Write a program to compare two files, printing the first line where they differ.
Here's Rick's solution:
/******************************************************
KnR 7-6
--------
Write a program to compare two files and print the
first line where they differ.
Author: Rick Dearman
email: rick@ricken.demon.co.uk
Note: This program prints ALL the lines that are
different using the <> indicators used by
the unix diff command. However this program
will not cope with something as simple as a
line being removed.
In reality the program would be more useful
if it searched forward for matching lines.
This would be a better indicator of the simple
removal of some lines.
This has lead me to track down a version of the
"diff" command available on GNU/Linux systems.
for more information go to the web site at:
www.gnu.org
******************************************************/
#include <stdio.h> #include <string.h> #define MAXLINE 1000 void diff_line( char *lineone, char *linetwo, int linenumber ) { if(strcmp (lineone, linetwo) < 0 || strcmp (lineone, linetwo) > 0) printf( "%d<%s %d>%s ", linenumber, lineone, linenumber, linetwo); } int main(int argc, char *argv[] ) { FILE *fp1, *fp2; char fp1_line[MAXLINE], fp2_line[MAXLINE]; int i; if ( argc != 3 ) { printf("differ fileone filetwo "); exit(0); } fp1 = fopen( argv[1], "r" ); if ( ! fp1 ) { printf("Error opening file %s ", argv[1]); } fp2 = fopen( argv[2], "r" ); if ( ! fp2 ) { printf("Error opening file %s ", argv[2]); } i = 0; while ( (fgets(fp1_line, MAXLINE, fp1) != NULL) && (fgets(fp2_line, MAXLINE, fp2) != NULL)) { diff_line( fp1_line, fp2_line, i ); i++; } return 0; }
and here's "flippant squirrel"'s solution:
/* Exercise 7-6 - write a program to compare two files, printing the first line
* where they differ
*
* Note : I amended this a bit...if a file is shorter than the other, but is identical
* up to that point, the program prints out "EOF" as the string that's not equal.
*
*/
#include <stdio.h> #include <stdlib.h> #include <string.h> #define BUFF_SIZE 1000 /* uses fgets, removes the ' ' at the end of the string if it exists */ char *safegets(char *buffer, int length, FILE *file) { char *ptr; int len; if (buffer != NULL) { ptr = fgets(buffer, length, file); if (ptr != NULL) { len = strlen(buffer); if (len > 0) { if (buffer[len - 1] == ' ') { buffer[len - 1] = '