prog/c/diff.c

/*
 * diff.c prints the first line that differs from two files.
 */
#include <stdio.h>
#include <string.h>

const int MAX = 64;

struct filesLines {
  FILE *fp1;
  FILE *fp2;
  char line1[64];
  char line2[64];
};

/*
 * Get the next two lines from each file;
 */
int getlines (struct filesLines flines)
{

  flines.line1 = fgets (flines.line1, MAX, flines.fp1);
  flines.line2 = fgets (flines.line2, MAX, flines.fp1);
  if (flines.line1 == NULL || flines.line2 == NULL)
    return 0;
  else
    return 1;
}


int
main (int argc, char *argv[])
{

  struct filesLines flines;
  /* while each file has another line */
  if (argc != 3)
    {
      printf("Usage: diff FILE1 FILE2\n");
      return 1;
    }

  /*
   * open the two specified files
   */
  flines.file1 = fopen(argv[1], "r");
  flines.file2 = fopen(argv[2], "r");

  while (getlines(flines)) {
    printf("File1\n %s\n", flines.line1);
    printf("File2\n %s\n", flines.line2);

    /* if the lines differ, print out the first line that differs */
    if (strcmp (flines.line1, flines.line2)) {
      printf("File1\n %s\n", flines.line1);
      printf("File2\n %s\n", flines.line2);
    }
    return 0;
  }
}