/*
bgsub.c 1.0.1 (2002-Jan-29-Tue)
Adam M. Costello
http://www.nicemice.net/amc/

bgsub <old> <new>

Copies stdin to stdout, globally substituting the string <new> for the
string <old>.  The input stream and the arguments may contain binary
data, but the arguments cannot contain zero-bytes (NUL characters).

*/

/* This is ANSI C code. */


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


static char *progname = NULL;


void fail(void)
{
  perror(progname);
  exit(EXIT_FAILURE);
}


void usage(void)
{
  fprintf(stderr,
          "usage:\n"
          "%s <old> <new>\n"
          "Copies stdin to stdout, "
          "globally substituting <new> for <old>.\n",
          progname);
  exit (EXIT_FAILURE);
}


int main(int argc, char **argv)
{
  unsigned char *old, *new, *lookingfor, *p;
  int c;

  progname = strrchr(argv[0], '/');
  if (!progname) progname = argv[0];
  else ++progname;

  if (argc != 3) usage();

  old = (unsigned char *) argv[1];
  new = (unsigned char *) argv[2];
  lookingfor = old;

  for (;;) {
    c = getchar();

    if (c == *lookingfor) {
      if (!*++lookingfor) {
        if (fputs((char *) new, stdout) == EOF) fail();
        lookingfor = old;
      }
    }
    else {
      for (p = old;  p != lookingfor;  ++p) {
        if (putchar(*p) == EOF) fail();
      }

      lookingfor = old;
      if (c == EOF) break;
      else if (putchar(c) == EOF) fail();
    }
  }

  exit(EXIT_SUCCESS);
}