From:	Jim Barlow <Jim_Barlow AT bc DOT sympatico DOT ca>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Newbie question -- debug this plz
Date:	Sat, 11 Jul 1998 18:24:59 -0700
Organization:	BCTEL Advanced Communications
Lines:	41
Message-ID:	<35A8106A.6B1FD58D@bc.sympatico.ca>
Reply-To:	Jim_Barlow AT bc DOT sympatico DOT ca
NNTP-Posting-Host:	vcta01m06-157.bctel.ca
Mime-Version:	1.0
To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Okay... I feel really stupid asking this and should be well below me, but I've
never had much experience with file i/o in C/DJGPP.

I'm trying to write a program that does this (again, C, DJGPP):
1) takes the first command line parameter as a filename (obvious)
2) opens the file. coughs up an error if any.  File is binary and can contain
nulls in-line. Also very large (~500 kb).
3) reads the file into a buffer.  Search for a specific string.  If found it
needs to be able to write to that offset.
4) write changes to the file without corrupting anything.  It's overwritting
information, not inserting anything new.

FILE *fp;
char *my_buffer, *offset;
if (argc) {
  fp = fopen (argv[1], "rb+"); // or whatever open for read/write binary is
  if (ferror (fp)) {
    printf ("There was an error...");
    return;
  }
  // best way to read the data into my_buffer?
  my_buffer = offset = (char *)malloc (sizeof(char) *
func_that_gets_file_size(fp));
  readinto(fp); // should i use fread() or something else?

  strchr (offset, "my_string");
  if (offset) {
    strcpy (offset, "newstring");
  }
  // write buffer to file
}

Thanks for your patience.
--
J Barlow
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