I would like to ask everyone for advice: How to use C language to convert text files?

Please tell me how to convert this txt document using C language

This can be easily solved using STL. It has been commented. If it is not clear yet, learn STL.

#include

#include

#include

using namespace std;

void main()

{

ifstream in(＂F:\\in.txt＂); //The file is in drive F and open it

int key; //corresponds to odd values

double value; //corresponds to even number

pair ar; //Declare key-value pair variables

map maplist; //Create map list

cout

while (in>>key>>value) //Read data

{

cout

ar=make_pair(key,value);//Create key-value pair

maplist.insert(ar); //Insert into maplist, this container is automatically sorted by key value

}

in.close();

ofstream out(＂F:\\out.txt＂)；//Output file

cout

for(map::const_iterator temp = maplist.begin(); temp != maplist.end(); temp )

{

out

cout

}

out.close();

getchar();

}

If you use C language to solve the problem, you can create a structure containing two values, then create an array or linked list of this structure to store the read data, then sort by the first value in the structure, and finally output.

C language output to text document problem

#include

void Calculator()

{

int a,b,c,d;

char x,y;

FILE *fp1,*fp2;

fp1=fopen("expres.txt","r");

fp2=fopen("result.txt","w");

printf(＂Please input\n＂);

fscanf(fp1,"%d%c%d",&a,&x,&b);

fprintf(fp1,"%d%c%d\n",a,x,b);

switch (x)

{

case ' ':

c=a b;

printf(＂%d%c%d=%d\n＂,a,x,b,c);

fprintf(fp2,"%d%c%d=%d\n",a,x,b,c);

break;

case '-':

c=a-b;

printf(＂%d%c%d=%d\n＂,a,x,b,c);

fprintf(fp2,"%d%c%d=%d\n",a,x,b,c);

break;

case '*':

c=a*b;

printf(＂%d%c%d=%d\n＂,a,x,b,c);

fprintf(fp2,"%d%c%d=%d\n",a,x,b,c);

break;

case '/':

c=a/b;

printf(＂%d%c%d=%d\n＂,a,x,b,c);

fprintf(fp2,"%d%c%d=%d\n",a,x,b,c);

break;

default:

printf(＂Input Error!\n＂);

break;

}

}

int main()

{

Calculator();

return 0;

}

The complete code is like this, then you create a new express.txt yourself and enter the expression in it, such as 3 4

Then run, it will output 3 4=7

in result.txt

How to output files in C language

1. The C language standard library provides a series of file operation functions. File operation functions are generally named in the form of the word f (f is the abbreviation of file), and their declaration is located in the stdio.h header file. For example: fopen and fclose functions are used to open and close files; fscanf and fgets functions are used to read files; fprintf and fputs functions are used to write files; ftell and fseek functions are used to obtain and set file operation positions. General C language tutorials have a chapter on file operations. You can find this textbook for further study.

2. Routine:

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

twenty one

twenty two

twenty three

twenty four

#include

inta;

charb,c[100];

intmain(){

FILE* fp1 = fopen("input.txt", "r"); //Open the input file

FILE* fp2 = fopen("output.txt", "w"); //Open the output file

if(fp1==NULL || fp2==NULL) {//Exit if opening the file fails

puts("Cannot open file!");

rturn 0;

}

fscanf(fp1,"%d",&a); //Read an integer from the input file

b=fgetc(fp1); //Read a character from the input file

fgets(c,100,fp1); //Read a line of string from the input file

printf("%ld",ftell(fp1));//Output the offset number of bytes of the current position of the fp1 pointer relative to the beginning of the file

fputs(c,fp2); //Write a line of string to the output file

fputc(b,fp2); //Write a character to the output file

fprintf(fp2,"%d",a); //Write an integer to the output file

fclose(fp1);//Close the input file

fclose(fp2);//Close the output file, which is equivalent to saving

return0;

}

How to write the output results of the c program to a txt file

#include

#include

int IsLeapYear(int year)

{

if((year%4==0&year 0!=0)||(year@0==0))

return 1;

else

return 0;

}

int month_day(int year,int month)

{

int mon_day[]={31,28,31,30,31,30,31,31,30,31,30,31};

if(IsLeapYear(year)&month==2)

return 29;

else

return(mon_day[month-1]);

}

int DaySearch(int year,int month,int day)

{

int c=0;

float s;

int m;

for(m=1;mc=c month_day(year,m);

c=c day;

s=year-1 (float)(year-1)/4 (float)(year-1)/100 (float)(year-1)/400-40 c;

return ((int)s%7);

}

int PrintAllYear(int year)

{

int temp;

int i,j;

FILE *fp;

if((fp=fopen(＂year.txt＂,＂wt＂))==NULL)

{

printf(＂cannot open file\n＂);

return 1;

}

fprintf(fp,＂\n\n%d year\n＂,year);

for(i=1;i

{

temp=DaySearch(year,i,1);

if(i==1)

{

if(temp==0) fprintf(fp,＂\n first day is %d\n＂,7);

else fprintf(fp,＂\n first day is %d\n＂,temp);

}

fprintf(fp,＂\n\n%d month\n＂,i);

fprintf(fp,＂ S M T W T F S \n＂);

for(j=1;j

{

if(j-temp

fprintf(fp,＂ ＂);

else

fprintf(fp,＂=＂,j-temp);

if(j%7==0)

fprintf(fp,＂\n＂);

}

}

fclose(fp);

return 0;

}

void main()

{

int year;

printf(＂\nPlease input a year(XXXX)＂);

scanf(＂%d＂,&year);

PrintAllYear(year);

}

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