What does that mean ？ It means ： You need it scanf Split some parameters into two parts to see ！ Many beginners will forget to add addressing characters &, Because no one told him that the parameters in the second part used the address

Example 1：

scanf("%d%d%d"); This is actually possible . Express ： You can enter three values , But because the parameter in the second part is empty , That is, there is no address ,( Such as &, The pointer ), So the input value will not be saved in memory

Example 2：

int a,b,c; scanf("",&a,&b,&c); It's ok . Express ： You can type 0 Number , Because the parameters in the first part do not %, So there is no chance to input , How to save ？ So behind it is a lonely .

Example 3：1+2

The above two examples add up to be really useful . So you often see this form ： int a,b,c; scanf("%d%d%d",&a,&b,&c); You are really familiar with this form ！ Express ： From left to right ： first %d The input number is stored in the memory address a the second %d The input number is stored in the memory address b Third %d The input number is stored in the memory address c

1. On the subject 1：scanf

Use examples to reason ：

(1) %*d Shot dead ：



As shown in the figure , If it does %*, Will draw the next one % Team up illegally with her , Then follow &a matching .

however 《 National Marriage Law 》 Regulations , One person can only have one . therefore , It is stipulated here ： The initiator of the illegal team %*d He was pulled out and shot by the report , Finally, leave the second and &a matching ( Because it matches from left to right ). therefore c There is no object .

in other words ： Turned out to be a My wife was shot therefore ： Turned out to be b My wife married a Turned out to be c My wife married b Eventually lead to c No wife ,c crying . therefore , You type 12 34 56 Then the output a,b,c, result ： a=34,b=56,c=0( The default value is 0)

Excuse me, ： The following form , Which and which illegal team ？

int a=0,b=0,c=0;
        ①  ② ③
scanf("%d%*d%d",&a,&b,&c);

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answer ：②③ Illegal team formation , because * After a Just to win over her last team ！

(2) 【%.*d 】 My teammate was shot ：

Bearing on the ： The above example explains %*d The situation of , We know their secret illegal formation . namely ：

int a=0,b=0,c=0;
        ①  ② ③
scanf("%*d%d%d")：①② organize a team ,① Be shot 
scanf("%d%*d%d")：②③ organize a team ,② Be shot 
scanf("%d%d%*d")：③ Team up with the air ,③ Be shot 

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Under the rev. ： This situation ：%.*d What's going on ？ In fact, the truth is the same , It's illegal to form teams , But this time .* Not simple , So it won't be shot , But her teammate was shot ：

int a=0,b=0,c=0;       
        ①   ② ③
scanf("%.*d%d%d")：①② organize a team ,② Be shot 
scanf("%d%.*d%d")：②③ organize a team ,③ Be shot 
scanf("%d%d%.*d")：③ Team up with the air , The air was shot 

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So the third kind is equivalent to not adding .*, It's exactly equivalent to ： scanf(“%d%d%d”); You can use either of these two . But wise you , You should choose the simplest second .

2. On the subject 2：printf I won't talk about it , Ahead 【 Preface 】 It seems to be very clear .

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