I want to read a string from two files and output it to a new file alternately with the first line of the file, the first line of the file, the second line of the file, and the second line of the file.

I'd like to read strings from two files and output them to the new file alternately with the first line of the file, the first line of the file, the second line of the file, and the second line of the file.
I have three string arrays in my head, starting with the first file

#include<stdio.h>

int main(void){
    FILE*fp1,*fp2,*fp3;
    fp1 = fopen("1.txt", "r");
    fp2 = fopen("2.txt", "r");
    fp3 = fopen("4.txt", "w");

    inti = 0, j = 0;
    int n = 0, m = 0;
    chars[20][20];
    chat[20][20];
    charst [20][20];

    while(fscanf(fp1, "%s", s[i][20])!=NULL){
        st[2*i][20]=s[i][20];
        i++;
    }

    while(fscanf(fp2, "%s", t[j][20])!=NULL){
        st[2*(1+j)][20] = t[j][20];
        j++;
    }

    while(st[n][20]!=NULL){
        fprintf(fp3, "%s\n", st[n][20]);
        n++;
    }

    printf("Outputed";

    fclose(fp1);
    fclose(fp2);
    fclose(fp3);
    return 0;
}

c++

2022-09-30 20:17

2 Answers

The string is std:string
Reading the file is std::ifstream and exporting is std::ofstream
One-line loading is std::getline
Any write is operator<<, with the end-of-line symbol std::endl
Stream objects can be determined for errors by performing bool evaluation, i.e., still readable
Stream objects are automatically closed when they are used up

If you incorporate the area,

#include<fstream>
# include <iostream>
# include <string>

int main() {
    std::ifstream f1 {"1.txt"}, f2 {"2.txt"};
    std::ofstream f3 {"4.txt"};
    for(std::string line; f1||f2;){
        if(f1&getline(f1,line))
            f3<<line<<std::endl;
        if(f2&getline(f2,line))
            f3<<line<<std::endl;
    }
}

That's about it.

2022-09-30 20:17

If you want to do it in the C range instead of C++, you will see the following:

fgets reads a line into the buffer (buf) and returns the string if successful.Returns NULL if it cannot be read due to file termination.Newline characters are also buffered.
http://www.c-tipsref.com/reference/stdio/fgets.html

Write a string with fputs.
http://www.c-tipsref.com/reference/stdio/fputs.html

#include<stdio.h>

int main()
{
    FILE*fp1,*fp2,*fp3;

    constint BUF_SIZE=20;
    char buf [BUF_SIZE];

    char*sz1,*sz2;

    fp1 = fopen("1.txt", "r");
    fp2 = fopen("2.txt", "r");
    fp3 = fopen("4.txt", "w");


    while(true)
    {
        sz1 = fgets(buf,BUF_SIZE,fp1);
        if(sz1!=NULL){
            fputs(sz1,fp3);
        }
        sz2 = fgets(buf,BUF_SIZE,fp2);
        if(sz2!=NULL){
            fputs(sz2,fp3);
        }
        if(sz1==NULL&&sz2==NULL){
            break;
        }
    }

    fclose(fp1);
    fclose(fp2);
    fclose(fp3);

    return 0;
}

This code does not handle errors.
Also, more than 19 bytes of lines have unintended consequences.

If you can fully use C++, please refer to Sayuri's answer.There is no limit to the length of the line, and you can feel safe in the event of an error.

2022-09-30 20:17

If you have any answers or tips

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