Here is source code of the C Program to append the content of file at the end of another. The C program is successfully compiled and run on a Linux system. The program output is also shown below.

/*
* C Program to Append the Content of File at the end of Another
*/
#include <stdio.h>
#include <stdlib.h>

main()
{
FILE *fsring1, *fsring2, *ftemp;
char ch, file1[20], file2[20], file3[20];

printf("Enter name of first file ");
gets(file1);
printf("Enter name of second file ");
gets(file2);
printf("Enter name to store merged file ");
gets(file3);
fsring1 = fopen(file1, "r");
fsring2 = fopen(file2, "r");
if (fsring1 == NULL || fsring2 == NULL)
{
perror("Error has occured");
printf("Press any key to exit...\n");
exit(EXIT_FAILURE);
}
ftemp = fopen(file3, "w");
if (ftemp == NULL)
{
perror("Error has occures");
printf("Press any key to exit...\n");
exit(EXIT_FAILURE);
}
while ((ch = fgetc(fsring1)) != EOF)
fputc(ch, ftemp);
while ((ch = fgetc(fsring2) ) != EOF)
fputc(ch, ftemp);
printf("Two files merged %s successfully.\n", file3);
fclose(fsring1);
fclose(fsring2);
fclose(ftemp);
return 0;
}



$ cc pgm47.c
$ a.out
Enter name of first file a.txt
Enter name of second file b.txt
Enter name to store merged file merge.txt
Two files merged merge.txt successfully.