/*=======================================================*/
#include <stdio.h>
#include <string.h>

#define MAX_FILENAME_LEN 128
#define MAX_LINE_LEN 80

/*=======================================================*/
void diff(FILE *infile1, FILE *infile2, FILE *outfile);

/*=======================================================*/
int main(void)
{
    /* Declare variables needed for input and output files */
    char filename1[MAX_FILENAME_LEN] = "";
    char filename2[MAX_FILENAME_LEN] = "";
    char outputfile[MAX_FILENAME_LEN] = "";
    FILE *infile1 = NULL;
    FILE *infile2 = NULL;
    FILE *output_file = NULL;

    /* Find out what files should be involved */
    printf("Please enter the name of input file 1\n");
    scanf("%s", filename1);
    printf("%s\n", filename1);
    printf("Please enter the name of input file 2\n");
    scanf("%s", filename2);
    printf("%s\n", filename2);
    printf("Please enter the name of output file \n");
    scanf("%s", outputfile);
    printf("%s\n", outputfile);


    /* Open the specified files */
    infile1 = fopen(filename1, "r");
    infile2 = fopen(filename2, "r");
    output_file = fopen(outputfile, "w");



    /* Change to Put the first line in the output file */
    fprintf(output_file, "File 1 is %s; File 2 is %s\n",
            filename1, filename2);

    /* Do the diff on the files */
    diff(infile1, infile2, output_file);

    /* Close the files */
    fclose(infile1);
    fclose(infile2);
    fclose(output_file);

    return 0;
}

/*=======================================================*/
void diff(FILE *infile1, FILE *infile2, FILE *outfile)
{
    char file1_line[MAX_LINE_LEN] = "";
    char file2_line[MAX_LINE_LEN] = "";
    int line_number = 0;
    int num_differences = 0;
    int v;

    /* Read a line from each file */
    fgets(file1_line, MAX_LINE_LEN, infile1);
    fgets(file2_line, MAX_LINE_LEN, infile2);

    /* Change this into a loop through the infiles */
    for (line_number=1; line_number<=MAX_LINE_LEN; line_number++)
    {

    v = strcmp (file1_line, file2_line);
    if (v != 0)
    {
    fprintf(outfile, "File 1 (%d):%s",
           line_number, file1_line);
    fprintf(outfile, "File 2 (%d):%s",
           line_number, file2_line);
    num_differences++;

    fgets(file1_line, MAX_LINE_LEN, infile1);
    fgets(file2_line, MAX_LINE_LEN, infile2);
    }
    }

    /* Print the number of differences to the screen */
    printf("Number of differences found: %d\n", num_differences);
}