Copy a file in reverse order : File Copy « File « C / ANSI-C

1. C / ANSI-C
2. File
3. File Copy

Copy a file in reverse order

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
  long loc;
  FILE *in, *out;
  char ch;


  if(argc != 3) {
    printf("Usage: revcopy <source> <destination>.\n");
    exit(1);
  }

  if((in = fopen(argv[1], "rb")) == NULL) {
    printf("Cannot open input file.\n");
    exit(1);
  }
  if((out = fopen(argv[2], "wb"))==NULL) {
    printf("Cannot open output file.\n");
    exit(1);
  }

  /* find end of source file */
  fseek(in, 0L, SEEK_END);
  loc = ftell(in);

  /* copy file in reverse order */
  loc = loc-1; /* back up past end-of-file mark */
  
  while(loc >= 0L) {
    fseek(in, loc, SEEK_SET);
    ch = fgetc(in);
    fputc(ch, out);
    loc--;
  }
  fclose(in);
  fclose(out);

  return 0;
}

           
       

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