line by line adding

Question

I currently have to add, and make it so it goes in an order like this

content of file 1
content of file 2
content of file 1
content of file 2

its currently only writing the contents of one text file into the output file, i cant see where i'm going wrong so any help is greatly appreciated.

**** Edit, hi done some digging and found that this exact question has already been answered, didnt want to get in trouble with mods and couldnt delete, thanks all

Answer 1

You are not storing the stream pointers returned by fopen() and you are not interleaving lines from file1 and file2. Here is how to fix these issues:

    ...
    // file 3
    printf("Please enter the name of the output file : ");
    if (scanf("%s", file3) != 1) {
        printf("input error\n");
        exit(1);
    }    
    FILE *OpenFile = fopen(file1, "r");
    FILE *OpenFile2 = fopen(file2, "r");
    FILE *OpenFile3 = fopen(file3, "w");

    if (OpenFile == NULL || OpenFile2 == NULL || OpenFile3 == NULL) {
        perror("Error opening files");
        printf("Press any key to exit!\n");
        exit(1);
    }

    int c1 = 0, c2 = 0;
    while (c1 != EOF || c2 != EOF) {
        if (c1 != EOF) {
            /* copy a line from file1 */
            while ((c1 = fgetc(OpenFile)) != EOF && c1 != '\n') {
                fputc(c1, OpenFile3);
            }
            fputc('\n', OpenFile3);
        }
        if (c2 != EOF) {
            /* copy a line from file2 */
            while ((c2 = fgetc(OpenFile)) != EOF && c2 != '\n') {
                fputc(c2, OpenFile3);
            }
            fputc('\n', OpenFile3);
        }
    }

    printf("The two files were successfully merged into %s\n", file3);

    fclose(OpenFile);
    fclose(OpenFile2);
    fclose(OpenFile3);
    return 0;

Answer 2

You need to alternate your fgetc calls, not do each loop all at once.

int file2_ok = 1, file_ok = 1;
while (file_ok && file2_ok) {
    if (file2_ok) {
        c = fgetc(OpenFile2);
        if (c == EOF) {
            file2_ok = 0;
        } else {
            fputc(c, OpenFile3);
        }
    }
    if (file_ok) {
        c = fgetc(OpenFile);
        if (c == EOF) {
            file_ok = 0;
        } else {
            fputc(c, OpenFile3);
        }
    }
}

This assumes that the two files have the same number of characters. The question doesn't indicate how they should be merged if they don't match up evenly.

Answer 3

This merges alternates lines of two text files. The input files and the output file are program arguments.

#define _CRT_SECURE_NO_WARNINGS

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[]){
    FILE *OpenFile;
    FILE *OpenFile2;
    FILE *OpenFile3;
    char buffer[10000];                     // hopeful
    int finished = 0;

    if(argc < 4) {
        exit(1);
    }
    OpenFile  = fopen(argv[1], "rt");       // "t" is for MSVC
    OpenFile2 = fopen(argv[2], "rt");
    OpenFile3 = fopen(argv[3], "wt");
    if(OpenFile == NULL || OpenFile2 == NULL || OpenFile3 == NULL) {
        exit(1);
    }

    while(finished != 3) {
        if(fgets(buffer, sizeof buffer, OpenFile) != NULL) {
            fputs(buffer, OpenFile3);
        }
        else {
            finished |= 1;
        }

        if(fgets(buffer, sizeof buffer, OpenFile2) != NULL) {
            fputs(buffer, OpenFile3);
        }
        else {
            finished |= 2;
        }
    }

    fclose(OpenFile);
    fclose(OpenFile2);
    fclose(OpenFile3);
    return 0;
}

Input file 1:

File 1 line 1
File 1 line 2
File 1 line 3
File 1 line 4

Input file 2:

File 2 line 1
File 2 line 2

Output file 3:

File 1 line 1
File 2 line 1
File 1 line 2
File 2 line 2
File 1 line 3
File 1 line 4

The solution could be more efficient if it took notice of the finished status instead of calling fgets after any file has reached EOF.