line by line adding - c

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.